norton 750 commando

CHAPTER ONE

GENERAL INFORMATION

This handbook covers all service operationsfor late-model Norton twins—from changing aspark plug to overhauling an engine. The infor-mation applies specifically to the followingmodels:

750 Commando — Standard

750 Commando — Combat

850 Commando Mark II and Mark IIA

850 Commando Mark III

(Electric Start)

In addition, the majority of the engine andtransmission service procedures, as well as thosefor the front and rear suspension units and drumtypes brakes, are applicable to the earlier750 G15 CS and the 750 Atlas. To further aidservicing of these early models, an engine ex-ploded view is included in addition to electricalsystem schematics.

A WORD OF CAUTION

The large-displacement Norton twin is a high-performance motorcycle designed for high-speedtouring and open-class production racing. Assuch, it represents a total design approach; en-gine performance, chassis geometry, and com-ponent selection are all carefully integrated toprovide not only high performance but safe

performance as well. Alterations to or substitu-tion of suspension and brake components in anattempt to improve a late model or update anearly one are not recommended. Changes inwheelbase, trail, caster, center of gravity, etc.,resulting from uninformed chassis modificationcan render the motorcycle unsafe.

PARTS ORDERING

To prevent inadvertent installation of an in-correct part, always state your motorcycle'sserial number when ordering replacement com-ponents. In this way your dealer can determinethe correct part. Your motorcycle will be saferand more enjoyable as a result.

SERVICE HINTS

Most of the service procedures described canbe performed by anyone reasonably handy withtools. However, carefully consider your owncapabilities before attempting any operationwhich involves major disassembly of the engineor transmission.

Some operations, for example, require the useof a press. It would be wiser to have them per-formed by a shop equipped for such work, ratherthan to try the job yourself with makeshift equip-ment. Other procedures require precision meas-urements. Unless you have the skills and

CHAPTER ONE

equipment to make them, it would be better tohave a motorcycle shop do the work.

Repairs are faster and easier if the motorcycleis clean before you begin work. There are specialcleaners for washing the engine and relatedparts. Just brush or spray on the solution, let itstand, then rinse it away with a garden hose.Clean all oily or greasy parts with cleaningsolvent as you remove them. Never use gasolineas a cleaning agent. It presents an extreme firehazard. Always work in a well-ventilated areawhen using cleaning solvent. Keep a fire extin-guisher, rated for gasoline fires, handy just incase of emergency.

Special tools are required for some serviceprocedures. Some of these may be purchasedthrough Norton dealers. If you are on goodterms with the dealer's service department, youmay be able to borrow his.

Much of the labor charge for repairs made bydealers is for removal and disassembly of otherparts to reach the defective one. It is frequentlypossible to do all this yourself, then take theaffected subassembly to the dealer for repair.

Once you decide to tackle a job yourself, readthe entire section in this handbook pertaining toit. Study the illustrations and the text until you

have a thorough idea of what's involved. If spe-cial tools are required, make arrangements toget them before you begin work. It's frustratingto get part way into a job and then discover thatyou are unable to complete it.

TOOLS

To properly service your motorcycle, you willneed an assortment of ordinary hand tools. As aminimum, these include:

1. Combinationwrenches

2. Socket wrenches3. Plastic mallet4. Small hammer5. Snap ring pliers6. Phillips

screwdrivers

7. Slot screwdrivers8. Impact driver9. Pliers

10. Feeler gauges11. Spark plug gauge12. Spark plug wrench13. Dial indicator14. Drift

An original equipment tool kit, like the oneshown in Figure 1, is available through mostNorton dealers and is suitable for most minorservicing.

Electrical system servicing requires a volt-meter, ohmmeter or other device for determiningcontinuity, and a hydrometer for the battery.

GENERAL INFORMATION

There are only 3 essential special tools re-quired for working on the Norton — clutchspring compressor. Figure 69, Chapter Four;engine sprocket puller, Figure 73, ChapterFour; and a C wrench for removing and tight-ening the exhaust headpipe nuts.

EXPENDABLE SUPPLIES

Certain expendable supplies are required.These include grease, oil, gasket cement, liquidfastener-locking compound, rags, and cleaningsolvent. These items are available at most motor-cycle shops artd auto supply stores. Distilledwater for batteries is available at supermarkets.

SAFETY FIRST

A professional mechanic can work for yearsand never sustain a serious injury. If you observea few rules of common sense and safety, you canenjoy many hours safely servicing your ownmachine. You can also hurt yourself or damageyour motorcycle if you ignore these rules.

1. Never use gasoline as a cleaning solvent.2. Never smoke or use a torch around flam-mable liquids, such as cleaning solvent.3. Never smoke or use a torch in areas wherebatteries are being charged. Highly explosivehydrogen gas is formed during the chargingprocess. And never arc the terminals of a batteryto see if it has a charge; the sparks can ignite theexplosive hydrogen as easily as would anopen flame.4. If welding or brazing is required on themotorcycle, remove the fuel tank and set it a safedistance away—at least 50 feet.5. Always use the correct size wrench for turn-ing nuts and bolts, and when a nut is tight, thinkfor a moment what would happen to your handif the wrench were to slip.6. Keep your work area clean and uncluttered.7. Wear safety goggles in all operations involv-ing drilling, grinding, the use of a chisel, or anair hose.8. Don't use worn tools.9. Keep a flre extinguisher handy. Be sure it israted for gasoline and electrical flres.

CHAPTER TWO

PERIODIC MAINTENANCE AND LUBRICATION

Regular maintenance is the best guarantee ofa trouble-free, long-lasting motorcycle. An after-noon spent now, cleaning and adjusting, canprevent costly mechanical problems in the fu-ture and unexpected breakdowns on the road.

The procedures presented in this chapter canbe easily carried out by anyone with averagemechanical skills. The operations are presentedstep-by-step and if they are followed, it is diffi-cult to go wrong.

SERVICE INTERVALS

The services and intervals shown in Table 1are recommended by the factory. Strict adher-ence to these recommendations will go a longway in ensuring long service life from yourNorton.

For convenience in maintaining your motor-cycle, most of the services shown in the tableare described in this chapter. However, someprocedures which require more than minor dis-assembly or adjustment are covered elsewherein this book as indicated.

TIRE PRESSURE

Tire pressures should be checked and ad-justed to accommodate rider and luggage weight.A simple, accurate gauge can be purchased for

a few dollars and should be carried in the motor-cycle tool kit. The appropriate tire pressures areshown in Table 2.

BATTERY ELECTROLYTE LEVEL

The battery is the heart of the electrical sys-tem. It should be checked and serviced as indi-cated. The majority of electrical system troublescan be attributed to neglect of this vitalcomponent.

The electrolyte level may be checked with thebattery installed. However, it's necessary to re-move the left cover plate (Figure 1). The electro-lyte level should be maintained between the 2marks embossed on the battery case (Figure 2).If the electrolyte level is low, it's a good idea toremove the battery from the motorcycle so thatit can be thoroughly serviced and checked.

1. On 750 and 850 Mark II models, slide themetal loops off the hold-down bar and removethe bar (Figure 3). On 850 Mark III models,disconnect the battery strap buckle from thehook on the battery carrier (Figure 4).2. Disconnect the electrical leads from the bat-tery terminals—first the positive (ground) andthen the negative (Figure 5).

3. Disconnect the vent pipe and lift the batteryout of the holder.


Table 1 SERVICE INTERVALS

Weekly

Every 2 weeks

Every 250 miles

Every 1,000 miles

Every 2,500-3,000* miles

Every 5,000-6,000* miles

Every 10,000-12,000* miles

Check tire pressure

Check battery electrolyte level

Check engine oil tank level

Check primary chaincase oil levelAdjust rear chainLubricate all control cables with oilAdjust both brakes (optional disc brake is non-adjustable)Check disc brake fluid levelExamine disc brake pads for wear

Check timing and adjust contact breaker pointsClean spark plugs and set gapsChange primary chaincase oilCheck clutch adjustmentCheck primary chain adjustmentChange engine oilLubricate and adjust rear chainCheck gearbox oil levelCheck front and rear rubber engine mountings for side playChange oil in forksGrease rear brake pedal pivotCheck isolastic mountings for free-play

Change gearbox oilReplace oil filter elementClean contact breaker pointsLubricate contact breaker cam felt and auto advance unitGrease brake expander pivots (one stroke of grease gun)Check and adjust valve rocker clearancesCheck and adjust camshaft chainFit new air fitter elementCheck and oil swinging arm bushings

Repack wheel bearings (including the rear wheel sprocketbearing) with grease

Dismantle and clean both carburetors and check for wear

E .

•Longer intervals correspond to factory-recommended intervals for 850 Mark ii and Mark Mi models.

6

Load

Rider only(approx. 170 Ib.)

Rider and passenger(approx. 340 Ib.)

Rider and passengerplus 100 Ib. luggage

(approx. 440 Ib.)

Table 2 TIRE PRESSURES

FrontRear

FrontRear

FrontRear

CHAPTER TWO

Pressure*

24psi(1.7Kg/sq.cm)26 psi (1.8 Kg/sq. cm)

26 psi (1.8 Kg/sq. cm)28 psi (1.969 Kg/sq. cm)

28 psi (1.969 Kg/sq. cm)32 psi (2.250 Kg/sq. cm)

*Dunlop only—Avon min. 26 psi front and rear.


CAUTIONBe careful not to spill battery electro-lyte on painted or polished surfaces.The liquid is highly corrosive and willdamage the finish.

4. Remove the caps from the battery cells andadd distilled water to correct the level. Neveradd electrolyte (acid) to correct the level.

5. After the level has been corrected and thebattery allowed to stand for a few minutes, checkthe specific gravity of the electrolyte in each cellwith a hydrometer. Follow the hydrometer man-ufacturer's instructions for reading the instru-ment. The specific gravity should be 1.270-1.290at a temperature of 60°F. If it is substantiallyless, charge the battery at a rate of one amperefor at least 4 hours or until the specific gravityis at an acceptable level.

WARNINGDuring charging, highly explosive hy-drogen gas is released from the battery.The battery should be charged only ina well-ventilated area, and open flamesand lighted cigarettes should be kept

H

CHAPTER TWO

away. Never check the charge of thebattery by arcing across the terminals;the resulting spark can ignite thehydrogen gas.

6. Connect the positive charger lead to the posi-tive battery terminal and the negative chargerlead to the negative battery terminal.

NOTE: The battery may be connectedto a charger using the electrical outleton the right side of the motorcycle(Figure 6). The plug should be wiredas shown in Figure 7. The battery leadson the motorcycle must be connected.

7. Remove the vent caps from the battery, setthe charger at 12 volts, and switch it on. If theoutput of the charger is variable, it's best toselect a low setting—n/2 to 2 amps.

8. After the battery has been charged forabout 8 hours, turn off the charger, disconnectthe leads, and check the specific gravity. Itshould be within the limits specified above. If itis, and if it remains stable after one hour, thebattery is charged.

9. Clean the battery terminals and case, and re-install it in the motorcycle, reversing the removalsteps. Coat the terminals with Vaseline or sili-cone spray to retard decomposition of theterminal material.

ENGINE OIL

Checking Level

Engine oil level is checked with the dipstickmounted in the tank filler cap (Figure 8).


1. Start the engine and allow it to run for acouple of minutes so that the excess oil will bereturned from the crankcase to the oil tank.

2. Remove the seat and unscrew the filler capfrom the oil tank. Visually check to see that theoil is circulating in the tank. Replace the fillercap to prevent oil from being splashed out.

3. Shut off the engine and allow the oil to settlein the tank. Then, check the level with the dip-stick. The oil level should be above the "L"mark but not above the "H" mark (Figure 9);if the level is above the "H" mark, oil will over-flow into the air filter. If necessary, add therecommended grade of oil to correct the level.Install the filler cap and tighten it securely.

Changing

The factory recommended oil change intervalis 2,500-3,000 miles. This assumes that themotorcycle is operated in moderate climates. Inextremely cold climates, oil should be changedevery 30 days. The time interval is more impor-tant than the use interval because acids formedby gasoline and water vapor from condensationwill contaminate the oil even if the motorcycleis not run for several months. Also, if the motor-cycle is operated under dusty conditions the oilwill get dirty more quickly and should bechanged more frequently than recommended.

Use only a detergent oil with an API ratingof SE or better. The quality rating is stamped on

the top of the can. Try always to use the samebrand of oil. Oil additives are not recommended.

A 50W oil is recommended for use at am-bient temperatures above 0°F (—18°C).

1. Start the engine and run it until it is warm.Then shut it off.2. Remove the seat and the right side cover(Figure 10).

B

3. Remove the drain plug from the oil tank(Figure 11). On early models, remove the boltwhich attaches the oil filter union to the tank.

4. Remove crankcase drain plug (with IVi in.socket) and sump filter if fitted (Figure 12). Dis-mantle the sump filter (Figure 13) and clean itthoroughly in solvent. Clean the magnetic drainplug. Remove the filter from the oil tank (Fig-ure 14) and thoroughly clean it with solvent.5. Remove and discard the oil filter element(5,000-6,000-mile interval). See Figure 15.6. When the oil has drained, install a new filterelement and a new clamp and reinstall the drain

10 CHAPTER TWO

plugs and tank and sump filters. Fill the oil tankwith fresh oil to the level described earlier (3qts.—U.S.; 5 pts. Imp.—U.K.; 2.8 liters). Startthe engine and run it at a moderate, steadyspeed. Visually check the oil circulation in thetank. Because the sump was drained earlier, the

PERIODIC MAINTENANCE AND LUBRICATION 11

scavenge side of the oil pump will not immedi-ately begin to pump oil back to the tank. Shutthe engine off and allow the oil to settle for acouple of minutes. Recheck the level and correctit if necessary.7. Reinstall the side cover and the seat.

PRIMARY CHAINCASE

The oil level in the primary chaincase shouldbe checked every 1,000 miles and changedevery 2,500 miles.

Checking Level

1. With the motorcycle sitting level, remove thelevel plug from the chaincase (Figure 16). If theoil level is correct, a small amount of oil shouldrun out of the hole.

2. On 750 and 850 Mark II models, if oil doesnot run out, drain and refill the primary case asdescribed below; it is important that the casecontain exactly 7 ounces (200cc) of oil. On 850Mark III models, if oil does not run out, removethe filler cap and slowly add oil (SAE 20W-50)until it begins to run out of the level hole.

3. Reinstall the level plug and the filler cap.See Figure 16.

Changing

1. Remove the left footrest. Place a drip panbeneath the chaincase and remove the centerbolt. Tap along the edges of the chaincase witha soft mallet to break the seal and allow theoil to drain.

2. Remove the chaincase cover and clean it andthe inner case with solvent.

3. Reinstall the chaincase cover and remove thefiller cap and level plug.4. Pour 7 ounces of clean SAE 20W-50 oil intothe chaincase through the filler opening. Wait amoment until the oil ceases to run out of thelevel hole and then install the plug and cap.Reinstall the footrest.

TRANSMISSION

The transmission oil should be checkedevery 2,500 miles and should be changedevery 5,000 miles.

1 . Leve l p l u g 2 . Fill p l u g 3 . C e n t e r bo l t ( e x c e p t Mk III)

12 CHAPTER TWO

Checking Level

1. Remove the level plug from the transmission(Figure 17). If the oil level is correct, a smallamount of oil should run out of the hole.

2. If oil does not run out, remove the filler cap(Figure 18) and slowly add oil (SAE 90 EP) untilit just begins to run out of the level hole.

3. Reinstall the level plug and the filler cap.

Changing

1. Ride the motorcycle for several miles towarm up the oil in the transmission.

2. Place a drip pan beneath the transmission andremove the filler cap and drain plug (Figure 19).

3. After the oil is drained, reinstall the drainplug and fill the transmission with 14.5 ouncesof oil (U.S.); 0.75 pts. Imp. (U.K.); 420cc. Waita few minutes until the oil has drained down intothe transmission. Then remove the level plugand permit the excess oil to drain out.

4. Reinstall the level plug and the filler cap.

SWINGING ARM

Oil in the swinging arm pivot of 750 and 850Mark II models should be checked every 5,000miles and added to if necessary. The oiled wicksused in 850 Mark III models are good for thelife of the swinging arm pivot bushings and needbe replaced only when the bushings are replaced.

1. Remove the spindle locating bolt from thetop of the swinging arm pivot (Figure 20).

2. Use a grease gun filled with SAE 140 oil.Inject oil into the pivot tube through the lubefitting (Figure 21) until it begins to run out ofthe spindle locating bolt hole. If a grease gun isnot available, the lube fitting can be removedand oil added with a pumper-type oil can.


3. Reinstall the spindle locating bolt and thelube fitting (if removed).

FRONT FORK

The damping oil in the front fork should bechanged every 2,500 miles or at any time ex-cessive bouncing of the front end indicates a lowoil level. There is no practical way of checkingand correcting the level; each fork leg must con-tain exactly 150cc (5 ounces) of damping oil ifthe front supension is to operate correctly.

If after the oil has been changed the frontsuspension continues to bounce or ''hobby-horse," a major service may be required. In suchcase, refer to Chapter Ten.1. Turn the front end to left lock, place a drippan beneath the left fork leg, and remove thedrain screw (Figure 22).

2. When the oil has ceased to drain, lock thefront brake and depress the front end severaltimes to expel residual oil. Reinstall drain plug.3. Turn the front end to right lock and drainthe right leg in the same manner as for the left.4. Place a clean shop towel over the gas tank toprotect it.

5. Unscrew the fill plugs (1-5/16 in. socket)from the tops of the fork legs (Figure 23). Wrapa shop rag around each of the instruments andtape them in place to prevent damage to themand the gas tank.6. Lift the front wheel to expose the springs andsupport it with a block of wood (Figure 24).7. Unscrew the filler plugs from the tops of thedamper rods (Figure 25).8. Remove the block from beneath the wheeland fully extend the forks.

9. Fill each fork leg with 150cc (5 ounces) ofany of the oils shown in Table 3. See Figure 26.

14 CHAPTER TWO

Table 3 FORK OIL

Brand

CastrolBP

Shell

Mobil

ESSO

Texaco

Duckham's

Sun Oil

Type

Castrolite lOW 30BP Super Visco-Static l o w 40

Shell Super Motor Oil

Mobiloil Super

Uniflo

Havoline Motor Oil lOW 30

Duckham's Q5500Sunoco Special Motor Oil 20W 50

NOTE: Each leg will probably notaccept all of the oil at first. Cover thetop of the fork tube with your handand pump the slider slowly up anddown to distribute the oil and thenadd more oil until the entire ISOcc hasbeen poured in.


10. Raise and block the wheel once again.Screw the locknuts all the way on to the bottomthread (Figure 27). Slide the instrument mountsover the springs and screw on the filler caps andlock them with the nuts (Figure 28).

HYDRAULIC DISC BRAKE

The hydraulic fiuid level in the disc brakemaster cylinder should be checked every 1,000miles and the brake pads should be checked forwear. Bleeding the hydraulic system, servicingthe master cylinder, caliper, and disc, and re-placing brake pads are covered in Chapter Eight.

Fluid Level

1. Clean the reservoir cap thoroughly with a dryrag and unscrew it. Remove the fiexible bellowsand set it in the upturned cap to prevent it fromgetting dirty (Figure 29).

c

11. Remove the block and lower the frontwheel. Screw in the top caps and tighten themsecurely. Reinstall the handlebars.

2. The fluid level in both brake reservoirsshould be Vi in. (13mm) from the top edge(Figures 30 and 31). If necessary, correct thelevel by adding any DOT 3 approved hydraulicbrake fluid.3. Reinstall the bellows with the closed enddown. Do not pour hydraulic fiuid into the bel-lows. Check the vent hole in the top of thecap to make sure it is open and screw the capon tightly.

CAUTIONBe careful not to spill the brake fiuidon painted surfaces or bring it in con-tact With plastic or rubber components.

Brake Pad Wear

Inspect the brake pads for excessive or unevenwear, scoring, and oil or grease imbedded in

16 CHAPTER TWO

REAR CHAIN

The rear drive chain should be checked andadjusted every 1,000 miles and removed,cleaned, and lubricated every 2,500 miles.

Adjustment

1. Loosen the axle nuts (Figure 32) and thechain adjuster locknuts.

the friction material. If any of these conditionsexist, replace the pads, as a set, as described inChapter Eight.

2. Screw the adjusters either in or out as re-quired, in equal amounts. The free movement ofthe chain, midway between the sprockets, shouldbe 34-1 in. (19-25mm) with a rider seated onthe motorcycle (Figure 33). Rotate the rearwheel to move the chain to another position andrecheck the adjustment; chains rarely wear orstretch evenly and as a result the free-play willnot remain constant over the entire chain. Atits tightest point it should have no less than ¥4 in.free-play and at its loosest the free-play shouldnot be greater than one inch. If the chain cannotbe adjusted within these limits it is excessivelyworn and stretched and should be replaced.

3. When the adjustment is correct, sight alongthe chain from the rear sprocket to see that it iscorrectly aligned. It should leave the top of therear sprocket in a straight line. If it is cocked toone side or the other, the rear wheel is incor-rectly aligned and must be corrected by turningthe adjusters counter to one another until thechain and sprocket are correctly aligned. When


the alignment is correct, readjust the free-playas described above and tighten the adjuster lock-nuts and axle nuts securely.

Cleaning and Lubrication

The rear chain is lubricated by a restrictertype oiler connected to the engine oil tank. Every2,500 miles, remove, thoroughly clean, andlubricate the chain.

1. Disconnect the master link and remove thechain from the motorcycle. If a piece of oldchain is available, connect it to the motorcycle'schain before it is removed and leave the oldchain around the gearbox sprocket to makechain replacement easier.

2. Inspect the chain for excessive wear andstretch. Scribe 2 marks 12V^ in. (317mm) aparton a flat surface. With the chain compressed toits minimum free length, the marks should line

up with pivot pins exactly 20 links apart(Figure 34). When the chain is extended, the 20links should not exceed 12^4 in. (324mm).

3. Immerse the chain in a pan of cleaning sol-vent and allow it to soak for about a half hour.

4. Scrub the rollers and side plates with a stiffbrush and rinse the chain in clean solvent tocarry away loosened grit. Hang up the chain andallow it to dry thoroughly.

5. Lubricate the chain with a good grade ofchain lubricant carefully following the manufac-turer's instructions. As an alternative, lubricateby soaking in a pan of heated all-purpose greasesuch as Castrol Graphited Grease, Shell RetinexA or DC, Mobilgrease MP, or Marfax All-Purpose Grease. Heating permits the grease topenetrate the rollers and pins, but extreme caremust betaken.

WARNINGIf the grease is heated excessively itmay reach its flash point, resulting in adangerous and difficult to extinguishfire. NEVER heat the grease with anopen flame or on a hot plate. Heat itonly by placing the grease pan in alarger pan containing about an inch ofboiling water, and only after the waterhas been removed from the heatsource.

After the chain has soaked in the grease forabout a half hour, remove it from the pan andwipe off all the excess grease with a clean rag.

6. Reinstall the chain on the motorcycle. Use anew clip on the master link and install it so thatthe closed end of the clip faces the direction ofchain travel (Figure 35).

c

20 links = 12.5 inches compressed' 20 ilnks = 12.75 inches extended

18 CHAPTER TWO

7. Adjust the free-play of the chain as describedearlier in this section.

CONTROL CABLES

The control cables, with the exception of theTefion lined throttle cable on 850 Mark IIImodels, should be lubricated every 1,000 miles.In addition, all cables should be adjusted at thisinterval. The cables should be inspected period-ically for fraying and the cable sheaths shouldbe checked for chafing. The cables are expend-able items and should be replaced when foundto be faulty.

Lubrication

The control cables can be lubricated eitherwith oil or with any one of the popular commer-cial cable lubricants and a cable lubricator. Thefirst method requires more time and the completelubrication of the entire cable is less certain.

Oil Method

1. Disconnect the cable from the control (throt-tle grip, clutch lever, etc.).

2. Make a cone from a stiff piece of paper andtape it to the end of the cable sheath (Figure 36).3. Hold the cable upright and pour a smallquantity of light oil into the cone. Work thecable in and out of the sheath for several min-utes to help the oil migrate down between thecable and sheath.

4. Remove the cone, reconnect the cable, andadjust it as described below.

Lubricator Method

1. Disconnect the cable from the control.

2. Attach the lubricator in accordance with themanufacturer's instructions (Figure 37).

3. Insert the lubricant can nozzle in the lubri-cator, press the button on the can, and hold itdown until the lubricant begins to flow out ofthe other end of the cable.


NOTE: On throttle and choke cables,remove the carburetor cap so the lubri-cant will not run into the carburetor.

4. Remove the lubricator, reconnect the cableto the control, and adjust it as described below.

Throttle Cable Adjustmeut

Throttle cable adjustment is described underTune-up at the end of this chapter.

Clutch Cahle Adjustment

There should be 3/16-1/4 in. (4.6-6.3mm)free play in the clutch cable sheath (Figure 38).If this free play cannot be obtained with theadjuster on the clutch control lever, screw theadjuster all the way in and remove the clutchadjuster cover from the primary chaincase(Figure 39) and the inspection cover from thetransmission (Figure 40). Check to see if thereis any movement in the clutch operating lever(Figure 41). If there is, the basic adjustment isall right and it should be possible to adjust thefree play at the hand control. If there isn't anymovement, loosen the locknut (Figure 42) andslowly turn the adjuster screw counterclockwiseuntil there is movement in the operating lever.Turn the adjuster screw clockwise until you feelit touch the clutch operating rod, then back itout one full turn. Hold the screw to prevent itfrom turning further and tighten the locknut.Turn the cable adjuster at the hand control outuntil the free play is correct, as shown above.

BRAKE ADJUSTMENT

Front Brake (Drum Type)

The front brake cable should be adjusted sothat there is a minimum of brake lever move-ment required to actuate the brake, but it mustnot be so closely adjusted that the brake shoescontact the drum with the lever relaxed. Theprimary adjustment should be made with thecontrol lever adjuster. Because of normal brakewear, this adjustment will eventually be "usedup." It is then necessary to loosen the controllever adjuster and screw out the adjuster on thebrake backing plate (Figure 43) until the control

20 CHAPTER TWO

lever adjuster can be used once again for fineadjustment. After the backing plate adjuster hasbeen extended, be sure to tighten the locknut.

Adjustment of the connecting link betweenthe brake cams is described in Chapter Eight.

Rear Brake (Drum Type)

When the brake is fully applied the brakearm should be near perpendicular to the cable(Figure 44). Adjust the rear brake cable if nec-essary. After adjustment, release the brakepedal and spin the rear wheel to make sure theshoes do not contact the drum when the pedalis relaxed.

If the brake lever moves past vertical whenthe brake is applied, it is likely that the brakelining is worn and should be replaced. Referto Chapter Nine.

GREASE FITTINGS

Grease fittings on 750 and 850 Mark IImodels are located on the brake cam pivots (2cams on the drum type front brake. Figure 43),rear brake pedal pivot (Figure 45), and swingingarm pivot (Figure 46). On 850 Mark III modelsthere is a single grease fitting on the rear brakepedal pivot (Figure 47). These points should belubricated at the intervals shown in Table 1. Forfittings on brake components, one stroke of ahand-type grease gun is sufficient. Lubricationof the swinging arm pivot was described earlier.


AIR FILTER

The carburetor air filter element on 750 and850 Mark II models (Figure 48) should be re-placed every 5,000 miles or sooner if it appearsto be excessively clogged. The service life of thefilter can be extended by cleaning the element.Large particles can be dislodged by tapping thefilter on a work bench or other flat surface, andfine particles can be removed by blowing themout with low-pressure air applied to the insideof the element.

The carburetor air filter element on 850Mark III models is an oil-wetted type that canbe used almost indefinitely, provided it iscleaned and oiled periodically and the foam isnot torn or deteriorated. The element should beserviced every 3,000 miles, or more frequentlyif the motorcycle is operated in extremely dustyconditions. Unscrew the 3 bolts which hold thefilter cover in place (Figure 49) and slide theelement out of the air box, taking care not tosnag the foam on the carburetor drain plugs.Wash the filter thoroughly in clean gasoline,wring it out, and allow it to dry.

WARNINGBe extremely careful; clean the ele-ment out of doors and keep the gaso-line away from all flame and potential

22 CHAPTER TWO

sources of sparks. Pour the dirty gaso-line into a sealable container (notglass) and discard it in the trash.

After the cleaned element has dried, saturateit with clean engine oil, wring out the excess,and install the element in the air box.

WHEEL BEARINGS

The wheel bearings should be cleaned andrepacked with grease every 10,000 miles orafter submergence or prolonged running in deepwater. The correct service procedures are pre-sented in Chapters Eight and Nine.

PRIMARY CHAIN ADJUSTMENT

The primary chain on all models except the850 Mark III which is fitted with a hydraulictensioner, must be adjusted each time the pri-mary drive assembly is disturbed, and checkedevery 25,000 miles and adjusted if necessary.Total up-and-down movement of the chainshould be % in. (9.5mm). See Figure 50.1. Remove the oil fill/inspection cap from thetop center of the primary chaincase and checkthe movement of the chain with your finger.Rotate the crankshaft and chain with the kick-starter and check the movement in several loca-tions. At the tightest position, the movementshould be % in. If it is greater or less than this,proceed with the next steps.

2. Loosen the top gearbox bolt (do not turnthe captive nut on the left side) and the bottomnut (Figure 51).

3. Loosen the front adjuster nut several turns(Eigure 52). Tighten the rear adjuster nut untilthe chain is tight, then back it off until the move-ment of the chain is correct, while at the sametime tightening the front adjuster nut.

TUNE-UP

A complete tune-up should be performedevery 2,500 miles (650cc and 750cc models)


or 3,000 miles (85Occ Mark II and Mark IIImodels) of normal riding. More frequent tune-ups may be required if the motorcycle is riddenprimarily in stop-and-go traflBc.

The expendable ignition parts (spark plugs,points, and condenser) should be routinely re-placed at every other tune-up or when the pointcontacts or spark plug electrodes show signs oferosion. In addition, this is a good time to re-place the air filter element. Have the new partson hand before you begin.

Because different systems in an engine inter-act, the procedures should be done in thefollowing order:

a. Tighten cylinder head boltsb. Adjust valve clearancesc. Work on ignition systemd. Adjust carburetors

Cylinder Head Bolts

1. Raise or remove the seat.2. Shut off the fuel taps, disconnect the lines,and remove the fuel tank. On all original equip-ment Commando tanks, the front is mountedon 2 studs beneath the tank and held with self-

locking nuts. The rear mount on some modelsuses a rubber loop which passes beneath the topframe tube, while others are held in place witha metal cross bar.3. Tighten the nuts and bolts in the sequenceshown in Figure 53 to 20 ft.-lb. (2.75 mkg) forthe smaller (5/16 in.) bolts and 30 ft.-lb. (3.68mkg) for the larger (Vs in.) nuts and bolts. Thefuel tank can be left off at this time.

Valve Clearance Adjustment

Valve clearance adjustment must be madewith the engine cold. For standard 750cc en-gines and all 850cc engines, the inlet clearanceis 0.006 in. (0.15mm) and the exhaust clear-ance is 0.008 in. (0.2mm); for the 750cc Combatengine, the inlet clearance is 0.008 in. (0.2mm)and the exhaust clearance is 0.010 in. (0.25mm).1. Remove the rocker covers and unscrew thespark plugs from the cylinder head.2. Rotate the crankshaft with the kickstarteruntil the left inlet valve is completely open(Figure 54). Check the clearance of the rightinlet valve and rocker. When the clearance iscorrect, there will be a slight resistance on thefeeler gauge when it is inserted and withdrawn.3. To correct the clearance, back off the lock-nut and screw the adjuster out far enough toinsert the feeler gauge with no resistance. Screwin the adjuster until a slight resistance can befelt on the gauge. Hold the adjuster to preventit from turning further and tighten the locknut.Then, recheck the clearance to make sure theadjuster did not turn after the correct clearancewas achieved.

24 CHAPTER TWO

4. Rotate the crankshaft to open the rightintake valve completely and check and adjustthe clearance of the left inlet valve and rocker.Then, check and adjust the exhaust valves androckers in the same manner.

5. When all the clearances have been checkedand adjusted, install the rocker covers, makingsure the gaskets are aligned and in good con-dition. Reinstall the fuel tank.

Ignition System

Two similar contact breaker assemblies areused on Norton Commandos. They are de-scribed in Chapter Seven along with instructionsfor removal, inspection, and installation. Whenthe breaker assembly has been replaced, ordetermined to be serviceable, adjust as describedbelow.

1. Remove the spark plugs from the cylinderhead and rotate the crankshaft with the kick-starter to line up the mark on the point cam withthe lifter heel on one of the contacts (Figure 55).This is the maximum contact opening.

2. Measure the contact gap with a flat feelergauge (Figure 56). It should be 0.015 in.

(0.38mm). If it is not, loosen the breaker lock-screws (Figure 57) and move the plate in or outuntil the gap is correct. Tighten the lockscrewsand recheck the gap to make sure the plate didnot move when the screws were retightened.

3. Rotate the crankshaft to line up the cammark with the other lifter heel and adjust thiscontact set in the same manner as above.

4. Examine the spark plugs and compare theircondition to Figure 58. Their condition is anindication of engine condition and can warn ofdeveloping trouble. If the plugs are in goodcondition and can be reused, clean them with awire brush and blow out scale and deposits withcompressed air.


WARNINGHold the electrode end of the plugaway from you when blowing the scaleout with air.

5. Set the spark plug electrode gap at 0.028 in.(0.71mm) by bending the side electrode. Fornormal use, and for all models except the 750Combat, Champion N7Y spark plugs are rec-ommended; however, equivalent plugs of dif-ferent manufacture can be used if their heatrange corresponds to that of the N7Y. Plugsthat are too cold can cause hard starting. If theyare too hot, they can cause preignition whichmay result in engine damage.

Champion N6Y spark plugs are recommendedfor use in 750 Combat engines and for sustainedhigh-speed operation in other engines.

6. Screw the plugs into the cylinder head usingnew gaskets to ensure a good seal. Tighten themfirmly but not so tight that there is risk of dam-aging the threads in the head. Reconnect thehigh-tension leads.

NOTE: // the static timing procedurereferenced below is used, do not installthe spark plugs; it will be easier to ro-tate the crankshaft if there is no com-pression in the cylinders.

1, Refer to Ignition Timing, Chapter Seven,and accurately time the ignition. Two methodscan be used—static timing and dynamic timing(with the use of a strobe). The static method isaccurate enough for most situations, but strobetiming is essential for complete timing accuracyrequired for maximum performance. If statictiming is used, install the spark plugs and con-nect the high-tension leads as described aboveafter the timing has been set.

Carburetion

For stock engines, standard factory jetting isgood for most situations. Engine modificationsthat affect fiow or cylinder volume, as well asprolonged operation at extremes of altitude orhumidity, require changes in jetting and needle

26 CHAPTER TWO

SPARK PLUG CONDITION

NORMAL

• Identified by light tan or graydeposits on the firing tip.• Can be cleaned.

CARBON FOULED

• Identified by black, dry fluffy car-bon deposits on insulator tips, ex-posed shell surfaces and electrodes.• Caused by too cold a plug, weakignition, dirty air cleaner, too richa fuel mixture, or excessive idling.Can be cleaned.

FUSED SPOT DEPOSIT

* Identified by melted or spotty de-posits resembling bubbles or blisters.• Caused by sudden acceleration.Can be cleaned.

GAP BRIDGED

• Identified by deposit buildup clos-ing gap between electrodes.• Caused by oil or carbon fouling. Ifdeposits are not excessive, the plugcan be cleaned.

LEAD FOULED• Identified by dark gray, black,yellow, or tan deposits or a fusedglazed coating on the insulator tip.•Caused by highly leaded gasoline.Can be cleaned.

OVERHEATING

• Identified by a white or tight grayinsulator with small black or graybrown spots and with bluish-burntappearance of electrodes.* Caused by engine overheating,wrong type of fuel, loose spark plugs,too hot a plug, or incorrect ignitiontiming. Replace the plug.

OIL FOULED• Identified by wet black deposits onthe insulator shell bore electrodes.- Caused by excessive oil enteringcombustion chamber through wornrings and pistons, excessive clearancebetween valve guides and stems, orworn or loose bearings. Can becleaned. If engine is not repaired,use a hotter plug.

WORN

• Identified by severely eroded orworn electrodes.• Caused by normal wear. Shouldbe replaced.

PREIGNITION

• Identified by melted electrodes andpossibly blistered insulator. Metallicdeposits on insulator indicate enginedamage.• Caused by wrong type of fuel, in-correct ignition timing or advance, toohot a plug, burned valves, or engineoverheating. Replace the plug.


position. These are described in detail in Chap-ter Eleven, Performance Improvement, Thechecks and adjustments that follow assume thatjetting and needle position are correct.1. Loosen the throttle stop screws in both car-buretors until the throttle slides are completelyclosed (Figure 59).

2. Loosen the locknuts on the cable adjusters(Figure 60) and turn the adjusters either in orout until there is no perceptible end play in thecable sheaths when the slides are closed. Also,when the throttle grip is turned, the throttleslides must begin to lift together. When thethrottle slides are synchronized, hold the ad-justers to prevent them from turning andtighten the locknuts.

3. Start the engine, allow it to warm up forabout a minute, and turn the throttle so that itidles slightly faster than normal. Turn each ofthe throttle stop screws in slowly until they holdthe slides in this position with the throttlereleased.

4. With insulated pliers or screwdriver, pull thespark plug lead off one of the spark plugs.Screw in the pilot air screw (Figure 61) on thecarburetor on the opposite cylinder until theengine begins to falter (too lean). Then screw

28 CHAPTER TWO

it out—the engine will begin to run smoothlyagain—until the engine falters once again (toorich). Slowly screw it in until the engine beginsto run smoothly. Usually, the best position forthe screw is midway between the too-lean andthe too-rich idling positions (about 1 to P/^turns out).

5. Reconnect the spark plug lead on the oppo-site cylinder, disconnect the lead on the cylinderjust adjusted, and adjust the other cylinder inthe same manner.

6. With both pilot air screws adjusted and bothspark plug leads connected, the idle speed willprobably be too fast. In such case, carefullyunscrew each of the throttle stop screws equallyuntil the idle is acceptable. Recheck the endplay in the throttle cable sheaths. It shouldbe Vs in. (3mm) for each cable (Figure 62).

CHAPTER THREE

TROUBLESHOOTING

Diagnosing motorcycle ills is relatively simpleif you use orderly procedures and keep a fewbasic principles in mind.

Never assume anything. Don't overlook theobvious. If you are riding along and the bikesuddenly quits, check the easiest, most acces-sible problem spots first. Is there gasoline in thetank? Is the gas petcock in the ON or RESERVE

position? Has a spark plug wire fallen off?Check the ignition switch. Sometimes the weightof keys on a key ring may turn the ignitionoff suddenly.

If nothing obvious turns up in a cursory check,look a little further. Learning to recognize anddescribe symptoms will make repairs easier foryou or a mechanic at the shop. Describe prob-lems accurately and fully. Saying that "it won'trun" isn't the same as saying "it quit on the high-way at high speed and wouldn't start," or that"it sat in my garage for three months and thenwouldn't start."

Gather as many symptoms together as pos-sible to aid in diagnosis. Note whether the enginelost power gradually or all at once, what colorsmoke (if any) came from the exhausts, and soon. Remember that the more complicated a ma-chine is, the easier it is to troubleshoot becausesymptoms point to specific problems.

You don't need fancy equipment or compli-cated test gear to determine whether repairs can

be attempted at home. A few simple checkscould save a large repair bill and time lost whilethe bike sits in a dealer's service department. Onthe other hand, be realistic and don't attempt re-pairs beyond your abilities. Service departmentstend to charge heavily for putting together a dis-assembled engine that may have been abused.Some won't even take on such a job—so usecommon sense; don't get in over your head.

OPERATING REQUIREMENTS

An engine needs three basics to run properly:correct gas/air mixture, compression, and aspark at the right time. If one or more are miss-ing, the engine won't run. The electrical systemis the weakest link of the three. More problemsresult from electrical breakdowns than from anyother source. Keep that in mind before youbegin tampering with carburetor adjustmentsand the like.

If a bike has been sitting for any length oftime and refuses to start, check the battery fora charged condition first, and then look to thegasoline delivery system. This includes the tank,fuel petcocks, lines, and the carburetors. Rustmay have formed in the tank, obstructing fuelfiow. Gasoline deposits may have gummed upcarburetor jets and air passages. Gasoline tends

30 CHAPTER THREE

to lose its potency after standing for longperiods. Condensation may contaminate it withwater. Drain old gas and try starting with afresh tankful.

Compression, or the lack of it, usually entersthe picture only in the case of older machines.Worn or broken pistons, rings, and cylinderbores could prevent starting. Generally, a grad-ual power loss and harder and harder startingwill be readily apparent in this case.

STARTING DIFFICULTIES

Check gas flow first. Remove the gas cap andlook into the tank. If gas is present, pull off a fuelline at the carburetor and see if gas flows freely.If none comes out, the fuel tap may be shut off,blocked by rust or foreign matter, or the fuelline may be stopped up or kinked. If the carbu-retor is getting usable fuel, turn to the electricalsystem next.

Check that the battery is charged by turningon the lights or by beeping the horn. Refer toyour owner's manual for starting procedureswith a dead battery. Have the battery rechargedif necessary.

Pull off a spark plug cap, remove the sparkplug, and reconnect the cap. Lay the plug againstthe cylinder head so its base makes a good con-nection, and turn the engine over with the kick-starter. A fat, blue spark should jump across theelectrodes. If there is no spark, or only a weakone, there is electrical system trouble. Check fora defective plug by replacing it with a knowngood one. Don't assume a plug is good justbecause it's new.

Once the plug has been cleared of guilt, butthere's still no spark, start backtracking throughthe system. Tf the contact at the end of the sparkplug wire can be exposed, it can be held aboutV8 inch from the head while the engine is turnedover to check for a spark. Remember to hold thewire only by its insulation to avoid a nasty shock.Tf the plug wires are dirty, greasy, or wet, wrapa rag around them so you don't get shocked. Ifyou do feel a shock or see sparks along the wire,clean or replace the wire and/or its connections.

Tf there's no spark at the plug wire, look forloose connections at the coil and battery. Tf all

seems in order there, check next for oil or dirtycontact points. Clean points with electrical con-tact cleaner, or a strip of paper. On battery igni-tion models, with the ignition switch turned on,open and close the points manually with ascrewdriver.

No spark at the points with this test indicatesa failure in the ignition system. Refer to ChapterSeven (Ignition and Electrical Systems) forcheckout procedures for the entire system andindividual components. Refer to the same chap-ter for checking and setting ignition timing.

Note that spark plugs of the incorrect heatrange (too cold) may cause hard starting. Setgaps to specifications. Tf you have just riddenthrough a puddle or washed the bike and it won'tstart, dry off plugs and plug wires. Water mayhave entered the carburetor and fouled the fuelunder these conditions, but wet plugs and wiresare the more likely problem.

Tf a healthy spark occurs at the right time, andthere is adequate gas flow to the carburetor,check the carburetor itself at this time. Makesure all jets and air passages are clean, checkfloat level, and adjust if necessary. Shake thefloat to check for gasoline inside it, and replaceor repair as indicated. Check that the carburetorsare mounted snugly, and no air is leaking pastthe manifold. Check for a clogged air filter.

Compression may be checked in the field byturning the kickstarter by hand and noting thatan adequate resistance is felt, or by removing aspark plug and placing a finger over the plughole and feeling for pressure.

An accurate compression check gives a goodidea of the condition of the basic working partsof the engine. To perform this test, you need acompression gauge. The motor should be warm.

1. Remove the plug on the cylinder to be testedand clean out any dirt or grease.

2. Tnsert the tip of the gauge into the hole, mak-ing sure it is seated correctly.

3. Open the throttle all the way and make surethe chokes on the carburetors are open.

4. Crank the engine several times and recordthe highest pressure reading on the gauge. Runthe test on each of the cylinders. Refer to Chap-ter Four (Engine, Primary Drive, and Clutch)to interpret results.

TROUBLESHOOTING 31

POOR IDLING

Poor idling may be caused by incorrect carbu-retor adjustment, incorrect timing, or ignitionsystem defects. Check the gas cap vent for anobstruction.

MISFIRING

Misfiring can be caused by a weak spark ordirty plugs. Check for fuel contamination. Runthe machine at night or in a darkened garage tocheck for spark leaks along the plug wires andunder the spark plug cap. If misfiring occursonly at certain throttle settings, refer to the car-buretor chapter for the specific carburetor cir-cuits involved. Misfiring under heavy load, aswhen climbing hills or accelerating, is usuallycaused by bad spark plugs.

FLAT SPOTS

If the engine seems to die momentarily whenthe throttle is opened and then recovers, checkfor a dirty main jet in the carburetor, water inthe fuel, or an excessively lean mixture.

POWER LOSS

Poor condition of rings, pistons, or cylinderswill cause a lack of power and speed. Ignitiontiming should be checked.

OVERHEATING

If the engine seems to run too hot all the time,be sure you are not idling it for long periods.Air-cooled engines are not designed to operateat a standstill for any length of time. Heavy stopand go traffic is hard on a motorcycle engine.Spark plugs of the wrong heat range can bumpistons. An excessively lean gas mixture maycause overheating. Check ignition timing. Don'tride in too high a gear. Broken or wom rings maypermit compression gases to leak past them,heating heads and cylinders excessively. Checkoil level and use the proper grade lubricants.

BACKFIRING

Check that the timing is not advanced toofar. Check fuel for contamination.

ENGINE NOISES

Experience is needed to diagnose accuratelyin this area. Noises are hard to differentiate andharder yet to describe. Deep knocking noisesusually mean main bearing failure. A slappingnoise generally comes from loose pistons. Alight knocking noise during acceleration may bea bad connecting rod bearing. Pinging, whichsounds like marbles being shaken in a tin can,is caused by ignition advanced too far or gas-oline with too low an octane rating. Pingingshould be corrected immediately or damage topistons will result. Compression leaks at thehead-cylinder joint will sound like a rapid on-and-oflf squeal.

PISTON SEIZURE

Piston seizure is caused by incorrect pistonclearances when fitted, fitting rings with im-proper end gap, too thin an oil being used, incor-rect spark plug heat range, or incorrect ignitiontiming. Overheating from any cause may resultin seizure.

EXCESSIVE VIBRATION

Excessive vibration may be caused by loosemotor mounts, worn engine or transmissionbearings, loose wheels, worn swinging arm bush-ings, a generally poor running engine, broken orcracked frame, or one that has been damaged ina collision. See also Poor Handling.

CLUTCH SLIP OR DRAG

Clutch slip may be due to worn or glazedplates, incorrect adjustment, or too much oil inthe primary chaincase. A dragging clutch couldresult from damaged or bent plates, incorrectadjustment, uneven clutch spring pressure, or atight primary chain.

POOR HANDLING

Poor handling may be caused by impropertire pressures, a damaged frame or swingingarm, worn shocks or front forks, weak forksprings, a bent or broken steering stem, mis-aligned wheels, loose or missing spokes, womtires, bent handlebars, worn wheel bearing, ordragging brakes.

32 CHAPTER THREE

Tf shimmy, or "head shaking" occurs duringdeceleration, the alignment of the front tire onthe rim should be checked. Misalignment, par-ticularly for tires with a center groove, can causethe front wheel to "hunt" in a rapid oscillatingmotion when the weight is transferred forwardduring deceleration. To check for alignment,support the motorcycle so the front tire is clearof the ground. Place a short strip of maskingtape on the front fender, lined up with the centergroove in the tire. Now, spin the front wheeland sight along the tread, from the front of themotorcycle and visually line up the tire groovewith the tape on the fender. Tf the alignment iscorrect, the groove will not waver; however, ifthe tire is misaligned, the groove will waverback and forth.

This condition can often be corrected by de-flating the tire, soaping the seating bead, androtating the tire 90 degrees. After the tire hasbeen reinflated, recheck the alignment as before.Also, if the tire is rotated on the rim, the balanceof the wheel should be checked and correctedif necessary.

which have broken loose from the brake shoes.Glazed linings or glazed brake pads will causeloss of stopping power.

LIGHTING PROBLEMS

Bulbs which continuously burn out may becaused by excessive vibration, loose connectionsthat permit sudden current surges, poor batteryconnections, or installation of the wrong typebulb.

A dead battery or one which dischargesquickly may be caused by a faulty generator orrectifier. Check for loose or corroded terminals.Shorted battery cells or broken terminals willkeep a battery from charging. Low water levelwill decrease a battery's capacity. A battery leftuncharged after installation will sulphate, ren-dering it useless.

A majority of light and horn or other elec-trical accessory problems are caused by loose orcorroded ground connections. Check those first,and then substitute known good units for easiertroubleshooting.

BRAKE PROBLEMS

Sticking brakes may be caused by broken orweak return springs, improper cable or rodadjustment, or dry pivot and cam bushings.Grabbing brakes may be caused by greasy lin-ings which must be replaced. Brake grab mayalso be due to out-of-round drums or linings

TROUBLESHOOTING GUIDE

The following "quick reference" guide sum-marizes the troubleshooting process. Use it tooutline possible problem areas, then refer to thespecific chapter or section involved.

LOSS OF POWER

Cause Things to check

Poor Piston rings and cylindersCompression Head gaskets

Crankcase leaks

Overheated Lubricating oil supplyengine Clogged cooling fins

Ignition timing\ Slipping clutch

Carbon in combustion chamber


Improper Dirty air cleanermixture Restricted fuel flow

Gas cap vent holes

Miscellaneous Dragging brakesTight wheel bearingsDefective chainClogged exhaust system

TROUBLESHOOTING

STEERING PROBLEMS

Problenfi Things to check

Hard steering Tire pressureSteering stem headSteering head bearings

Pults to one side Unbalanced shock absorbersDrive chain adjustmentFront/rear wheel alignmentUnbalanced tires


Pulls to one side Defective swinging arm(contd.) Defective steering head

Shimmy Drive chain adjustmentLoose or missing spokesDeformed rimsWorn wheel bearingsWheel balance

BRAKE TROUBLES

Problem Things to check

Poor brakes Worn liningsBrake adjustmentOil or water on brake

liningsLoose linkage or cablesLow fluid level


Noisy brakes Worn or scratched liningScratched brake drumsDirt in brake housing

Unadjustable Worn liningsbrakes Worn drums

Worn brake cams

GEARSHIFTING DIFFICULTIES


Clutch AdjustmentFriction platesSteel plates—distortedOil quantity


Transmission Oil quantityOil gradeShift adjustmentShift quadrantShift forks

CHAPTER FOUR

ENGINE, PRIMARY DRIVE, AND CLUTCH

The Norton twin (Figure 1—Commando, andFigure 2—Atlas and G15) is a non-unit engine;that is, the engine and transmission do not sharea common case. As a result, major engine serv-ice, including a complete rebuild, can be car-ried out without disturbing the transmission.Upper end service (cylinder head, cylinders,pistons) can be accomplished without removingthe engine from the frame. Lower end servicerequires that the engine be removed from theframe which in turn requires that the primarydrive and clutch be removed.

CYLINDER HEAD

Cylinder head service is presented as a com-plete rebuild procedure so that the relationshipof the components can be better understood.Naturally, not all situations require that all partsbe replaced. However, every check, inspection,and measurement called for in this section shouldbe made each time the head is removed to ensurethat all parts are within specifications. If a wearcomponent, such as a valve guide, is satisfactory,its service procedure need not be carried out.

Removal

1. Raise or remove the seat. Disconnect thenegative battery lead at the fuse holder andremove the fuse (Figure 3).

2. Shut off the fuel taps, disconnect the lines,and remove the fuel tank. On all original equip-ment Commando tanks (Figure 4), the front ismounted on 2 studs beneath the tank and heldwith self-locking nuts. The rear mount on somemodels uses a rubber loop which passes beneaththe top frame tube, while others are held in placewith a metal cross bar.

3. Straighten the lock tabs on the finned head-pipe clamps (Figure 5) and unscrew the clamps.Unscrew the muflOier mounting nuts and the bal-ance pipe clamp nuts (Figures 6A and 6B) andremove each exhaust system as a unit.

4. Refer to Chapter Six and remove carburetors.

5. Carefully pull the caps off the spark plugs andunscrew them. Remove the entire coil assembly

ENGINE, PRIMARY DRIVE, AND CLUTCH 35

NORTON COMMANDOENGINE

36 CHAPTER FOUR

NORTON ATLASAND G15 ENGINE


COMMANDO FUEL TANKS

POLICE TYPE

INTERSTATEFIBERGLASS

ROADSTERFIBERGLASS

INTERSTATESTEEL

POLICE TYPE

FASTBACKFIBERGLASS

HIGH RIDER AND "SS"FIBERGLASS

38 CHAPTER FOUR

from the frame as a unit (Figure 7). Instead ofunplugging the leads and risking incorrect in-stallation later on, tie the assembly to the handle-bar with a piece of cord.

6. Unscrew the nuts which mount the head-steady to the frame (Figure 8). Unscrew the 3Allen screws (Figure 9) and remove the head-steady from the head.

On 850 Mark III models, loosen the nutwhich holds the spring trunion to the head and

disconnect the ends of the spring from thetrunion. Remove the spring from the framebracket.

7. Unscrew the bolts from the rocker feed pipe(Figure 10) and lift the pipe from the head.There's no need to disconnect the pipe from theengine lower end; however, it should be tied ortaped out of the way.


8. With the transmission in gear, rotate the rearwheel to bring the pistons to TDC. Unscrew thecylinder nuts and bolts in the pattern shownin Figure 11, beginning with No. 2. Remove the

front center bolt last. Lift the head, move thepushrods as far into the head as possible (Fig-ure 12), and remove it from the engine.

Disassembly

1. Remove the rocker covers and gaskets(Figure 13) and the spindle cover plates andgaskets (Figure 14).

2. Heat the cylinder head in an oven, at 300°F,for 30 minutes. Screw a slide hammer shaft(Norton tool No. 064298) into the end of therocker spindle and withdraw the rocker spindle.If a slide hammer is not available, an inexpen-sive substitute extractor tool like that shownin Figui 15 can be fabricated.

40 CHAPTER FOUR

Repeat the procedure for the remaining 3 shafts.Remove the rockers and the thrust washers.

3. Double nut the inlet rocker cover stud,Tighten the nuts securely against one another,and unscrew the stud with a wrench on the bot-tom nut (Figure 16). Compress each of the valvesprings in turn (Figure 17) and remove thekeepers from the valve stem (Figure 18) with a


CEI bolt

42 CHAPTER FOUR

small magnet or screwdriver. Release the com-presser and remove the valve, springs, collars,and the stem seals (inlet only). See Figures 19

and 20. Keep each valve assembly together andmark it for location in the head.

Inspection

1. Clean the carbon from the combustion cham-bers, exhaust ports, valves, and piston crowns

tNLET VALVE ASSEMBLY

.̂ ^^^^ ^^^z^^m

1. Keepers2. Collar3. Inner spring4. Outer spring5. Collar6. Insulator7. Sea!8. Valve


EXHAUST VALVE ASSEMBLY(Stem Seal not Used)

using either a special chemical carbon removeror a scraper made of soft metal, such as alumi-num. Then clean all of the parts in solvent anddry them.

NOTE: Don't remove the carbonridges around the tops of the cylindersor from the piston above the top com-pression ring.

2. Inspect the contact surface of each valve forburning (Figure 21). Minor roughness and pit-

ting can be removed by reseating the valve, butexcessive unevenness to the contact surface is anindication the valve is not serviceable. The con-tact surface of the valve may be ground on avalve grinding machine, but it's best to replacea burned or damaged valve with a new one.

Inspect the valve stems for wear and rough-ness and measure the vertical runout of the valveface as shown in Figure 22. The runout shouldnot exceed 0.001 in. (0.025mm).

44 CHAPTER FOUR

3. Measure the free length of the valve springs.The inner springs should be 1.482 in.(37.642mm) and the outer springs shouldbe 1.618 in. (41.097mm). Replace any springsthat are short.

4. Install each of the valves in its guide, in turn,and measure the clearance of the stem and theguide (Figure 23) in 2 axes to determine if theguide has worn oval. Tf the measurements aredifferent for the 2 axes, or if the clearance isgreater than 0.006 in. (0.152mm), the guideshould be replaced.

1. Valve 2. Dial indicator

5. Check the valve seats for excessive wear orpitting that can't be removed by lapping thevalve. In such cases, the seat must be recut. Also,the seat will have to be recut if the valve guideis replaced.

NOTE: Both the replacement of avalve guide and recutting a valve seatrequire special tools and skills. Thiswork should he entrusted to a Nortonservice shop or to a cylinder head re-building service.

6. Measure the bores of the rockers and therocker shafts. The difference (clearance) shouldbe no greater than 0.0020 in. (0.051mm).

Assembly

1. Lap each valve in its seat using a fine gradeof grinding compound and a hand lapping stick.Apply compound to the contact surface of the

valve and set the valve into the head. Wet thesuction cup on the end of the lapping stick andstick it to the head of the valve. Lap the valveto the seat by rotating the lapping stick in bothdirections (Figure 24). Every 5 to 10 seconds,rotate the valve head 180° in the seat, continuelapping until the contact surfaces of the valveand the seat are a uniform grey. Wash the headthoroughly with solvent, making sure no com-pound remains in the ports or the valve guides.2. Oil the valve stems and install the valves inthe head and reassemble the collars and springsin the order shown in Figures 19 and 20. All1971 and earlier engines must have heat insula-tors installed between the bottom spring collarand the head on the inlet valves, and all modelsmust have the insulators installed on the exhaustvalves.

NOTE: When guide replacement isrequired on early engines, late modelguides (Figure 25) should be installedto reduce oil consumption. Also,stem-to-guide seals must be installedon the inlet valve guides.

Also, on heads equipped with the type of guideshown in Figure 25, the stem and guide sealsmust be installed on the inlet valves (Figure 19).

Seal

Compress each valve assembly and install thesplit keepers in the top collars. Make sure thekeepers are firmly seated in the collar and thevalve stem groove.


3. Heat the cylinder head and start one of therocker shafts into its bore. On the exhaust rock-ers, the flat on the shaft (Figure 26) should faceforward, and on the inlet rockers the flat shouldface to the rear. Carefully tap the shaft in untilit protrudes about 1/16 in. (1.6mm) into thecase (Figure 27), Install a plain washer on theend of the shaft and set the rocker in place. Tapthe shaft in part way so that it engages the rockerand fits the spring washer between the end of therocker and the inside wall (Figure 28). Tap theshaft in until it passes through the spring washerand into the opposite boss in the head. If neces-sary, rotate the spindle using the slit in the outerend and line up the spindle as shown (Figure 29).Finally, tap the spindle the rest of the way inuntil the spindle is flush with or slightly beneaththe machined surface. Install the gaskets andplates in the order shown (Figure 30). Repeatthe procedure for each of the other rockers.

46 CHAPTER FOUR

Installation

1. Make certain the mating surfaces of the headand cylinders are clean and set the head gasketon top of the cylinders. If the position of thepistons has been disturbed, bring them to TDC byrotating the rear wheel with the transmission ingear. This is necessary to provide sufficient roomfor setting the head in place.

NOTE: It is recommended that thelatest head gasket with a 'Tlame Ring"be installed when the head is removedfor service. The new gasket is an im-provement over the copper and compo-sition fiber/ metal types. Before install-ing the gasket, clean the cylinder andhead mating surfaces with a non-petroleum base solvent such as lacquerthinner and install the gasket withoutgasket cement. Part numbers for the**Flame Ring" gasket are: 750 — No.063844; 850 — No. 065051.

2. Set the long intake pushrods—cups first—inthe inside bores and the shorter exhaust push-rods in the outside bores (Figure 31). Push therods into the head as far as they will go. Hold thehead in one hand and hold the pushrods in placewith the other. Position the head over the cylin-ders and let the pushrods down into their bores.


They will locate automatically on the camfollowers.

3. Before the head can be set in place on thecylinder, the pushrods must be lined up with therockers. Begin with the long rods and carefullyguide them into contact with the rockers, usinga small screwdriver or probe (Figure 32). Thendo the same with the shorter pushrods.

5. Install the bolts and washers on each side ofthe spark plug holes (Figure 34), Screw the longnuts onto the studs beneath the exhaust ports(Figure 35) and conventional nuts onto the studsbeneath the intake ports (Figure 36), None ofthese require washers. Next, screw the 2 nutswith washers onto the front studs (Figure 37).Tighten the nuts and bolts in the sequence shownin Figure 11 to 20 ft.-lb, (2,75 mkg) for thesmaller (5/16 in,) bolts and 30 ft.-lb, (3,68 mkg)for the larger (% in.) nuts and bolts.

4. Screw in the short bolt located at the centerof the front of the head (Figure 33). Make sureall the pushrod cups are engaged with the rock-ers and tighten this bolt to pull the head downonto the cylinders against the valve springpressure.

6. Adjust the valve clearances as described be-low and reassemble the remaining componentsin reverse order of their removal. The sparkplugs should be installed as soon as the valve

48 CHAPTER FOUR

clearances have been set to prevent nuts orwashers from falling into the cylinders.

Make sure the tubing to the rocker feed pipe isnot crimped or in contact with the head or head-steady. Check the wiring to the coil cluster tomake sure like colors are connected to likecolors. Finally, don't forget to reinstall the fusein the holder on the battery negative lead.

VALVE ADJUSTMENT

Clearance of rockers should be adjusted at2,500-3,000-mile intervals and each time cylin-der head or any part of valve train is removed

and installed. The clearances should be checkedand set with the engine cold. For the stand-ard 750 and 850 engines, the inlet clearanceis 0.006 in. (0.15mm) and the exhaust clear-ance is 0.008 in. (0.2mm); for the 750 Combatengine, the inlet clearance is 0.008 in., (0.2mm)and the exhaust clearance is 0.010 in. (0.25mm).

1. Remove the rocker covers and unscrew thespark plugs from the head.

2. Rotate the crankshaft using the kickstarteruntil the left inlet valve is completely open(Figure 38). Check the clearance of the rightinlet valve and rocker. When the clearance iscorrect, there will be a slight resistance on thefeeler gauge when it is inserted and withdrawn.

3. To correct the clearance, back off the locknutand screw the adjuster out far enough to insertthe gauge with no resistance. Screw the adjusterin until a slight resistance can be felt in thegauge. Hold the adjuster to prevent it from turn-ing further and tighten the locknut. Recheck theclearance to make sure the adjuster didn't turnafter the correct clearance was achieved.

4. Rotate the crankshaft to open the right intakevalve completely and check and adjust the clear-ance of the left valve and rocker. Then, checkand adjust the exhaust valves and rockers in thesame manner.


CYLINDERS AND PISTONS

Cylinder wear should be checked each timethe head is removed or if such symptoms asexcessive oil consumption, performance degra-dation, or piston slap indicate the possibility ofthe cylinders being worn beyond service limits.

Removal

1. Remove cylinder head as described earlier.

NOTE: On 750 engines, it is not nec-essary to remove the head from thecylinder; they can be removed togetheras an assembly after the spark plugshave been removed, the crankshaft isrotated to bring the pistons to BDC,and the cylinder base nuts are un-screwed,

2. On 850 engines, unscrew the 4 thru-bolts(Figure 39) and 5 nuts (Figures 40A and 40B).

On 750 engines, unscrew 9 nuts around the baseof the cylinders. The nuts must be unscrewedprogressively; it's essential to lift the cylinderassembly so that the nuts will not jam against thefin above them. Remove all washers (there arenone on the front center stud) before lifting thecylinder assembly off the pistons. Prevent therods from falling forward or backward againstthe crankcase as the cylinder is lifted free.

3. Stuff a clean shop rag into the top of thecrankcase to prevent small parts and dirt fromfalling into the crankcase. A wooden blockmade from soft wood (like the one shown inFigures 41 and 42) will protect the connectingrods, crankcase opening, and piston skirts.

NOTE: On 850 engines, mark the pis-tons, **right'* and *'left" and **front** sothat they may be installed in the loca-tions and direction from which theywere removed.

50 CHAPTER FOUR

4. Remove the circlips from the wrist pin boresin the pistons (Figure 43) and press the pins outwith a drift or a small socket on an extension.The piston must be held securely so that noneof the force that is required to push out the pinis applied to the connecting rod. It's advisable tohave someone help you hold the piston. Underno circumstances should you hammer on thedrift; if the pin can't be moved, warm the piston

for several minutes by wrapping a rag, heatedin hot water, around it.

Inspection

1. Remove the rings from the pistons by spread-ing the ring ends with your thumbs and liftingthe rings up evenly (Figure 44). Carefully cleanthe carbon from the piston crown with a chem-ical remover or with a soft scraper. Try not toremove or damage the carbon ridge around thecircumference of the piston above the top ring.If the pistons, rings, and cylinders are found tobe dimensionally correct and can be reused, re-moval of the carbon ring from the tops of pistonsor the carbon ridges from the tops of cylinderswill promote excessive oil consumption.


CAUTIONThe rail portions of the oil scraper canbe very sharp. Be careful when hand-ling them to avoid cut fingers.

Clean the ring grooves in the pistons usingeither a groove scraper or a piece of old ring.Then clean the piston in solvent and dry itthoroughly.

2. Measure the cylinder bores at the pointsshown in Figure 45 in 2 axes—in line with thewrist pins and at 90° to the pins. If taper or out-of-round are greater than 0.005 in. (0,127nini),the cylinders must be bored to the next oversizeand new pistons installed. Bore sizes are shownin Table 1.

NOTE: The new pistons should be ob-tained before the cylinders are boredso that pistons can be measured; slight

Bmanufacturing tolerances must be tak-en into account to determine the actualbore size and the working clearance.Piston-to-cylinder clearance should be0.0035-0.0040 inch (0.089-0J0mm).

If a cylinder gauge or inside micrometer isnot available, cylinder wear can be checked byplacing a compression ring in the cylinder at thelocations shown in Figure 45 and measuring thering gap with a flat feeler gauge. The ring mustbe positioned squarely into the cylinder. Thiscan be accomplished by pushing it into placewith the head of a piston (Figure 46). This meth-od is not as accurate as the first and if any doubtexists about the serviceability of a cylinder, theunit should be checked by a dealer.

Table 1 BORE SIZES

Engine

750CC

850CC

Piston

Standard:-|- 0.010 in. oversize+ 0.020 in. oversize-f 0.030 in. oversize+ 0.040 in. oversize

Standard:+ 0.010 in. oversize+ 0.020 in. oversize+0.040 in. oversize+0.060 in. oversize

Bore Size

2.875 in. (73.025mm)2.885 in. (73.279mm)2.895 in. (73.477mm)2.905 in. (73.787mm)2.915 in. (74.041mm)

3.032 in. (77.013mm)3.042 in. (77.267mm)3.052 in. (77.521mm)3.072 in. (77.970mm)3.092 in. (78.477mm)

52 CHAPTER FOUR

Installation

1. Make certain the threads of the crankcasestuds are clean and apply a light coat of greaseto them. Carefully coat the cylinder mountingflange with Loctite "Plastic Gasket" or gasketcement.

NOTE: Omit the base gasket (earlymodels) to reduce oil seepage at thecylinder flange. Normal flexing of thecrankcase causes the gasket to extrudeafter several thousand miles, promot-ing bothersome seepage.

2. Install one circlip in each piston. Make surethe clip is installed with the sharp edge facingout (Figure 47) so the clip will lock in the groove.Heat the pistons in hot water.3. Lightly oil the wrist pin bores in the connect-ing rods and pistons, set the pistons in place onthe rods, and push the pins in, taking care tosupport the pistons so there is no side loading onthe rods. Then fit the remaining circlips, againmaking sure the sharp edge of each clip facesoutward.

CAUTIONThe piston stamped RH miist be in-stalled on the right connecting rod andthe one stamped LH must be installedon the left. Also, the EX stamp on eachpiston must face forward, toward theexhaust ports.

4. Rotate the crankshaft to bring the pistonsinto contact with the wooden block and installthe rings—first the oil scraper, then the secondand top compression rings (Figure 48). Rotate

COthe rings in the grooves to position the end gapsas shown in Figure 49. When aligning the scrap-er ring, make sure the gaps in the rail and theexpander are staggered and that the ends of theexpander do not overlap (Figure 50).5. Lightly oil the pistons and install the ringcompressors (Figure 51). The compressorsshould be snug enough to compress the ringsbut not so tight that they won't slip easily downand off the rings when the cylinders are installed.

6. Set the cylinder block in place on top of thepistons and push it quickly and evenly down over


Top ringgap t

FRONT

Oil ring

gaps(see Figure 50)

Second ring

gap

the pistons and rings. Remove the ring com-pressors and the wooden block and lower thecylinder block part way down over the studs sothe washers and nuts can be installed.

7. Tighten the nuts in the sequence and to thetorque values indicated in Figure 52.8. Install the cylinder head as described earlier.

54 CHAPTER FOUR

750CC 850CC

240 in.-lb./20 ft.-Ib. (2.75 mkg)360 in.-lb./30 ft.-Ib. (4.15 mkg)300 in.'lb./25 ft.-Ib. (3.75 mkg)

BREAK-IN

Following cylinder servicing (boring, honing,new rings, etc.) and major lower end work, theengine should be broken in just as though itwere new. The performance and service life ofthe engine depend greatly on a careful andsensible break-in.

For the first 500 miles no more than one-thirdthrottle should be used and speed should bevaried as much as possible within the one-thirdthrottle limit. Prolonged, steady running at onespeed, no matter how modeate, is to be avoided,as is hard acceleration.

Following the 500-mile service (below) in-creasingly more throttle can be used but fullthrottle should not be used until the motorcyclehas covered at least 1,000 miles and then itshould be limited to short bursts until 1,500miles have been logged.

The mono-grade oils recommended for break-in and normal use (Table 2) provide a superiorbedding pattern for rings and cylinders than domulti-grade oils. As a result, piston ring andcylinder bore life are greatly increased. How-ever, the factory has found that complete bed-ding does not occur until about 1,200 miles and

Table 2 RECOMMENDED MONO-GRADEBREAK-IN OILS

CastrolGPor HD40

Kendall Racing 40

Shell—Aero Shell No. 80, 40W

Torco Racing 40

Valvoline Racing 40

during this period oil consumption will be higherthan normal. It is therefore important to fre-quently check and correct the oil level. At notime, during break-in or later, should the oillevel be allowed to drop below the "L" mark onthe dipstick; if the oil level is low, the oil willbecome overheated resulting in insufficientlubrication and increased wear.

500-Mile Service

It is essential that the oil and filter be changedand the sump filter cleaned after the first 500miles. In addition, it is a good idea to changethe oil and filter and clean the sump filter at thecompletion of break-in (about 1,500 miles) toensure that all of the particles produced during


break-in are removed from the lubrication sys-tem. The small added expense may be cbnsid-ered a smart investment that will pay off inincreased engine life.

PRIMARY DRIVE AND CLUTCH

The entire primary drive assembly must beremoved from the motorcycle before the crank-case can be removed.

Disassembly

1. On 750 and 850 Mark II models, remove thenuts and washers which hold the left footrestand rear brake pedal assembly in place(Figure 53). Pull the unit off the studs and allowit to hang on the brake cable. On Mark IIImodels it is not necessary to remove the gearselector pedal; simply remove the left footrest.

2. Place a drip pan beneath the primary chain-case. The pan should be as long as the chaincaseto prevent oil from being spilled when the coveris removed. On 750 and 850 Mark IT models,unscrew the nut in the center of the cover(Figure 54). On 850 Mark III models, unscrewthe 11 screws located around the outer edge ofthe case. Pull the cover off the alignment dowelsand away from the chaincase. Remove any oilthat remains in the bottom of the chaincase.

NOTE: // the entire primary driveassembly is to be removed, proceed insequence with the next step and re-move the alternator rotor and stator.However, if only the clutch is beingserviced, there's no need to disturb thealternator. Skip Steps 3 through 7.

3. On 750 and 850 Mark II models, reinstallthe footrest/brake pedal assembly and screw thenuts on finger-tight. On all models, depress thebrake pedal to lock the rear wheel and preventthe clutch from turning, unscrew the rotor nut(Figure 55), and remove the large washer.

4. Unplug the stator leads (Figure 56) and care-fully pull the leads and the rubber grommet outof the primary chaincase (Figure 57). On 850Mark III models, remove the shifter cross shaft(Figure 58) by pulling it straight out to the left.

56 FOUR

NOTE: For most operations the statorlead need not be removed from thecase. Make sure, however, that thestator is not allowed to hang from theelectrical lead,

5. Unscrew the stator mounting nuts, removethe washers, and pull the stator off the studs(Figure 59). On 750 and 850 Mark II models,remove the spacers from the studs (Figure 60).

6. Pull the rotor off the crankshaft. If necessary,the rotor may be broken loose from the shaft byapplying pressure with 2 tire irons (Figure 61).Remove the key, spacer, and shims from the


shaft. Set the rotor into the stator, wrap theassembly in clean newspaper and set it aside.On 850 Mark III models, straighten the locktabs on the nuts which attach the inner frame,unscrew the nuts, and pull the frame off thestuds (Figure 62), Remove the inner washer,bushing, starter gear, and starter intermediatedrive assembly (Figure 63). Remove the sprag

58 CHAPTER FOUR

i/

clutch and bushing (Figure 64) and inner race(Figure 65) from the crankshaft. Unscrew thenuts from the tensioner cover plate (Figure 66)and remove it. Note the location of the smallernut. Hold the top and bottom tensioner pads inplace to prevent them from jumping out of thetensioner body and pull the tensioner off thestuds (Figure 67).7. Unscrew the clutch adjuster locknut and theadjuster screw from the center of the diaphragm(Figure 68).

8. Install the diaphragm compressor (Nortontool No. 060999) on the diaphragm (Figure 69).

The tool bolt must be threaded into the dia-phragm at least 6 full turns. Hold the compressorarms to prevent them from turning and turn thecompressor nut clockwise until the spring ro-tates freely in the clutch housing.9. Use the tip of a small screwdriver to lift theend of the diaphragm retaining clip out of itsgroove (Figure 70) and peel it out of the grooveall around the circumference. Remove the tooland the diaphragm together. If the diaphragmis in good condition and is to be reused, it's notnecessary to remove the tool. If the tool must be

60 CHAPTER FOUR


removed, however, hold the bolt with onewrench and turn the compressor nut counter-clockwise until the diaphragm is completely re-laxed before unscrewing the bolt.

CAUTIONAny attempt to remove the diaphragmcircUp without use of the compressortool would be extremely hazardousand at the very least could cause severedamage to the clip and the clutch body,Installation of the diaphragm and clipwithout the use of the compressor isvirtually impossible, if the tool cannotbe purchased or borrowed^ the jobshould be entrusted to a Norton serviceshop,

10. If only the clutch is being serviced, removethe plates one at a time using a small magnet todraw them out of the body and off the hub(Figure 71). Then refer to the inspection andassembly sections which follow. If the entireprimary drive is to be removed, however, leavethe plates installed and proceed with the stepswhich follow.

11. On 750 and 850 Mark II models, with thefootrest/brake pedal assembly installed as de-scribed above, depress the brake pedal (allmodels) to lock the rear wheel and prevent theclutch hub from turning. Straighten the lock-washer tabs and unscrew and remove the nut,washer, and tab washer (Figure 72).12. Install the sprocket puller (Norton toolNo. 064297) on the engine sprocket (Figure 73).Screw the puller bolts in at least 8-10 turns andthen turn in the center bolt tightly against theend of the crankshaft. Rap the sprocket sharplywith a steel drift and hammer to jar the sprocket

loose from the taper on the crankshaft. Removethe puller from the sprocket.13. On 750 and 850 Mark II models, once againremove the footrest/brake pedal assembly and

62 CHAPTER FOUR

pull off the engine sprocket, chain, and clutchtogether (Figure 74). Note the location andarrangement of the spacer and shims on the maintransmission shaft and remove them and setthem out of the way. These pieces locate theclutch sprocket in alignment with the enginesprocket and should not be substituted oreliminated during assembly.

14. On 750 and 850 Mark II models, straightenthe tab washers on the chaincase mounting bolts(Figure 75), unscrew them, and pull the chain-case away from the engine and transmission.Screw the bottom 2 bolts back into the crankcaseto prevent oil from dripping out. On 850 MarkIII models, disconnect the electrical lead to thestarter (Figure 76), unscrew the starter mountingscrews (Figure 77), and pull the starter out of theprimary case. Unscrew the nut from the centerof the inside case half and pull the case off thelong crankcase studs.

Inspection

1. Inspect the O-rings, rubber cover seal, andalternator cable grommet for wear or deteriora-tion and replace any of these pieces that aredefective.


2. Inspect the rollers of the primary chain andthe sprocket teeth for wear and damage. Nor-mally, these components will last for manythousands of miles; however, incorrect chaintension or extremely dirty oil can cause under-cutting of the sprocket teeth (Figure 78) andaccelerated wear on the chain rollers.

Damaged sprocket'teeth

Worn sprocketteeth

Normal sprocket teeth

of the sprockets should be checked andcorrected if necessary by adding or re-moving shims from the transmissionmain shaft, behind the clutch wheel.The outer row of teeth on eachsprocket must be the same distancefrom the mating edge of the primarychaincase (Figure 80).

3. After thoroughly washing and drying theclutch plates, inspect the splines for wear(Figure 79) and check the contact surfaces of allthe plates for signs of burning, galling, and deepgrooving. All questionable plates should bereplaced.

4. Check the splines on the clutch hu'b and inthe drum for signs of wear and damage andreplace as necessary.

NOTE: // one or both of the primarysprockets are replaced, the alignment

5. Inspect the chaincase and outer cover forcracks and fractures and for damage to thesealing surfaces. Repairs to either of these cast-ings should be attempted only by a specialistexperienced in the repair of non-ferrous preci-sion castings.

The following inspection points apply only tothe 850 Mark III:

6. Inspect the teeth of the starter gears for chip-ping and excessive wear. Minor burnishing ofcontact areas is acceptable but deep scarring or

< i

Crankshaftsprocket 7

Distance Amust equaldistance B

CHAPTER FOUR

chipped teeth are reason for replacement. In-spect the rollers and cage in the crankshaftstarter gear for wear and damage and replacethe bearing assembly if necessary (Figure 81).

7. Check the sprag clutch (Figure 82) for wearand damage. Counter-rotate the inner and outercages. The rollers should extend and retractwith no eJBfort or binding.

8. Inspect the gear selector cross-over assemblyfor damaged teeth and splines (Figure 83). Ifthe gear teeth are damaged, resulting in shiftingdifficulties, the gearset can be rotated 180° toeliminate the damaged teeth from the mesh.

9. Check the rubber contact shoes of the chaintensioner (Figure 84) for deeply worn grooves.These pieces will wear normally and they shouldbe replaced before the primary chain wearsthrough the rubber and comes in contact withthe metal.

Assembly

1. Install the engine sprocket key in its recessin the crankshaft (Figure 85). Make sure it seatscompletely and that there is no roughness alongthe flat which would prevent it from enteringthe keyway in the sprocket.


2. Lightly coat both sides of the crankcase/chaincase gasket with Loctite "Plastic Gasket"or gasket cement and set it in place on the crank-case (Figure 86). Place the flat washer and shim(if one was removed) on the end of the chaincasecenter stud (Figure 87).

3. Set the chaincase in position, making surethe seal in the case does not snag on the trans-mission main shaft (Figure 88). On 750 and 850Mark IT models, install the 3 bolts with tabwashers which hold the chaincase to the crank-case, tighten them securely, and bend the tabsover to lock them in place. On 850 Mark IIImodels, screw in and tighten the chaincasecenter nut.4. Install the clutch spacer (recess toward thetransmission—Figure 89) on the main shaft, fol-lowed by the shim or shims (Figure 90). Assem-ble the sprocket and the chain (Figure 91). Set

ooO

66 CHAPTER FOUR

them in position on their shaft and rotate themto line up the keyway in the crankshaft sprocketwith the key in the shaft and push the sprocketsand chain all the way on together,

5. Line up the splines in the clutch center hubwith the splines on the transmission main shaftand push it on. Install the washer and nut. If thewasher is a tab type, engage 2 of the tabs withthe holes in the hub. Install the footrest/brakelever assembly as before, depress the brakepedal, and tighten the center nut to 70 ft.-lb.(9.68 mkg). Bend the tab washer over to en-gage 2 flats on the nut.

6. Install the clutch plates in the carrier, begin-ning with a friction plate (splines on inner diam-eter — Figure 92), followed by a steel plate(splines on outer diameter—Figure 93), alter-nating plates until all 9 are in place. Then installthe iron pressure plate (Figure 94).

7. Reinstall the assembled compressor tool anddiaphragm as before, making sure the com-pressor nut is backed off to permit the plate torelax until the center bolt has been threaded intothe diaphragm at least 6 full turns. Then turn thecompressor nut clockwise until the diaphragmis flat and set the diaphragm into the clutch asfar as it will go. Start one end of the diaphragmclip into the groove in the clutch body and pressit into place until it is fully seated all the wayaround the clutch. Turn the compressor nutcounterclockwise until the diaphragm is relaxedand unscrew the tool's center bolt.

8. Remove the inspection cover from the rightside of the transmission and check to see thatthe clutch operating lever is correctly positioned(Figure 95), If it is not, pull it up into place sothe recess in the lever engages the roller.


9. Install the clutch adjuster screw and locknut(Figure 96). Turn the hand control cable ad-juster all the way in (Figure 97) and turn the ad-juster screw in until the diaphragm just beginsto lift or move outward. Then turn the screw outone full turn, hold it to prevent it from turningfurther, and tighten the locknut securely.

10. On 850 Mark III models, install the innerrace for the sprag clutch in the crankshaftsprocket with the notched side of the race facingout (Figure 98). Set the sprag clutch in thesprocket with the flanged side facing in. Tiltthe clutch outward from the top and introducethe bottom edge first. Install the bushing, startergear (with the castellated side of the hub facingout), and the washer. Refer to the disassemblyinstructions and install the chain tensioner andthe starter intermediate drive assembly. Makecertain the recess in the thrust washer covers thecirclip (Figure 99). Move the large idler gear upinto engagement with the small idler gear beforeattempting to fit the intermediate drive assembly.

68 CHAPTER FOUR

Install the inner frame on the studs, screw onand tighten the nuts, and bend the tab washersover against one Hat on each nut.11. On 750 and 850 Mark II models, install theshims and spacer (recess outward) on the crank-shaft (Figure 100) and set the rotor key inits recess.

12. Inspect the rotor for any panicles it mayhave attracted and clean it if necessary. Installit on the shaft, lined up with the key and withthe timing marks facing out (Figure 101). Installthe washer and nut, apply the rear brake, andtighten the nut to 70-80 ft.-lb. (9.68-11.06 mkg).


13. Thread the stator leads through the chain-case and press the grommet into the hole, mak-ing sure it is fully seated. Set the stator spacerson their studs and install the stator with the leadon the outside positioned at about 5 o'clock(Figure 102). Install the washers and nuts andtighten them to 15 ft.-lb. (2.07 mkg). On 750and 850 Mark II models, check the air gap be-tween the rotor and stator with a flat feeler gauge(Figure 103). Ideally, it should be even all theway around but not less than 0.008-0.010 in.(0.203-0.254mm) at any one point. If the gap isless than this, it may be possible to realign thestator by loosening the nuts, pushing the statorin the direction of the smallest gap, and re-tightening the nuts to the torque specified. Ifthis does not work, one or more of the studs isprobably bent. It may then be possible to cor-rect the gap by very carefully realigning thestuds. Should this fail, the studs should be re-placed with new ones that are known to bestraight. When the air gap is correct, reconnectthe stator leads.

On 850 Mark III modeis, set the stator inplace and push it on evenly so the stator bodyfits inside the machined stud bosses. Install thewashers and nuts and tighten them progressivelyin a criss-cross pattern to draw the stator onevenly all the way around. The air gap onMark III models is self-adjusting.

Install the gear selector cross-over shaft mak-ing sure its splines correctly engage the splinesin the connector sleeve (Figure 104). Install the

\

starter with the electrical post facing up andscrew in and tighten the mounting screws. Re-connect the electrical lead.14. On 750 and 850 Mark II models, install therubber sealing ring in the groove in the innerchaincase with the joint seal at the top (Fig-ure 105). Set the outer cover in place, carefullyaligning it with the dowels. Push the cover onevenly and install the mounting bolt and washer.Install the level plug, timing inspection plug,and clutch adjuster plug, with 0-rings.

On 850 Mark III models, lightly coat bothsurfaces of the gasket with gasket cement andset the gasket in place over the hollow alignmentdowels. Hold the cover up to the primary caseand position the gear selector pedal in its oper-ating position and push the cover on, movingthe pedal slightly if necessary so that its gear canengage the gear on the cross-over shaft. Screw in

70 CHAPTER FOUR

and tighten the case screws in a criss-cross pat-tern. Note the location of the long screw whichpasses through the case and screws into thestarter motor (Figure 106).

15. For Mark II models, refer to Chapter Two,Primary Chain Adjustment, and adjust the pri-mary chain so that there is total up-and-downmovement of the chain of % in. (9.5mm) at thetightest point.

16. Pour 7 ounces (200cc) of an oil recom-mended in Chapter Two into the chaincase andinstall the fill plug with its O-ring.

17. Install the footrest/brake pedal assembly.

ENGINE LOWER END

Service to the engine lower end requires thatthe crankcase assembly be removed from themotorcycle. The complete primary drive assem-bly must first be removed and it's advisable thatthe head, cylinders, and pistons be removedalso; they'll have to come off anyway and thetask of removing them with the engine installedin the frame is considerably easier. In addition,the decrease in engine weight at the point atwhich the crankcase is lifted from the frame willbe greatly appreciated.

Because of differences in work habits andavailability or absence of certain tools such as asuitable large bench vise, or an elevated work-stand, no hard-and-fast rule is set down here forthe point at which the crankcase assembly shouldbe removed from the motorcycle. It may be re-moved at Step 8 as described, or you may electto wait until Step 13 has been completed.

The lower end service procedure is presentedas a complete rebuild. To service and repairmajor components related to the lower end butnot requiring its removal and disassembly, dis-assemble the engine up to the point at which theaffected part can be reached and then reassemblefrom that point on beginning with the appro-priate step in the Assembly section; just besure that a subsequent component has not beenaffected by the failure or deterioration of acomponent located earlier in the disassemblyprocedure.

Removal and Disassembly

1. Refer to earlier sections in this chapter andremove the seat, fuel tank, coil assembly, ex-haust system, cylinder head, cylinders, pistons,and primary drive assembly.

2. Unscrew the tachometer cable collar (Fig-ure 107) and pull the cable out of the crankcase.On 750 and 850 Mark II models, unscrew thegear indicator bolt (Figure 108) and remove theindicator. Loosen the bolt in the gear selectorpedal (Figure 109) and pull the pedal off theshaft. On all models, unscrew the rocker feedpipe bolt (Figure 110) and remove the washersfrom each side of the union.


3. Place a drip pan beneath the engine. On 850models, loosen the clamp on the crankcasebreather hose (Figure 111) and pull the hose offthe nipple and direct it so that residual oil willdrain into the pan. On 750 models, removethe 2 bolts which hold the breather to the crank-case, pull the breather away and remove thegasket (Figure 112). Unscrew the bolt from theoil pipe junction (Figure 113) and remove itand the gasket.4. Loosen the crankcase filter located beneaththe engine (Figure 114) on 850 models, and

72 CHAPTER FOUR

CRANKCASE - 750 ENGINE

1. Crankcase2. Crankcase dowel3. Crankcase dowel4. Camshaft bushing5. Main bearing6. Main bearing oil seal7. Main bearing shim8. Cylinder stud, front9. Cylinder stud stepped

10. Cylinder stud, front11. Cylinder stud washer12. Cylinder stud washer13. Cylinder stud nut14. Cylinder stud nut15. Cylinder stud nut16. Oil pump stud

17. Oil pump stud nut18. Grub screw-oil stop19. Junction block dowel20. Crankcase bolt, long21. Crankcase bolt nut22. Crankcase bolt, short23. Crankcase bolt washer24. Crankcase bolt nut25. Crankcase stud stop, "front26. Crankcase stud washer27. Crankcase stud nut28. Crankcase stud stop, rear29. Crankcase stud washer30. Crankcase stud nut31. Crankcase screw, T.S. to D.S.

at sump

32. Magnetic sump plug33. Sump plug washer34. Gear tachometer35. Screw36. 0-ring37. Housing38. Tachometer housing gasket39. Breather tube40. Sump filter body41. Filter washer42. Filter gauze43. Strainer44. Bolt45. Filter body washer46. Tab washer


unscrew the drain plug on all models and allowthe crankcase to drain.5. Unscrew the left nut from the front mount(Figure 115), line up one of the flats on the rightend bolt head so it will clear the timing case(Figure 116), and tap it about halfway out. Peelback the left cover (Figure 117) and remove thespacer, end cap, and shims. Unscrew the nutsfrom the engine mounting bolts (Figure 118)and remove the bolts. Remove the completefront mount (Figure 119).

74 CHAPTER FOUR

6. Remove the bottom- and center-rear enginebolts (Figure 120). When removing the bottombolt it will be necessary to lift up on the crank-case so the bolt will clear the frame.7. On models equipped with a sump filter, liftthe front of the engine and place a long drift orsocket extension beneath it so that it is sup-ported on the frame rails (Ffgure 121). Removethe filter and allow the remaining oil to drain.

8. Unscrew the nut from the top rear enginebolt (Figure 120), lift up on the engine, and pullthe bolt out. Lift the crankcase assembly out ofthe frame, taking care not to damage it onthe mounts.

9. Remove the bottom front crankcase bolt(Figure 122). Mount the crankcase assembly ina bench vise fitted with protective jaw covers.


The timing side of the crankcase should face youand the vise should be tight enough to hold thecrankcase firmly (Figure 123).

10. Remove the contact breaker cover, unscrewthe breaker cam bolt and remove it along withthe 2 washers (Figure 124), Screw the end of theslide hammer (Norton tool No. 064298) intothe end of the cam at least 6 full turns, pull theslide sharply to free the cam from the taper onthe shaft (Figure 125), and remove it. Unscrewthe 12 screws from the timing cover (Fig-ure 126). Carefully tap the cover loose with asoft mallet and remove it from the crankcase.Feed the electrical leads through the hole inthe case, one at a time.

11. Unscrew the oil pump nuts (Figure 127) androtate the pump drive gear bolt (Figure 128)clockwise with a wrench to draw the pump awayfrom the case. Place 2 blocks of wood over thetop opening in the crankcase, pass a drift throughthe wrist pin holes in the connecting rods, andturn the oil pump worm nut clockwise to bringthe drift in contact with the blocks (Figure 129).Unscrew the worm nut (left-hand thread) usingeven pressure on the wrench. Remove the wormgear from the shaft.

12. Unscrew the camshaft nut (Figure 130),again using even pressure on the wrench. Loosenthe nuts on the timing chain tensioner (Fig-ure 131) and remove the sprockets, idle gear,

76 CHAPTER FOUR

and chain together with the aid of a puller(Figure 132).13. Install the extractor (Norton tool No.ET.2003) on the crankshaft pinion gear withthe tool jaws lined up with the flats on the washer(Figure 133). Hold the tool to prevent it fromrotating and turn the puller bolt clockwise toremove the pinion. Remove the key from theshaft and the washer. With a small magnet,remove the lipped seal disc (Figure 134). It'snot necessary to remove the chain tensionerunless the contact shoe is deeply worn and mustbe replaced.

In such case, the tensioner should be replacedwith the latest type which has a rubber facing onthe slipper surface, resulting in quieter opera-tion and reduced wear of the chain sideplates.


14. Remove the crankcase from the vise. Un-screw the nuts, bolts, and screws which hold thecrankcase halves together (Figure 135). Sepa-rate the cases with a soft wood dowel appliedagainst the cylinder recess in the timing side(Figure 136). Remove the engine breather discand spring (750 engines prior to No. 200000)from the drive-side cam bushing as the casesare separated.

78 CHAPTER FOUR

15. Remove the camshaft and thrust washerfrom the timing case (Figure 137). On enginesfrom No. 200000 to 300000, remove the flatthrust washer.

Thrust washer

16. Fit a suitably-sized length of tubing overthe end of the crankshaft (Figure 138). Withassistance, stand the tube on end on a workbench and tap along the mating surface of thecrankcase with a block of wood and a hammerto drive the case off the bearing (Figure 139).

NOTE: This is not necessary on en-gines with a roller bearing on the tim-ing side of the crankshaft (after Num-ber 200000).

If necessary, the crankcase may be heatedwith a propane torch in the area of the bearing.

17. Unscrew the nuts from one of the con-necting rods and remove the rod and end capfrom the crank. Mark both the cap and rod forposition (right or left) and direction (front). SeeFigure 140. Then remove the other rod assemblyand mark it appropriately. Under no circum-stances should the rods and caps be inter-changed, switched from one side to the other,or reversed (along a vertical axis) when theyare reinstalled.

18. Scribe a "T" on the timing side of the fly-wheel so that it may be installed in the sameposition from which it was removed. Unscrewthe nuts from the timing side (Figure 141) andbreak the crank halves loose from the flywheelwith a soft mallet or a hammer and soft drift.The crank should be parted over a drip pan tocatch the oil remaining in the assembly.

Inspection

1. Thoroughly clean all the parts in solvent anddry them. Pay particular attention to the crankassembly which will likely have an accumulationof sludge in the crank halves and the flywheel.Blow out the oilways in the crank with air pres-sure. Do the same with oil feed and fllter lines.

2. Inspect the crank journals for scoring andgalling. Minor roughness may be removed withflne emery cloth. Measure the journals on thehorizontal and vertical axes (Figure 142) to

ENGINE, PRIMARY DRIVE, AND CLUTCH

check for out-of-roundness. If the differencebetween the 2 axes on either journai is greaterthan 0.0015 in. (0.038mm), the journals mustbe ground to the next undersize with a 0.090in. (2.28mm) face radius (Figure 143 andTable 3) and new bearings installed.

New bearings are available in finished sizesof —0.010, —0.020, —0.030, and —0.040 tocorrespond to the specified regrind dimensions.

3. If the connecting rod journals do not have tobe reground, inspect the connecting rod bear-ings for scoring and galling. Minor roughnessmay be removed with fine emery cloth but noattempt should be made to salvage a bearing thatis deeply scored or galled. If crank journal wearis very slight, consideration may be given toreplacing the bearings with a new set of thesame size. However, if any doubt exists, it'spreferable to have the journals reground tothe next undersize and appropriate bearingsinstalled.

4. Rotate the main bearings by hand, either inthe cases or on the crankshaft, and check forroughness and radial play. The bearings should

80 CHAPTER FOUR

CRANK JOURNAL MEASUREMENTS

1,7405 in.1.7400 in.diameter

1.7305 in.1.7300 in.diameter

.090 in. radiusIMPORTANT

1.7205 in.1.7200 in.diameter

FIRST REGRINDGrind the crankpin to1.7405 in./1.7400 in. diameterwith .090 in. face radius

Stamp—.010 in. here

SECOND REGRINDGrind the crankpin to1.7305 in./1.7300 in. diameterwith .090 in. face radius


THiRD REGRINDGrind the crankpin to1.7205 in./1.7200 in. diameterwith .090 in. face radius


Table 3 JOURNAL REGRIND SIZES

Regrind Dimension (Crankpin dia.) Size Stamp

FirstSecondThird

1.7405-1.7400 in. (44.175-44.162mm)1.7305-1.7300 in. (43.921-43.908mm)1.7205-1.7200 in. (43.667-43.654mm)

.010.020.030


turn smoothly and exhibit no appreciable play.If a bearing is to be replaced, it's first necessaryto heat the case in the area of the bearing andthen dislodge the bearing either with a soft driftapplied to the bearing inner race (timing sideball-type bearings) or by rapping the casesharply on a piece of soft wood.

The cast must also be heated when a bearingis being installed, and the bearing should fitcompletely into the bore with no effort.

CAUTIONWhen heating the case during removalor installation of a bearing, do notbring the flame in contact with anypart of the bearing; even a brief ex-posure to the flame can destroy thecase hardening on the bearing.

On engines equipped with roller main bear-ings, inner races should be removed from crank-shaft with a puller (Norton tool No. 063970).See Figure 144.

6. Inspect the seals in the timing cover for dam-age or deterioration (Figure 145). Oil in thecontact breaker cavity is a good indication thatthe contact breaker seal is failing and should bereplaced. The seal can be removed by prying itout with a screwdriver* be careful not to damagethe case. Press a new seal evenly into the sealbore with the open side facing out (Figure 146),using Norton tool No. 064292.

5. Check the cam bushings, journals, and lobesfor wear and damage. Minor roughness on tjielobes may be removed with fine emery cloth.

The crankshaft seal is held in the case with acirclip. To remove the seal, first remove the cir-clip (Figure 147). Then carefully pry the seal outof the case. Install a new seal squarely in thebore, with the open side facing in (Figure 148),and install the circlip with its sharp edge facingout so it will lock in the groove.7. Check the end-play of the oil pump gears. Ifthe gears have begun to wear into the oil pump

82 CHAPTER FOUR

body covers, in and out movement of the drivegear will be apparent. Wearing in of the gearsreduces the efficiency of the pump but the condi-tion can be corrected by honing the sides of thepump body to compensate for the wear. Removethe 4 screws from the pump and remove the rearcover. Use a small drift to drive the shaft out otthe keyed gear (Figure 149). Disassemble thepump and clean and dry the parts thoroughly.Beginning with the feed side of the pump (nar-row gears), hone the face of the pump on a pieceof fine emery cloth laid on a surface plate or apiece of glass. Periodically check your work byassembling the pump and checking its rotationalmovement. Sufficient material has been removedwhen a slight resistance to rotation can be felt.

Hone the scavenging side in the same manner,checking the resistance with only the scavenginggears installed in the pump. When both sideshave been corrected, carefully wash and dry allof the parts and assemble the entire pump. Squirtoil into the feed hole (Figure 150) and turn thepump drive gear several revolutions until thepump turns freely.

8. On 850 Mark III models, clean and checkthe oil anti-return valve in the outer cover(Figure 151), The valve piston should movefreely in its bore with a slight spring resistance.

Assembly and Installation

1. Polish the connecting rod journals with fineemery tape. Wash and dry the crank halves.Blow out the oilways with compressed air. Is-stall 2 short studs in the inner holes in the fly-wheel. Set the drive side crank half over thestuds on the drive side of the flywheel (oppositeof side marked with "T") and install the lockplate and 2 short nuts. Set the timing side crank


\

half in place on the opposite ends of the studsand install the lock plate and 2 short nuts. Installthe remaining 4 studs from the drive side withthe long studs in the outer holes and screwon the nuts—short nuts to short studs and longnuts to long studs. Tighten the nuts, beginningwith the inner ones and working diagonally,to 25 ft.-lb. (3.45 mkg). Bend the tabs over onthe inner nuts and stake the others with a centerpunch to keep them from backing off. Screw theoilway plug into the timing side crank cheek andtighten it securely.

2. Oil the bearing shells and fit them to theconnecting rods and end caps (Figure 152). Notethat the drilled shell half is fitted to the rod andthe plain one to the cap. Oil the journals andinstall the right side rod and cap on the rightjournal (timing side) with the oil hole in the rodto the outside. The front of the rod, as markedduring disassembly, should be on the right sideof the journal viewing the crank from the rightend (Figure 153). Install the original bolts andnew nuts and tighten them to 25 ft.-lb. (3.45mkg). Install the left-hand rod and cap in thesame manner, with the oil hole in the rod tothe outside.

.Forward

Connectingrod

84 CHAPTER FOUR

NOTE: The self-locking nuts must bereplaced each time the connecting rodassembly is parted. Also, if a new con-necting rod is being installed, do notuse the non-locking nuts that hold therod assembly together in the package.Discard these and use the self-lockingnuts that are also included.

3. Oil the main bearings and the crankshaft andset the timing side of the crankcase in place overthe right end of the crankshaft (Figure 154) andpress it down into place. Make sure the con-necting rods line up with the cylinder spigotcutaway in the case. Hold the rods in this posi-tion and prevent them from turning by slippinga heavy rubber band or piece of inner tube overthem and pushing it down against the flywheel.

NOTE: Main bearings should be re-placed with bearing No. 064118, avail-able through Norton parts dealers. SeeSources list in Chapter Eleven.

4. Dab some grease on the flat side of the cam-shaft thrust washer and set it in place on thebushing (Figure 155). On engines from No.200000 to 300000, make sure that the flat thrustwasher is located between the bushing and thechamfered washer, and that the tab on thewasher engages in the hole beneath the bushing.

5. In the drive-side case half, install the rotarydisc and spring on engines prior to No. 200000.Lightly oil the end of the camshaft and install itin the bushing. (On engines prior to No. 200000,make sure the camshaft engages with the dogson the disc.)

6. Coat the mating surface of the timing-sidecase half with Loctite *Tlastic Gasket" or gasketcement and oil the timing end of the camshaftand the drive side main bearing. Hold the cam-shaft in place in the drive side case and set thecase in position on the crankshaft (Figure 156).Push the case into place, making sure the cam-shaft lines up with the thrust washer and thebushing and that the connecting rods are cen-tered in the cylinder spigot recesses. If resistanceis felt just before the case halves contact, checkthe tachometer drive to make sure it engageswith the gear on the camshaft. Tap the crankcasehalves together all around the mating line witha soft mallet. Check the camshaft to make sureit has some end-play.

7. Install the screws, studs, washer, nuts, andshort front bolts in the crankcase. Omit the bot-tom bolt at this point so that the crankcase maybe clamped in a vise. Tighten the nuts and screwsevenly in a crosswise pattern.

8. Clamp the crankcase in a vise as for disas-sembly and install the oil seal disc (lip out) andthe washer on the timing side of the crankshaft.Set the key in the crankshaft recess and installthe crankshaft gear with the timing marks out-ward. Rotate the crankshaft so the timing markis at the top and journals are at TDC (Figure 157).


9. Assemble camshaft sprocket, gear sprocket,and chain with the marks on the sprockets lo-cated 10 rollers apart (Figure 158). Line up themarked space on the intermediate gear with the

86 CHAPTER FOUR

marked tooth on the crankshaft gear and installthe assembled sprockets and chain (Figure 159).10. Install the cam chain tensioner as shown inFigure 160—thin plate inside with the long enddown, the tensioner, and the thick plate on theoutside with the long end up. Install the washersand nuts and adjust the tensioner so that themaximum up and down movement of the chainis 3/16 in. (4.8mm) at the tightest point. Rotatethe crankshaft, checking the chain movementevery several plates until you are certain thatthe adjustment is correct at the tightest position.Tighten tensioner nuts to 15 ft.-lb. (2.07 mkg).

11. Screw on the oil pump drive gear (left-handthread) and the camshaft nut (right-hand thread).Lock the crankshaft as described in the disas-sembly section, this time rotating the crankshaftcounterclockwise (from the right end) until thedrift is stopped against the blocks. Then tightenboth the drive gear and the camshaft nut.

12. Prime the oil pump by turning the drivegear and squirting oil into the pump through thefeed port (Figure 161). Install the oil pump onthe mounting studs (with a gasket if one wasremoved during disassembly) after making surethe studs are tight. Screw on the nuts (nowashers) and tighten them to 10-12 ft.-lb. (1.38-1.66 mkg). Install a new oil seal (part No.NMT272) on the pump outlet (Figure 162).Omit any shims that may have been removedduring disassembly, provided a gasket is used.Check the tightness of the drive gear.

13. Install the timing cover gasket over thedowels in the crankcase. Screw a seal protector(Norton tool No. 061359) into the end of thecamshaft and lightly oil it (Figure 163). If the


tool is not available, wrap the end of the shaftwith a piece of transparent mending tape andshape it into a cone. The tool or the tape arerequired to protect the contact breaker oil sealfrom damage when the timing cover is installed.14. Remove the crankcase from the vise, tilt itonto its left side (drive side) and squirt severalounces of fresh engine oil into the flywheelthrough the right end of the crank (Figure 164).Allow a couple of minutes for the oil to run intothe journals and reciamp the crankcase assemblyin the vise.

15. Insert the contact breaker electrical leadsthrough the hole in the timing case and set thecover in place. Install the timing cover screwsand tighten them in the sequence shown inFigure 165. Unscrew the seal protector tool ifused, or remove the tape from the end of thecamshaft.

16. Lightly lubricate the automatic advancemechanism with oil. Make sure the cam taper isclean and dry and set the unit in position(Figure 166).

17. Install the contact breaker assembly withthe yellow lead to the rear (Figure 167). Line upthe plate so that the pillar bolts are in the centerof their slots and tighten them.

18. Remove the crankcase from the vise andinstall the bottom front bolt, the drain plug, andthe oil filter on 850 models.

88 CHAPTER FOUR

12

19. Set the crankcase in the frame, between therear mounting plates, and install the top andcenter rear bolts (Figure 168). Lift up on theengine and install the bottom bolt from the rightside. Install the washers and screw the nuts onfinger-tight.

20. Set the complete front mount in place asshown in Figure 169 and install the bottom bolt.Pivot the mount up and install the top bolt.

Refer to Chapter Ten and assemble the shims,caps, spacers, and covers. Install the right-handset first and lift up the front of the crankcase toalign the mount with the frame tab. Push the boltinto the mount, lining up one of the fiats on thebolt head to clear the timing case. Before the boltreaches the other bushing, install the left-handset and then push the bolt the rest of the waythrough.

Fit the lips of the outer covers over the caps,install the washer and nut, and tighten it to 25ft.-lb. (3.45 mkg). Tighten the nuts on the Ys in.studs to 25-30 ft.-lb. (3.45-4.15 mkg) and thoseon the 5/16 in. boh to 15 ft.-lb. (2.07 mkg).21. The remaining components should be as-sembled and installed in reverse order of dis-assembly. Refer to the appropriate sections andchapters to ensure that your work is correct.Following engine installation, the engine shouldreceive a major service including fresh oil, igni-tion timing and adjustment, carburetor adjust-ment, primary and secondary chain adjustment,clutch adjustment, and brake adjustment.

C H A P T E R F I V E

TRANSMISSION

The 4-speed Norton transmission (Figure 1)is not unitized with the engine and can thereforebe completely dismantled and serviced withoutdismantling the engine. However, removal ofthe gearset from the transmission housing, re-moval of the entire transmission from the motor-cycle, or removal and replacement of thecountershaft sprocket requires disassembly ofthe primary drive.

There are few situations requiring removal ofthe transmission housing from the motorcycle(such as repair to a crack or fracture, renewal ofthe drain plug threads, etc.). Even the bearingsin the main housing can be removed with anexpanding type bearing puller with the housingin place.

Beginning in 1975, with the Mark III ElectricStart, the gear selector mechanism was rede-signed to provide left-foot shifting with a 1-down, 3-up change pattern. This change wasmade to accommodate international agreementsfor standardization of motorcycle controls.

The transmission service procedures in thischapter are arranged by subassembly (outercover, inner cover, gasket, and selectors). It'snot necessary to totally dismantle the transmis-sion to correct many unsatisfactory conditionsthat may arise through normal use and wear.For instance, replacement of a worn kickstarter

pawl requires no disassembly beyond that re-quired for the inner cover. Be certain, however,that an unsatisfactory condition that's found inan early disassembly step has not affected com-ponents covered in later steps. If the possibilityexists that subsequent components may havebeen damaged by a known failed component orassembly, continue to disassemble and inspectthe transmission until you're confident that allunserviceable parts and conditions have beencorrected.

OUTER COVER

The outer cover houses the clutch operatingmechanism, the gear selector stop plate, and thestarter return spring.

Removal

1. Place a drip pan beneath the transmissionand remove the drain plug. Remove the fusefrom the holder on the negative battery lead(Figure 2).

2. Unscrew and remove the bolt from the kick-starter lever (Figure 3) and pull the kickstarterlever off the shaft. It may be necessary to strikethe bottom of the foot lever with a mallet tobreak the kickstarter loose from the shaft.

TRANSMISSION 91

92 CHAPTER FIVE

Right footrest

3. Unscrew the nuts and bolt from the rightfootrest (Figure 4) and remove it. Note the loca-tion of the red ground wire (Figure 5) so it canbe installed in the same manner later.

4. On right-foot selector models, remove thesetscrew and washer from the gear selector indi-cator (Figure 6) and remove the indicator butnot the gear selector pedal.

5. Remove the cover inspection cap and gasket(Figure 7) and disconnect the end of the clutchcable from the clutch fork (Figure 8).6. Remove the 5 screws which hold the cover inplace (Figure 9). Place the drip pan beneath theouter cover. Tap gently around the edge of theouter cover with a soft mallet and pull the cover

TRANSMISSION 93

away from the transmission with the shift leverand off the starter and gear selector shafts.7. On right-foot selector models, unscrew andremove the bolt from the gear selector pedal andremove the pedal from the shaft. Remove thepawl assembly and the ratchet plate from thecover (Figure 10). On left-foot selector models,remove the pawl assembly and ratchet from theinner cover.

A. Pawl assembly

Inspection

1. Thoroughly clean and dry all parts. Checkthe 0-rings and gaskets for damage and deteri-oration and replace them if necessary.

2. Check the teeth on the pawl (Figure 11) andthe ratchet plate for wear. They should be evenand sharp to ensure accurate engagement.

3. Install the kickstarter lever on its shaft anddepress it part way to check the resiliency of thespring. The resistance of the spring should befirm and even, and when the lever is relaxed, thespring should hold it firmly against the stop.

4. Install the ratchet and pawl assembly in theouter cover (Figure 12) and fit the gear selectorpedal onto its shaft. Alternately lift and depressthe pedal and check the resiliency of the pawlspring by observing the movement of the pawl.With the pedal relaxed, the pawl should be cen-tered with the arms of the spring not quitetouching the ends of the pawl (Figure 13). Asthe pedal is lifted or depressed, the pawl shouldimmediately begin to move toward engagement.

94 CHAPTER FIVE

TRANSMISSION 95

5. On 850 Mark III models, check the condi-tion of the splines on the pawl assembly shaftfor rust or damage. Light rust can be removedwith a wire brush, after which the splines shouldbe lightly coated with oil to inhibit further rust.Check the protector boot on the coupling sleevefor damage or deterioration and replace it ifnecessary.6. Check the mating surfaces of the inner andouter covers for roughness and burrs. Minordamage can be removed by carefully dressingthe surface with fine emery cloth. Remove anybit of gasket that may have remained attachedwhen the gasket was removed.

Installation

1. Install new O-rings (Figure 14) in the startershaft and selector shaft bores in the outer cover,and in the groove on the ratchet shaft.

2. Put the spring washer and the return springon the selector shaft. Make sure the ends of thespring straddle the arm on the pawl assembly(Figure 15). Install the shaft and pawl assemblyin the cover. Install the stop plate, making sure

the ends of the return spring straddle the tangon the inside of the stop plate (Figure 16). Thentighten the stop plate screws.3. Install the pawl spring (Figure 17). Thespring arm which has 2 bends must be on thebottom. Check to see that there is a very slight

96 CHAPTER FIVE

clearance (0.010 in. minimum) between thespring arms and the ends of the pawl (Figure 18).4. Coat the mating surfaces of the inner andouter covers with gasket cement and set thegasket in place on the inner cover.

5. Line up the outer cover with the inner cover,making sure the coil of the pawl spring goesover the ratchet shaft. Be careful not to disturb

the position of the pawl spring. Otherwise, itwill rotate the pawl and disturb its alignmentwith the ratchet plate. Carefully push the outercover all the way on. If there is hard resistancebefore the cover contacts the gasket, pull thecover away and check the alignment of the pawlspring and the pawl.

On left-foot selector models, also check thealignment of the splines on the pawl assemblyshaft with the splines of the collar that connectsit to the thru-shaft.

TRANSMISSION 97

7. Install and tighten the transmission drainplug and fill the transmission with 0.9 pts.—U.S.; 0.75 pts. Imperial—U.K.; 420cc of oil.Connect the clutch cable to the fork and adjustthe cable's free play. Install the inspection coverand gasket and check the cover mating surfaceand drain plug for leaks.6. When the cover is in position, install the 5screws and tighten them securely. Install thekickstarter lever and gear selector pedal on theirshafts and check their operation. Slowly rotatethe rear wheel and operate the gear selectorpedal to engage each of the gears. If the opera-tion is satisfactory, install the gear selectorindicator.

INNER COVER

The inner cover functions as the right half ofthe transmission case in addition to housing theclutch operating mechanism and part of the gearselector mechanism.

Removal

1. Remove outer cover as described previously.

2. Unscrew the bolt which holds the clutch lever(Figure 19) in the clutch operating body andremove the lever.

3. Mark the location of the clutch operatingbody with 2 punch or scribe marks (Figure 20)and unscrew the lock ring from the inner cover.Remove the clutch operating body and the ball(figure 21).

4. Shift the transmission into fourth gear bycarefully prying the quadrant up (Figure 22)while slowly rotating the rear wheel. Withassistance, apply the rear brake and unscrewthe transmission main shaft nut (Figure 23),Release the brake, slowly rotate the wheel, andshift the transmission back into neutral by care-fully prying the quadrant down.5. It is not necessary to remove the kickstarterassembly from the inner cover. However, if thekickstarter pawl is suspected of being damagedor worn (see Inspection), carefully pry thethe inboard tang of the kickstarter spring off

98 CHAPTER FTVE

the post (Figure 24). Disengage the outboardtang from the hole in the starter shaft andremove the spring.

6. Unscrew 7 nuts which mount the inner coverto the transmission (Figure 25).

7. Tap gently around the edge of the inner coverwith a soft mallet and pull the cover away fromthe transmission.

8. Withdraw the clutch operating rod from thetransmission main shaft (Figure 26) and pullthe starter shaft out of the cover (Figure 27).

Inspection

1. Thoroughly clean and dry all parts. Checkthe gasket for damage or deterioration and re-place it if necessary.

TRANSMISSION 99

3. Rotate the main shaft bearing (Figure 29) byhand and feel for roughness and radial play. Anymovement other than smooth rotation should bebarely perceptible. If the bearing is found to beunserviceable, warm the case and dislodge thebearing by tapping the cover on a block of softwood. Press in a new bearing while the case isstill warm, until the bearing is fully seated in thebore (Figure 30).

2. Check the kickstarter pawl (Figure 28) forwear. Also make sure it moves freely in its pivotand that the spring and plunger will hold it open.

4. Check the starter shaft and layshaft bushings(Figure 31) for signs of wear and galling. Lightlyoil the starter shaft bushing and install the shaftin the cover. Rotate the shaft and check to seethat it turns smoothly and that there is onlyslightly perceptible radial movement. Check thelayshaft bushing in the same manner, while in-stalled in the end of the starter shaft, then whileinstalled on the end of the layshaft (Figure 32).Check the bushing for the ratchet plate.

100 CHAPTER FTVE

5. Examine the cover casting for cracks andfractures. If any are found, the casting must bereplaced or repaired by a specialist familiar withrepairing precision aluminum castings.

Installation

1. Install the kickstarter shaft and bushing inthe case. Compress the pawl and rotate the shaftso that the pawl is held down by the stop(Figure 33). Fit the starter return spring on theshaft with the outboard tang in the hole in theshaft and the inboard tang over the post in thecover (Figure 34).

2. Fit the layshaft bushing into the end of thestarter shaft.

3. Coat the mating surfaces of the transmissioncase and the inner cover with gasket cement andset the gasket in place on the transmission.

4. Check to make sure the main shaft and lay-shaft are completely seated in transmission case.

5. Line up the inner cover with the main shaftand the layshaft and push it into place. Screwon the 7 mounting nuts and tighten them in thepattern shown to 12 ft.-lb. (1.66 mkg).See Figure 35.6. Shift the transmission into fourth gear bylevering the ratchet plate carefully upward whileslowly rotating the rear wheel. With assistance,apply the rear brake and tighten the transmissionmain shaft nut to 70 ft.-lb. (9.7 mkg). Thenshift the transmission back into neutral.

TRANSMISSION 101

7. Assemble the clutch operating body, ball,and lock ring and install it in the cover. Line upthe mark in the body with the mark in the cover(Figure 36) and tighten the lock ring until itsnotches line up with the marks. When the clutchoperating body is correctly aligned, the cable andlever are in alignment so that a straight pull isapplied to the lever (Figure 37).

8. Install the clutch lever, roller, bushing, andbolt in the end of the clutch body and screw onand tighten the locknut (Figure 38).9. Install the ratchet plate in the cover (Fig-ure 39), making sure the peg in the plate engagesthe hole in the quadrant roller. Put the O-ringon the ratchet shaft and seat it in the groove.

102 CHAPTER FTVE

10. Install the outer cover referring to the pro-cedure presented earlier.

GEARSET AND HOUSING

The main transmission housing contains thegearset, shifting forks, camplate, and quadrant.Removal of the gearset from the housing re-quires that the inner and outer cover assembliesbe removed and the primary drive and clutch bedisassembled (see Chapter Four).

Removal

1. Remove the shims, spacer, and circlip fromthe left end of the main shaft (Figure 40).

NOTE: Reuse of this circlip is notrecommended.

2. Remove the first gearset from the right endsof the main shaft and layshaft, along with thelayshaft first gear bushing (Figure 41),

3. Unscrew the selector spindle (Figure 42)from the case and pull it out of the forks. Re-move the forks from the gearset.

4. Pull the main shaft, with second and thirdgears (Figure 43), out of the case. Fourth gearwill be held in the case by the countershaftsprocket and bearing. Remove the layshaft andgears. It may be necessary to warm the case inthe area of the countershaft left-end bearing andremove the bearing with the shaft.

5. Unscrew the setscrew from the countershaftnut lock plate (Figure 44) and remove the plate.Install the left footrest and brake lever assemblv

and tighten the nuts finger-tight. Apply the rearbrake and unscrew the left-hand thread counter-shaft nut (Figure 45). Disconnect the rear chainand remove the sprocket from the shaft. Tap

TRANSMISSION 103

7. Unscrew the 2 bolts which hold the camplateand quadrant in the case (Figure 48). Removecamplate and quadrant and the 2 O-ring seals.

the fourth sleeve gear (Figure 46) carefully intothe case with a soft mallet.6. Unscrew the detent bolt from the bottom ofthe case and remove the camplate detent plungerand spring (Figure 47).

8. Remove the spacer from the countershaftseal (Figure 49) and carefully pry the seal outof the case.9. Warm the case in the area of the main shaftleft-end bearing and remove the bearing with anexpanding type bearing puller. If a puller is notavailable, the bearing may be removed by tap-ping very gently on a soft drift inserted throughthe left side of the case. If the bearing does notrelease easily, don't force it; excessive pressure

104 CHAPTER FIVE

on the bearing will damage it. In such case, it'sbetter to inspect the bearing installed in the caseand remove it only if it's found to be defective.

Inspection

1. Thoroughly clean and dry all the componentsas well as the inside of the transmission case.

2. Rotate the bearings by hand and feel forroughness and radial and axial play between theinner and outer races. The bearings should turnsmoothly and play should be barely perceptible.

3. Check both shafts for wear and damage to thesplines, threads, and bearing surfaces.

4. Check each gear for chipped or worn teeth.Some bright burnishings of the contact area ofthe gear teeth is normal, but deep scores or chipsindicate an unsatisfactory gear. It's recom-mended that both gears in a set (layshaft andmain shaft) be replaced if one of the gears isunsatisfactory; while wear or damage on themating gear may not be as apparent, its condi-tion could be such that it won't permit a newgear to wear in correctly.

5. Check the engagement dogs (Figure 50) forexcessive rounding or chipping. Check internallysplined gears for wear and damage to the splines.

6. Examine the gear bushings for signs of wearor damage and check their serviceability byinstalling them on the shaft with their gears andattempt to rock the gear from side to side. Anyappreciable rocking movement is an indicationthat the bushing should be replaced. Check thecondition of the camplate and quadrant bushings

in a similar manner, by installing the bushingsand camplate and quadrant in the case andchecking for rocking movement.

7. Check each selector fork in the groove of itsappropriate gear by rotating the gear and feelingfor roughness or sticking (Figure 51). Minorroughness on the fork or in the groove can beremoved with fine emery cloth but excessivewear or damage is an indication that the fork orgear or both should be replaced.

8. Check the condition of the teeth in the quad-rant and on the camplate for roughness, chip-ping, or wear (Figure 52). Check the camplatetracks and the detent profile (Figure 53) and thedetent plunger (Figure 54) for wear and galling.

TRANSMISSION 105

Assembly

1. Warm the transmission case in the area of theleft-end bearings and press them into the caseuntil they contact shoulders in bearing bores.

2. Allow the case to cool; then line up thecountershaft seal squarely with the bore, withthe lip seal facing inward, and press the seal inevenly until it is flush with the case (Figure 55).

3. Assemble the detent plunger, spring, andacorn bolt and install them in the bottom of thecase. Turn the bolt in only a couple of turns.

4. Install the quadrant in the case. Make surethe bushing is in place and that the O-ring seal isinstalled in the outside end of the boss (Fig-ure 56) and is covered by the washer. Tightenthe bolt securely.

CHAPTER FIVE

5. Line up the upper edge of the quadrant armwith the top front case stud (Figure 57) and in-stall the camplate with its teeth engaged withthe teeth on the quadrant with the camplate posi-tioned as shown (Figure 58). The notched edgeof the camplate must face the left side of thetransmission and the plunger should index thebottom notch. Make sure the camplate bushingis in place in the boss in the case and install theO-ring seal, washer, and bolt. Tighten the cam-plate bolt securely, then tighten the acorn detentbolt in the bottom of the case.

brake, and tighten the nut securely. Install thelockwasher and screw (Figure 60).

6. Install the main shaft fourth gear in the caseand install the spacer on the shaft on the sealside, inside the seal bore (Figure 59). Fit thecountershaft sprocket to the shaft and reconnectthe rear chain. Screw on the countershaftsprocket nut (left-hand thread), apply the rear

7. Fit main shaft into fourth gear (Figure 61).Install a new circlip on the clutch end of the

main shaft (Figure 40). Make sure it is com-pletely seated in the groove.

8. Assemble the layshaft, third and fourthgears, and the third gear bushing, as shown inFigure 62. The dogs on third gear must faceoutward, and the flat side of fourth gear must

TRANSMISSION 107

face third gear. Install the layshaft in the bearingin the case (Figure 63).

9. Rotate the camplate 2 notches counterclock-wise (viewed from the rear). See Figure 64. Fitthe main shaft shifting fork to third gear withthe fork grooves facing outward and install thegear on the main shaft while engaging the insidecam track with the pin on the fork (Figure 65).Install the main shaft second gear and bushingon the main shaft with the shifting dogs facinginward (Figure 66).10. Fit the layshaft selector fork to second gearwith the fork groove facing inward and installthe gear on the layshaft while engaging theoutside cam track with the pin on the fork(Figure 67).11. Install the fork pivot pin through the forks,threaded end first, and screw it into the case(Figurv 68).

108 CHAPTER FIVE

12. Install the bushing and first gear on thelayshaft (Figure 69). Then install the first gearon the main shaft with the shoulder on the gearfacing outward (Figure 70).

13. Apply a dab of grease to the quadrant rollerand set it in place in the end of the quadrant withthe hole in the roller positioned horizontal(Figure 71).

14. Refer to the earlier instructions in this chap-ter and install the inner and outer transmissioncovers. Refer to Chapter Four and install theclutch and primary drive.

C H A P T E R S I X

FUEL SYSTEM

The fuel system consists of the fuel tank, aircleaners, and carburetors.

CARBURETORS

Amal concentric float bowl carburetors areused on late model Norton twins. The carburetoris shown in exploded view in Figure 1. On someearlier models, such as the Atlas, Amal mono-bloc carburetors are used. This carburetor isshown in Figure 2. Twin carburetor models arefitted with a right-hand and a left-hand carbu-retor. The chief difference between the right andleft units is that the float "ticklers," the throttlestop screws, and air pilot screws are located onthe outboard side of each carburetor. If a car-buretor is to be replaced, be sure to specifyeither right or left when ordering.

Basic Principles

An understanding of the function of each ofthe carburetor components and their relationshipto one another is a valuable aid for pinpointinga source of carburetor trouble.

The carburetor's purpose is to supply andatomize fuel and mix it in correct proportionswith air that is drawn in through the air intake.At the primary throttle opening—at idle—asmall amount of fuel is siphoned through thepilot jet by the incoming air. As the throttle is

opened further, the air stream begins to siphonfuel through the main jet and needle jet. Thetapered needle increases the effective flowcapacity of the needle jet as it is lifted with theair slide in that it occupies decreasingly less ofthe area of the jet. In addition, the amount ofcutaway in the leading edge of the throttle slideaids in controlling the fuel/air mixture duringpartial throttle openings.

At full throttle, the carburetor venturi is fullyopen and the needle is lifted far enough to permitthe main jet to flow at full capacity.

Service

The carburetor service recommended at10,000-mile intervals involves routine removal,disassembly, cleaning, and inspection. Altera-tions in jet size, throttle slide cutaway, changesin needle position, etc., should be attempted onlyif you're experienced in this type of "tuning"work; a bad guess could result in costly enginedamage and at the very least poor performance.If after servicing the carburetors and makingthe adjustments described in Chapter Two, themotorcycle does not perform correctly (andassuming that other factors affecting perform-ance are correct, such as ignition timing andcondition, valve adjustment, etc.), the motor-cycle should be checked by a Norton dealer ora qualifled performance tuning specialist.

110 CHAPTER SIX

AMAL CONCENTRIC FLOAT CARBURETOR

Air valve guide

Air valve spring

Air valve

Carburetor body and tickler assembly

Air intake tube

Pilot jet(captive)

Spray tube

Needle jet

Jet holder

Main jet

Float needle

Securing screws

Filter

Banjo

Banjo bolt

Cable adjuster locknut

Cable adjuster

Securing screws

Mixing chamber top

Throttle valve spring

Needle clip

Throttle needle

Throttle valve

Tickler

0 ring for flange sealing

O-rings

Pilot air adjusting screw

Throttle stop adjusting screw

Float

Float chamber washer

Float spindle

Float chamber body

Removal

1. Close both fuel taps and disconnect the lines.Refer to Chapter Four and remove the fuel tank.

2. Disconnect the inlet bellows from the carbu-retor inlets (Figure 3).3. Remove the Allen screws which hold themanifolds to the cylinder head (Figure 4) andremove the carburetors from the motorcycle.

4. Remove the screws from the carburetor topsand pull out the slides (Figure 5).

Disassembly

1. Disconnect the balance pipe from the carbu-retors (Figure 6).

FUEL SYSTEM 111

AMAL MONOBLOC CARBURETOR

Cable adjuster [

Mixingchambercap springscrew

Mixingchambertop

Air valve

jet needle

clip

Cablenipple

Mixing body

Tickler body

Tickler andspring

Side cover screwSide cover^ Float spindle bushing

Float chamber

washer

Mixing chamber cap

spring

Mixing chamber cap

Air valve guide

Throttle valve spring

Air valve spring

Throttle valve

Jet needle

Jet block complete

Jet block washer

Seating washer

Banjo bolt

Washer

Banjo

Filter gauze

Needle seating

Air intake

NeedlePilot air adjustingscrew and spring

Jet blocklocating peg

Main jet_cover

Throttleadjustingscrew andspring

Pilot jet

Pilot jetcover washer

Pilot jet cover nut

112 CHAPTER SIX

3. Remove the 2 screws which hold the floatbowl to the carburetor and remove the bowl,float, float needle, and gasket (Figure 8).

4. Remove main jet and needle jet (Figure 9).

2. Unscrew the fuel banjo nut from the bottomof each carburetor and remove the banjo andthe filter screen (Figure 7).

1. Needle jet 2. Jet block 3. Main jet

5. Unscrew the air pilot screw and the throttlestop screw (Figure 10).

6. Unscrew the drain plug from the bottom ofthe float bowl (Figure 11).

7. Disconnect the carburetor from the manifoldpipe and remove the 0-ring (Figure 12).

FUEL SYSTEM 113

Cleaning and Inspection

1. The carburetors should be cleaned by sub-mersing all their metal parts in a cleaner that'sspecially compounded for carburetors and otherfuel system components. This type of cleaner isavailable under several brand names throughautomotive supply stores. In one-gallon sizes itfrequently includes a handy dip basket for hold-ing the parts while they are soaking. The partsshould remain in the cleaner for at least 5 min-utes. Solvent may also be used to clean the car-buretors, but it is not effective for dissolving theresidues that form as gasoline evaporates.

CAUTIONDon't clean the non-metal parts in acarburetor cleaning solution; it's harm-ful to such things as rubber O-rings,fiber gaskets, and the nylon float andneedle,

2. Remove the carburetor parts from the clean-ing solution and rinse them with water or solvent.Dry all of the parts thoroughly with a clean ragand blow out all the jets and the passages in thecarburetor body with compressed air.

3. Check the fioats for leakage by holding themup to a bright light to see if there is gasolinein them.

4. Check the tapered end of the float needle forgrooves, scores, or pits which would prevent itfrom shutting off the fuel flowing through theneedle valve.

5. Check each of the jets for blockage and anydamage that might alter the size of the flow area.Don't use wire to clean blockage from the jets,but instead blow them out with compressed air.

6. Check the throttle slide for wear and scoring.Minor surface imperfections can be removedwith fine emery cloth but if the slide is deeplyscored or severely worn it should be replaced.

7. Check the slide bore in the carburetor bodyfor wear or damage. Wear on the slide is oftenaccompanied by similar wear in the bore. Alsocheck the jet seats for damaged threads.

8. Check the throttle needle to make sure it isstraight and that the taper is not wom.

9. Check the taper of the pilot air screw forwear and grooving.

114 CHAPTER SIX

Reassembly

If possible, the O-rings, fiber washers, andfloat bowl gasket should be replaced each timethe carburetors receive major service. If any ofthese pieces are damaged or have deterioratedit's essential that they be discarded and replacedwith new pieces.

1. Screw the pilot air screw in all the way andthen back it out P/i turns. Make certain itsfriction O-ring is in place.

2. Screw in the throttle stop screw until the headprotrudes about 1/16 in. (Figure 13).

4. Invert the float bowl and set the float, floatneedle, and pivot pin in place (Figure 16). Setthe gasket in place on the flange and install it onthe carburetor. Screw in and tighten the 2 floatbowl screws. Install a fiber washer on drain plugand screw it into the bottom of the float bowl.

3. Screw the needle jet into the jet holder andscrew the holder into the carburetor body (Fig-ure 14). Screw the main jet into the holder(Figure 15). The jets should be tight but caremust be taken not to strip the threads.

5. Set the fuel strainer in the banjo fitting andinstall it on the bottom of the carburetor withthe flange on the strainer against the carburetorbody (Figure 17). Put a fiber washer on thebanjo bolt and screw it in tight.

6. Reinstall the carburetors on the engine byreversing the steps in the removal procedure.

FUEL SYSTEM 115

Before installing the Allen screws whichmount the manifolds to the cylinder head,thoroughly clean the screw threads and applya few drops of Loctite to them.

Assemble the needles and slides, making sureeach needle clip is in the same groove fromwhich it was removed. Install the slide assem-blies in the carburetors, taking care to line up

the needles with the needle jets and the verticalgrooves in the slide bores with the lug at the topof the slide. Reinstall the fuel tank and reconnectthe lines. Adjust the carburetors as describedin Chapter Two.

AIR FILTER

Service of the air filter element is describedin Chapter Two.

FUEL TANK

Removal/ Installation

1. Shut off fuel taps.

2. Disconnect fuel lines.

3. Remove the fuel tank. On Commando tanks,the front of the tank mounts on 2 studs beneaththe tank and is held by 2 self-locking nuts. Therear mount on some models uses a rubber loopwhich passes beneath the top frame tube. Othersare held in place with a metal cross bar.

4. Installation is the reverse of these steps.

c:

CHAPTER SEVEN

IGNITION AND ELECTRICAL SYSTEMS

The Norton Commando ignition system is abattery-coil type system with a centrifugallycontrolled automatic advance contact breakerfor spark timing control. The 1972 and latermodels are fitted with two 6-volt coils which areisolated from the 12-volt portion of the elec-trical system by a ballast resistor.

The Norton Atlas and G15 CS models use aLucas K2F magneto mounted behind the cylin-ders and driven by a chain connected to the cam-shaft drive idler in the timing side case. Routineservice of this unit is covered at the end ofthe chapter.

The charging-lighting system in all Norton750/850 twins uses an alternator (AC generator),A rectifier changes alternating current to directcurrent to charge the battery and power thelights. The charge rate to the battery is controlledby a zener diode.

IGNITION

Primary electrical power is supplied to theignition through the battery and charging cir-cuits. The advance mechanism and contactbreaker cam are driven off the camshaft sprocket

on the right of the engine. The firing point occursat 28° BTDC (fully advanced).

CONTACT BREAKER

Two similar contact breaker assemblies areused on Norton Commandos. On both types, thecontact set for each cylinder can be set inde-pendent of the other set. Different adjustmentprocedures are used for each type. Both typesshould be checked every 5,000 miles for contactcondition and point gap.

The Lucas 6 CA breaker assembly is fitted tomodels prior to 1973, There is a single lockscrew for each contact set and the fixed contactplate is moved with an eccentric adjuster. On1973 and later models, a 10 CA breaker assem-bly is used which has 2 lock screws for eachpoint set but no eccentric adjuster screws; duringadjustment, the plates must be moved with ascrewdriver tip.

Removal

1. Remove the ignition cover plate (Figure 1).2. Unscrew the nuts from the spring anchor

IGNITION AND ELECTRICAL SYSTEMS 117

posts and remove the terminals and movablecontact, along with the insulating bushing andwasher (Figure 2).

ing washer and bushing are installed in the ordershown in Figure 4.

3. Unscrew the lock screws from the fixed con-tact plates and remove the plates (Figure 3).4. Inspect the contacts for wear and pitting. Ifneither is excessive, the points can be dressedwith a flat point file and cleaned with lacquerthinner or acetone. Don't dress the points withemery cloth; this will round the edges of thecontacts and create the type of condition youmay be trying to correct. If the points can't bedressed with a few strokes of the file they shouldbe discarded and replaced with new parts.

Installation

Install the contact breaker assembly by re-versing the steps above. Make sure the insulat-

1. Lightly grease the pivot posts and the breakercam with breaker lubricant. Knead a couple ofdrops of oil into each of the felt lubricators.

2. Locate the tangs on the terminals over thecontact spring (Figure 5).

Adjustment

1. Remove the spark plugs from the cylinderhead and rotate the crankshaft to line up themark on the cam with the lifter heel on one ofthe contacts (Figure 6). This is the maximumcontact opening.

118 CHAPTER SEVEN

2. Measure contact gap with a flat feeler gauge(Figure 7). It should be 0.015 in. (0.38mm). Ifit is not, loosen the breaker lock screws (Fig-ure 8) and move the plate in or out until the gapis correct. Tighten the lock screw and recheckthe gap to make sure the plate did not movewhen the lock screw was tightened.

3. Rotate the crankshaft to line up the cammark with the other lifter heel and adjust thiscontact set in the same manner as above.

AUTOMATIC ADVANCE UNIT

The automatic advance unit (Figure 9), lo-cated behind the contact breaker plate, advancesignition timing as the engine speed increases.The unit is spring loaded and returns to thestatic timing position when the engine is shutoff. The unit may be serviced without removingit from the engine.

1. Mark the position of the contact breaker plate(Figure 10), unscrew the 2 plate-holding screws,and remove the plate with the contacts andterminals intact.

2. Lightly lubricate the pins and pivots on theadvance unit.

3. Check to see that the ends of the springs areseated in their recesses in the bobweights and onthe raised tangs in the fixed plate (Figure 11).

4. Turn the cam by hand to the fully advancedposition to extend the bobweights. Then release


IGNITION TIMING

Ignition timing can be accomplished in oneof two ways, either statically or dynamicallywith the use of a timing strobe. The staticmethod is accurate enough for most situationsbut strobe timing is essential for complete timingaccuracy required for maximum performance.

Static Timing

If the breaker cam has been removed andreinstalled, it must first be correctly located onthe shaft before the ignition can be timed. To dothis, first remove the intake and right-handrocker exhaust covers and the spark plugs. Ro-tate the crankshaft clockwise to bring the rightpiston to TDC with both valves closed (firingposition). Use the wire color coding to determinewhich contact set fires the right cylinder. Turnthe breaker cam on the shaft counterclockwiseuntil it just begins to open the right cylinderpoints and tighten the bolt in the end of theshaft (Figure 12).

it. If the springs are in good condition, the bob-weights will snap back to the static position. Ifthey do not, the springs should be replaced.5. Reinstall the contact breaker plate, makingsure the marks are aligned. Recheck the contactgap and the ignition timing.

1. Check the contact gap as described earlierand adjust it if necessary.2. Remove the inspection plug from the primarychaincase (Figure 13).3. Remove the bolt and washer from the end ofthe breaker cam shaft and install a washer witha large enough hole to pass over the end of theshaft and contact the face of the cam (Figure 14).Reinstall the bolt and washer in the shaft, hold

120 CHAPTER SEVEN

the advance unit at full advance, and tighten thebolt to hold the advance unit in place.

4. Shift the transmission into fourth gear androtate the rear wheel to bring one of the pistonsto TDC with both valves closed. Slowly rotate thewheel backward to align the timing mark withthe 28° mark on the degree plate (Figure 15).At this position, the contact breaker for thecylinder being timed should just begin to open.

5. To determine the precise opening point, in-sert a strip of thin paper between the contacts.Slowly rotate the crankshaft until the paper canbe withdrawn with a slight pull. This is the pointat which contact opening begins.

6. Check the alignment of the timing mark withthe degree plate. If the timing is correct, themark should line up with the 28° mark.

7. If the timing is not correct, align the timingmark at 28° and loosen the 2 screws which se-cure the contact breaker plate (Figure 16). Insert

the paper between the contacts for the cylinderbeing timed and rotate the breaker plate clock-wise or counterclockwise as required until thepaper can be withdrawn with a slight pull. Thentighten the breaker plate holding screws.

8. Check the timing of the opposite cylinder inthe same manner. If the timing must be adjustedfor this cylinder, loosen the screws holding thesecondary cjontact plate (Figure 17), move theplate as required until the timing is correct, andsecurely tighten the screws.

9. Double check both the timing and the contactgap or both cylinders and both sets of contacts.


Dynamic (Strobe) Timing

Before the ignition can be timed with a strobe,the contact gap and static timing must be ad-justed as described above.

1. Remove the inspection plug from the pri-mary chaincase.

2. Connect the strobe to the high-tension leadon the right cylinder.

3. Start the engine and run it at 3,000 rpm.

4. Point the strobe light at the indicator plate inthe chaincase. The rotor mark should line upwith ;he 28° mark on the degree plate. If it doesnot, loosen the 2 screws which secure the contactbreaker plate and rotate the plate clockwise(advance) or counterclockwise (retard) until themarks line up correctly. Then tighten the screwsin the contact breaker plate. Shut off the engine.5. Connect the strobe to the high-tension leadon the left cylinder, start the engine and run itat 3,000 rpm and check the timing for the leftcylinder in the same manner as for the right. Ifthe rotor mark does not line up with the 28°mark, loosen the screws in the secondary contactplate, move the plate as required until the marksline up, and tighten the screws.6. After both cylinders have been timed, re-check them again with the strobe to ensure thatneither of the contact plates has moved.

NOTE: / / the timing mark tends tojump around during strobe timing,check the adjustment of the camshaftchain and the tightness of the alter-nator rotor. Also, a loose rotor willoften sound like lower end trouble.

COILS

Both 6- and 12-volt coils are used, in pairs, onNorton Commando electrical systems. The6-volt coils are isolated from the rest of the 12-volt electrical system by a ballast resistor. Thecoils should be checked to see that they aremounted securely and that their connections areclean and tight; no other service is necessary.

If a coil is suspected of being faulty it can bepartially tested by checking the resistance of theprimary windings. To do this, connect an ohm-meter across the primary terminals. At an am-bient temperature of about 70°F the resistancein a 6-volt coil should be at least 1.7 ohms butnot greater than 1.9 ohms. For a 12-volt coil,the resistance should be at least 3.3 ohms butnot greater than 3.8 ohms. If the resistance ofthe primary windings is all right, the coil shouldbe taken to a shop specializing in automotiveand motorcycle electrical work for further test-ing. Even better, substitute a known good coilto check a suspected coil.

Ballast Resistor

The ballast resistor used with 6-volt coils canbe checked with an ohmmeter. Resistance shouldbe 1.8-2 ohms.

CAPACITORS

The ignition capacitors can be tested whileinstalled on the motorcycle. First, remove thefuel tank and the contact breaker cover plate.Rotate the crankshaft to open one of the contactsets. Connect a voltmeter to the contacts andturn on the ignition switch. If no voltage is indi-cated the capacitor should be replaced. Rotatethe crankshaft to open the other contact set andcheck it in the same manner.

If voltage is present but the capacitors arestill suspected of not being within service limits(evidenced by hard starting or erratic running),check the contacts for signs of burning—an indi-cation that the capacitor is failing.

Capacitors on early models can be removedand replaced by unscrewing them from the coilclips. On 1971 and later models, remove theentire coil assembly from the motorcycle andthen remove the capacitor pack from the coilassembly (Figure 18).

122 CHAPTER SEVEN

Ballast resistor Y ^ ^ ^ -

Capacitor pack ^ ^ \

COIL ASSEMBLY

Ignition coil

^ ^^iSS ignition coii

^^^•^^ Warning \ \light assimilator \ \

Suppressed hightension leads

NX

SPARK PLUGS

For normal use, and for all models exceptthe 750 Combat, Champion N7Y spark plugsare recommended; however, equivalent plugs ofdifferent manufacture can be used provided theirheat range corresponds to that of the N7Y. Plugswith an incorrect heat range can cause hardstarting at one extreme, or preignition at theother, resulting in possible engine damage.

Champion N6Y spark plugs are recom-mended for use in the 750 Combat and forsustained high-speed operation.

The spark plug electrode gap should be0.028 in. (0.71mm).

CHARGING SYSTEM

The charging system consists of the alterna-tor, current rectifier, zener diode regulator, andheat sink. The charging system requires noservice other than periodic inspection of the

connections to ensure they are clean and tight.When trouble occurs in the charging system,

the components can be checked while installedon the motorcycle. The wiring diagrams at theend of this chapter will be helpful for locatingand testing the components and circuits referredto in the text.

ALTERNATORTesting

1. Unplug the alternator leads from the wiringharness (Figure 19).2. Connect a voltmeter (set to AC scale) witha one ohm resistor wired parallel to the alter-nator leads.

3. Start the engine and run it at a steady 3,000rpm. The meter should indicate a minimumof 9 volts.4. Measure the voltage between each of theleads and ground. There should be no reading.


5. If there is no reading in Step 3, an open cir-cuit is indicated in the coil circuit. In such case,the rotor should be replaced. If the reading wassubstantially less than 9 volts, it's again possiblethat the rotor is faulty. This can be verified byinstalling a new rotor and checking it as de-scribed above.

6. If the readings were correct, connect theblack lead of an ammeter to the battery negativeterminal and the red lead of the meter to thenegative cable.7. Disconnect the zener diode (Figure 20).

8. Start the engine and run it at a steady 3,000rpm. With the ignition switch in the IGNITION

ONLY position, the ammeter should indicate acharging rate of at least 4.5 amps. With the igni-tion switch in the LIGHTS AND IGNITION position,the ammeter should indicate a charging rate ofat least 1.0 amp. If the ammeter readings arehigher than these, the system is all right. If theyare not, continue with the next steps and checkthe condition of the rectifier.


To remove the alternator rotor and stator,perform Steps 1-6, Primary Drive and ClutchDisassembly, Chapter Four. To install, performSteps 10-15, Primary Drive and Clutch Assem-bly, Chapter Four.

RECTIFIERTesting

1. Check to make sure the alternator leads arecorrectly connected to the main harness and thatthe connections are clean and tight.

2. Unplug the center lead from the rectifier(Figure 21) and connect the black (—) lead of avoltmeter (set to DC scale). Ground the volt-meter red ( + ) lead to the frame.

From harness Remove thecenterconnector

DCvoltmeter

3. Start the engine and run it at a steady 3,000rpm. The meter should indicate at least 7.5volts. If it indicates less, the rectifier is unsatis-factory and should be replaced. If the readingis satisfactory, proceed to bench test the rectifierto verify that it permits current to flow in onlyone direction.

4. Using a pair of test leads, connect a headlightbulb to the battery as shown in Figure 22.5. Clip the other ends of the test leads to eachcombination of rectifier terminals shown belowfirst in one polarity and then in the other. Eachhookup should be made for more than a fewseconds at a time.

124 CHAPTER SEVEN

a. Terminals 1 and 2

b. Terminals 2 and 3

c. Terminal 1 and bolt

d. Terminal 3 and bolt

If the bulb lights in both directions on any onehookup, or if it lights in neither direction on anyone hookup, the rectifier is defective and mustbe replaced.

ZENER DIODETesting

1. Unplug the electrical cable from the zenerdiode and connect the red (+ ) lead of a DCammeter to the Lucar blade on the diode andthe ammeter black (—) lead to the cable (Fig-ure 20). Connect the black (—) lead of a DCvoltmeter to the Lucar blade and the voltmeterred ( + ) lead to ground. See Figure 23.

VOLTMETERBlack

AMMETERBlack

2. With all the lights switched off, start theengine. Slowly increase the engine speed andobserve the 2 meters. Up to 12.75 volts, as indi-cated by the voltmeter, the ammeter shouldindicate nil current flow. From 13.5-15.5 volts,the ammeter should indicate a current flow of 2amps. If current begins to flow before the volt-meter indicates 12.75 volts, or if the voltmeterindicates more than 15.5 volts before the am-meter reaches 2 amps, the diode is unsatis-factory and must be replaced.

Before installing the dicie, lap its contactsurface to the contact surface on the footrestusing a fine grade of lapping compound. Thefootrest functions as a heat sink to help thediode dissipate heat produced by the alternatorwhen the battery is fully charged and the lightsare off. For this reason it is essential that therebe a good contact between the diode and thefootrest. In addition, a thin coat of siliconecompound, such as G.E. Electronic SiliconeCompound Transistor Z-5 No. 8101 or G.E.Silicone Compound G-640 or G-641, should beapplied to the contact area before installing thediode. This compound is available through TVrepair shops and electronic supply houses.When the diode has been installed, tighten themounting nut to 24-28 in.-lb., taking care notto strip the soft copper threads.

BATTERY

Service battery as described in Chapter Two.

BATTERY CROSSBARMODIFICATION

On many 850 Mark II models built betweenengine numbers 307311 and 32500, the rec-tifier is installed in such a manner that the bat-tery hold-down crossbar can foul the electricalleads to the rectifier should the battery shiftbackward in its holder. To reduce the likelihoodof this occurring, cut about one inch off eachend of the battery crossbar—about midway be-tween the notches (Figure 24). Dress the sawededges with a fine file to remove burrs and sharp-ness and spray paint the raw metal to inhibitcorrosion.


STARTER (850 MARK

Service to the starter is limited to replacementof the brushes. If additional work is required,the starter should be entrusted to a Nortondealer or an electrical specialist.


1. Disconnect the ground lead at the fuseholder. Disconnect the electrical lead from thestarter motor (Figure 25).2. Remove the 2 screws from the startermounting boss on the primary case and the longscrew from the outer chaincase cover (Fig-ure 26). Pull the starter motor out of the mount.

3. Reverse the above to install the starter. Makesure the large O-ring is in good condition beforeinstalling the motor. Tighten the nut on theelectrical post securely and fit the rubber cover.

Brush Replacement

1. Remove starter motor as described above.

2. Unscrew the 2 through bolts from the rightend of the starter and remove the end cap(Figure 27). Note the position of the brushholder plate and remove it.

3. Remove the springs and brushes from theplate and install new ones. Reinstall the platein the starter in the same position from which

it was removed, making certain the brushes arein contact with the armature.4. Install the end cap and screw in the throughbolts. Install the starter as described earlier.

Relay

If the starter relay energizes but the starterfails to turn over, check the connections of therelay-to-starter electrical lead to make sure theyare tight and corrosion-free. If the starter stillfails to turn over it may need new brushes.

126 CHAPTER SEVEN

24


ELECTRIC STARTER

1.2.3.4.5.6.7.8.9.

10.11.12.13.14.15.16.17.18.19.20.21.22.23.24.25.26.27.28.29.30.31.32.33.34.35.36.37.38.39.40.41.

(850 MARK III)

O-ring

Screw

Long screw

Idler spindle

Idler gear

Idler gear

Ball

Thrust washer

NutDisc spring

Carrier

Gear

Thrust washer

Shaft

Circlip

Circlip

Thrust washer

Clutch

Crank gear

Needle roller bearing

Inner washer

Inner race

Outer washer

Starter motor

Armature

Brush

Head assembly (commutator end)

Head brush and seal (drive end)

Brush plate and holder

Spring

Thru-bolt

Thrust washer

Solenoid

Solenoid bracket

Starter ground lead

Battery to solenoid lead

Solenoid to starter lead

Solenoid bracket bolt

Bolt

Washer

Nut

If all of the connections are clean and tightand the relay does not energize, it is very likelyfaulty. In such case, remove the relay and haveit checked by a Norton dealer or an electricalspecialist to verify its condition.

LIGHTS AND SWITCHES

Service of the lights and switches is limited tochecking connections to make sure they areclean, dry, and tight.

Fault tracing and replacement of most of thelighting and switching components is simple andstraightforward. However, the adjustment of therear brake stoplight switch must be done care-fully to prevent damage to the unit, and thefunctional test procedure of the directionallights flasher relay should be followed to deter-mine if the flasher unit itself is at fault whentrouble occurs in this circuit.

Rear Brake Stoplight Switch

1, Loosen the bolts which mount the switch tothe brake pedal (Figure 28).

B

2. Adjust the brake pedal stop (Figure 29) sothat the pedal position is comfortable. Adjustrear brake free play, described in Chapter Two.

3. Slowly move the switch up, positioning theswitch plunger in the center of the contact bosson the foot peg, until the slightest downwardmovement of the brake pedal causes the stop-light to light. The movement of the switchplunger, from full extension to the point at

128 CHAPTER SEVEN

which the pedal contacts the pedal stop, shouldbe about 1/32 in, (0.79mm).4. Tighten the switch mounting bolts and re-check the adjustment. The switch plunger mustnot be fully depressed before the pedal contactsthe stop.

Directional Light Flasher

1. Check the directional lamp bulbs to makesure the filaments are not broken and check tosee that all the connections are clean and tight.

2. Switch on the ignition and check the voltageof the "B" terminal on the flasher with a volt-meter. The meter should indicate batteryvoltage (12 volts).

3. Using a test lead, connect the "B" and "L"terminals on the flasher together and operate theflasher switch in both directions. If both lampson one side light but do not flash, the relay isfaulty and should be replaced.

MAGNETO SERVICE

Routine periodic service on the Lucas K2Fmagneto used on Atlas and G15 CS models,presented here, is within the ability of the hob-

byist mechanic. However, major service of theunit, recommended at 10,000-mile intervals,should be referred to a Norton dealer or anelectrical service specialist with experience onthis particular unit.

Cleaning

1. Remove the contact breaker cover. Unscrewthe long hex-head screw from the center of thebreaker assembly (Figure 30) and pull theassembly off the shaft.

2. Inspect the contacts for burning and pitting.If their condition is reasonably good, dress themwith a point file; do not use emery cloth as it willround the edges of the contacts. Clean the pointsthoroughly with lacquer thinner or acetone andgrease the breaker cam ring with contact breakerlube. Apply a drop of oil to the end of thepivot post.

3. Reinstall the contact breaker assembly, mak-ing sure the keyway in the shaft lines up with theprojection in the bore of the cam.

4. Lift the hold-down springs from the high-tension brushes and check the movement of thebrushes in their holders. They should movefreely in and out. If they do not, clean them with


Fixed contactpiate securingscrew

Movingcontact

C.B. securingscrew

Push-on retainingring

Contact breakerlever

Fiber washers

Fixed contact

Fixed contactplate

Pivot post

lacquer thinner or acetone. Check them also forwear. If they are worn down to within Vs in. ofthe shoulder, they should be replaced.5. Inspect the contact track for dirt and corro-sion. To clean, insert a small length of dowel.

wrapped in clean cloth, in one of the brushholders and slowly rotate the engine.6. Reinstall the brushes, making sure the hold-down springs are correctly positioned, and ad-just the contacts as described below.

Adjustment

1. Remove the spark plugs from the cylinderhead and rotate the engine until the contacts arefully opened. Measure the gap; it should be0.012 in. (0.30mm) and there should be aslight resistance on the feeler gauge when it isinserted and removed.

2. If the gap is incorrect, loosen the securingscrew for the fixed contact (Figure 31) and moveit in or out until the setting is correct. Thentighten the securing screw and recheck the gap.

Fixed contact plate securingscrew

0.012 in. 0.015 in./

Screwdriver

WIRING DIAGRAMS

Wiring diagrams will be found on the following pages:

750cc Atlas and G15CS, 650cc Manxman,

S.S., and 12 Volt Twin Magneto Ignition 130

750cc Commando (Before 1971) . . . . 131

750CC Commando (1971) 132-133

85OCC Commando Mark II (1972-1974) . . 134-135

850cc Commando Mark III (All Years) . . 136-137

130 CHAPTER SEVEN

WIRING DIAGRAM - 650cc and 750cc(Atlas, GT5CS, Manxman, S.$., and 12 Volt Twin Magneto Ignition Models)

H

000

oz

zou

zX

7

^ ^ .̂ I ^ £(T CO S >- Q HJ £II II II II II II ^

or 00 ^ >• Q -J 3

3 ^ ^g i5 ^ £ £ E 3 •

OD QQ m o a. Q- '


WIRING DIAGRAM - 750 Commando (Before 1971)

a o ccl-o-c XL.

0

<

Ui

°l ° -PA

ILO

T

" • • • a

All

> O p

<a<MiX

\ti

z

o

ss

I2 £E 3^!2£-S c5

132 CHAPTER SEVEN

WIRING DIAGRAM

ALTERNATING HORNS CIRCUIT

NP"

FRONT BRAKESWITCH

R/H HANOLEBARSWITCH

. Denotes Interpol Circuits


197T 750 Commando

CAPACITOR-:==.

N J—iSTOP^ h^^^—'UCSiT I'

COLOR CODE

U = BlueB = BlackN = BrownG — GreenK = PinitP — PurpleR - RedS = Slate grey

W = WhiteY = YellowD = DarkL = Light

M = Medium grey

134 CHAPTER SEVEN

WIRING DIAGRAM

ALTERNATING HORNS CIRCUIT

NP"

PB~

L6/N

FRONT BRAKESWITCH0—b

•I J L R / H DIRECTION'I ' ' ^ * INDICATOR

R/H HANDLEBARSWITCH

.. Denotes Interpol Circuits


1972-1974 850 Commando Mark II

COLOR CODE

B = BlackU = BlueN =: BrownG = GreeriK = PinkP = PurpleRzzRedS = Slate grey

W = WhiteY = YellowD = DarkL = Light

M = Mediund grey

136 CHAPTER SEVEN

WIRING DIAGRAM

FRONT

CUTCXJTSTART

HEADPILOr

EARTMi.TOHEADLAMP

SHELL

FLASH

HORNDIP

MAINRH J

INDICATORLH

MASTER Sy^nCHPOSTTiONS


850 Commando Mark III (All Years)

ALTERNATOR

3Y

i

R

ZENER- - D I O D E

MAIN

NURECTIFIER

HARNESS

<5Y [ > 1 , IWSAt. I M . . . .

DTE1

NG

SEE

WN

BATTERY

UNITS p V L I G H T

EARTH TOCOL BRACKEtT

ASSYIII R

_ W KE l 5 ^ ,

TACHO rNOT USED

mMAIN

iiUW

JLW

UJ

NEUTRAL INDICATOR

W

WYIGNITION - SUB,HARNESS

P3

SWITQi

REARBRAKSIDE

Q ^

N G ^ , ^ JAIL ..RE A R .RH. INDICATOR '

-I II EARTH

COLOR CODE

B - BlacitU = BlueN = BrownG = GreenK = PinkP = PurpleR = RedW = WhiteY = YellowL =: LightS = Slate grey

GR—

. INDICATOR

INDICATOR NEUTRAL IQ^ITION

WARNING LIGHT CONSOLE

NOTE: 1 : Canadian models have headlight warning unit in place

of ignition warning light unit connections.

R&W

NOTE

H L :

W L :(U)(WN)

wires not used on

2: Indicator leads

TL: (NG)

ALAL

Canadian models.

are not color coded.

:(GY):(WG)

C H A P T E R E I G H T

FRONT WHEEL AND BRAKE

This chapter describes repair and mainte-nance of the front wheel, hub, drum brake, anddisc brake.

FRONT WHEEL

Removal/Installation

1. Block up the front of the motorcycle to liftthe front wheel off the ground.

2. On models with a drum type front brake, dis-connect the brake cable from the lower brakearm by removing the clevis pin (Figure 1). Un-screw the cable adjuster from the boss on thebrake and backing plate.

3. On all models, unscrew the axle nut (Fig-ure 2). Loosen the pinch bolt at the bottom ofthe left leg (Figure 3). Insert the shaft on a screw-driver or small bar through the hole in the leftend of the axle and pull it out of the forks andwheel while lifting and supporting the weightof the wheel.

4. On disc brake models, pull wheel forward todisengage the disc from the caliper.


FRONT DRUM BRAKE

Two types of drum brakes are used on NortonCommandos. On the standard brake, the shoes

are retained on the pivots with circlips (Fig-ure 4). On the modified high-performance brake,with the expander plate, the plate and shoes areheld in position with bolts secured by tab wash-ers (Figure 5). Both brakes are double-leading-shoe type units.

FRONT WHEEL AND BRAKE 139

ilSet screwTab washer

Pivot pinExpander cam

Disassembly

1. Block up the front of the motorcycle to liftthe front wheel off the ground. Remove it asdescribed in this chapter. Then remove the com-plete brake assembly from the drum.

2. Position the brake backing plate horizontallyin a vise and clamp it by the brake anchor peg.3a. On the standard brake, remove the circlipsand washers from the shoe pivot pins.

3 b. On the modified brake, straighten the tabwashers on the pivot bolts and unscrew the bolts.Remove the expander plate by carefully pryingthe plate up with a screwdriver inserted betweenthe plate and the shoes, to the right of each of theexpander cam pivots.4. Remove the return springs by lightly grippingthe coil section with a pair of conventional pliersand extending one of the spring ends withneedle-nose pliers. Then remove the brake shoes.

5. Remove the backing plate from the vise andunscrew the nuts which hold the brake arms tothe cams. Remove the arms from the camshaftsand pull the cams out of the backing plate.

Inspection

Thoroughly clean and dry all the parts exceptthe linings. Check the contact surface of thedrum for scoring. If there are grooves deepenough to snag a fingernail, the drum should beentrusted to a brake specialist to have it trued.In such case, the linings will have to be replacedand the new ones arced to the new drum contour.

I

140 CHAPTER EIGHT

Check the linings for wear as described above.If they are serviceable, inspect them for im-bedded foreign material. Dirt can be removedwith a stiff wire brush, but if they are soakedwith oil or grease they will have to be replaced.

Inspect the cam lobes and the pivot area of theshaft for wear and galling. Minor roughness canbe removed with emery cloth but if either areais deeply scored or severely worn, the camshould be replaced. In addition, check the ex-pander cam bushings and replace them if theyare worn or galled.

Assembly

Assemble and install the front brake andwheel by reversing the disassembly steps. Greasethe shafts and contact areas of the expandercams, the bushings in the cam bores, and thebrake shoe pivot posts with a light coat of amolybdenum disulfide grease; excess grease islikely to find its way onto the brake linings andrender them unserviceable.

On a modified brake, don't enlarge the pivotor cam holes in the support plate to get it to fitmore easily; to do its job, the plate must fittightly so that it can maintain the pivots andcams in a constant relationship.

After the front wheel has been installed inthe motorcycle, adjust the brake as describedbelow. Before tightening the axle nut, spin thefront wheel and apply the front brake. Hold thebrake on to locate it centrally in the drum andtighten the axle nut securely.

Adjustment

1. Remove the clevis pin from the top brake arm(Figure 1).2. With assistance, pull both of the brake armsdown to bring the shoes in contact with thedrum and hold them there.

3. Turn the link adjuster either in or out untilthe clevis can be installed with a light push fit.Tighten the locknut on the link.

4. Adjust the control cable so that the brake isapplied with a slight movement of the hand leverbut the shoes do not drag in the drum when thelever is relaxed. Hold the adjuster to prevent itfrom turning and tighten the locknut.

FRONT DISC BRAKE

The front disc brake is actuated by hydraulicfluid and is controlled by a hand lever like thedrum-type brake. Unlike the drum brake, how-ever, the disc brake does not require adjustment.

It's essential that the work area and all toolsbe scrupulously clean when doing any majorservice on the hydraulic system. Tiny particlesof foreign matter and grit in the caliper assemblyor the master cylinder can damage the com-ponents making the system unsafe and requiringreplacement of the damaged parts. Also, sharptools must not be used inside the calipers or onthe pistons. If there is any doubt about yourability to correctly and safely carry out majorservice on the brake components, take the jobto a Norton service shop or a brake specialist.

Master Cylinder Removaland Disassembly

1. Unplug the electrical leads from the brakelight switch (Figure 6). Peel the rubber bootaway from the switch and master cylinder toexpose the brake line nut. Unscrew the nutand 4 screws which hold the master cylinder tothe handlebar (Figure 7).

2. Remove the cap and bellows from the mastercylinder and unscrew the brake light switch.Unscrew the pivot nut and bolt (Figure 8) andremove the lever.


3. Remove the circlip from the end of the mas-ter cylinder by carefully prying out several ad-jacent tangs on the clip. Remove the rubber bootand the piston.

4. Remove the cups, washer, and spreader fromthe master cylinder by lightly tapping the openend of the cylinder on a clean piece of wood orby applying light air pressure to the brake-lineport. Do not use any hooks or sharp objects topull the pieces out of the cylinder.

MASTER CYLINDERASSEMBLY

Lever

Cap

Beilowsseal

Boot

Trap or bleedvalveassembly

Body

p (10 ears)

Brake light switch

Boot

Piston assembly

Secondary cupPrimary cup washer

Primary cup

142 CHAPTER EIGHT

Inspection

1. Thoroughly clean the piston and mastercylinder in fresh brake fluid and allow them todrain on a clean surface. Inspect the master cyl-inder bore and the piston contact surfaces forsigns of wear and damage. If either componentis less than perfect, replace it. Check the end ofthe piston for wear caused by the lever andcheck the pivot bore in the lever. Discard thebleed valve assembly, rubber boot, and cups.

2. Make sure the passages in the bottom of thebrake fluid reservoir are clear. Check the reser-voir cap and bellows for damage and deteriora-tion and replace as necessary. Finally, check thecondition of the threads in the bores for thebrake line and the switch and examine the leverpivot lug for cracks. Any one instance of wearor damage to either the master cylinder or pistonis reason for replacement of the affected com-ponent.

Assembly

1. Soak the new seal cups in fresh brake fluidfor at least 15 minutes to make them pliable.Carefully work the secondary cup on the pistonover the primary flange and into its grooveby hand.2. Install the boot on the piston. Make sure theouter end of the boot seats in the piston groove.

3. Assemble the trap valve, spring, and spread-er. Make sure the plastic bobbin seats in thelarge end of the spring and the spreader seats inthe small end. The hole in the bobbin mustbe clear.4. Hold the cylinder upright and install theassembly, valve flrst. Set the primary cup intothe cylinder, open end down, and set the washeron top of it with the convex surface up.

5. Coat the secondary cup with brake fluid andset the piston into the cylinder, crown first. Setthe lock clip in place on the end of the boot withthe clip fingers facing away from the boot.

6. Slowly turn and press in the piston assemblyat the same time. Make sure that the lip of thesecondary cup enters the cylinder without snag-ging. When the piston portion of the assemblyis in the cylinder, hold it in place and fit theshoulder of the boot into the groove in the cylin-

der. Fit the boot lock clip into the groove. Whilestill holding the piston assembly in the cylinder,engage the end of the piston assembly with thelever, line up the lever pivot holes, and installthe pivot bolt and nut.

7. Reinstall the master cylinder by reversing theremoval steps. Check to make sure the mastercylinder is horizontal on the handlebar and filland bleed the system.

Bleeding

1. Connect a length of tubing to the bleed valveon the brake caliper and place the other end ofthe tube in a clean, glass jar. The tube should belong enough so that a loop can be made higherthan the bleed valve to prevent air from beingdrawn back into the caliper during bleeding,

2. Fill the fluid reservoir almost to the top lip.Open the bleed valve a full turn and slowly pumpthe hand lever. As the fluid enters the system, thelevel will drop in the reservoir. Maintain thelevel at about Vi inch from the top of the reser-voir to prevent air from being drawn into thesystem.3. Continue to pump the lever and fill the reser-voir until there are no more air bubbles in thefluid coming from the bleed line. Then hold thelever full on and tighten the bleed valve andremove the bleed tube.4. If necessary, add fluid to correct the level inthe reservoir. It should be Vi inch from the topedge (Figure 9). Install the rubber bellows,closed side down, and screw on the reservoir cap.


5. Test the feel of the brake lever. It should befirm and should offer the same resistance eachtime it's pulled. If it feels spongy, it's likely thatthere is still air in the system and it must be bledagain. When all air has been bled from the sys-tem, and the fluid level is correct in the reser-voir, double check and tighten all the fittingsand connection.

WARNINGBefore riding the motorcycle, makecertain that the front brake is operativeby compressing the lever several times.

Brake Pad Replacement

There is no recommended mileage intervalfor changing the friction pads in the disc brake;service life is heavily dependent on riding condi-tions and habits. The disc and pads should bechecked for wear every 1,000 miles and replacedwhen the friction material is worn down to athickness of about Vs in. (3.2mm).

1. Remove front wheel as described earlier.

2. Carefully remove the pads from the caliperand discard them. Clean the pad recesses andthe ends of the pistons with a soft brush. Don'tuse solvent, wire brush, or any hard tool whichwould damage the cylinders or the pistons.

3. Lightly coat the ends of the pistons and thebacks of the new pads (not the friction material)with disc brake lubricant.

NOTE: Check with your dealer tomake sure the friction compound ofthe new pads is compatible with thedisc material. Remove any roughnessfrom the metal backs of the pads witha fine file and blow them clean withcompressed air.

4. Remove the cap and bellows from the mastercylinder and slowly push the pistons into thecaliper while checking the reservoir to make surethe fluid does not overflow. The pistons shouldmove freely. If they do not and there is anyevidence of them sticking in the cylinders, thecaliper should be removed and serviced asdescribed later.

5. Install the pads in the caliper and push themall the way in against the pistons.

6. Carefully remove any rust or corrosion fromthe disc and install the front wheel. With thefront of the motorcycle still supported, spin thefront wheel and activate the brake for as manytimes as it takes to refill the cylinders in thecaliper and correctly locate the pads.

WARNINGDon't ride the motorcycle until you'resure the brake is operating correctlywith full hydraulic advantage.

7. Bed the pads in gradually for the first 50miles by using only light pressure as much aspossible. Immediate hard brake applications willglaze the new friction material and greatly re-duce the effectiveness of the brake.

Caliper Rebuilding

If the caliper cylinders leak, the caliper shouldbe rebuilt. If the pistons bind in the cylinders,indicating severe wear or galling, the entire unitshould be replaced. Rebuilding a leaky caliperrequires special tools, a super-clean work en-vironment, and experience. Even minor damageto the cylinders, pistons, or seals during service,or an assembly error could cause the brake tomalfunction. Therefore, caliper service shouldbe limited to removal and replacement. Take anunsatisfactory caliper to an authorized Nortondealer or to a brake specialist with experience onthis particular unit for rebuilding.

Caliper Removal

1. Unscrew the pipe union at the hose bracket(Figure 10). Loosen or remove 2 nuts whichfasten the fender bridge and hose bracket to thefork leg so the hose and pipe can be separatedwithout bending the pipe.

144 CHAPTER EIGHT

2. Unscrew the caliper mounting bolts (Fig-ure 11) and slide the caliper off the disc.

Caliper Installation

Install the caliper by reversing the removalsteps. Fill the system with brake fluid and bleedit as described earlier. Make certain that thebrake is fully operative before riding themotorcycle.

FRONT HUB

The front wheel should be removed and thehub disassembled, inspected, and the bearingscleaned and greased every 10,000 miles.

Disassembly/Assembly (Drum Type)

1. Block up the front of the motorcycle so thewheel is oflF the ground and remove it as de-scribed earlier.

2. Unscrew the lock ring (right-hand thread)from the left side of the hub (Figure 12) withNorton tool No. 063965, or by applying the endof a small drift against the side of one of therecesses and tapping the ring loose. If the ringcannot be broken loose, warm the hub with apropane torch or similar low flame.

3. Remove the seal and the spacer from the leftside of the hub and install the axle from theright side. Using the axle as a drift, tap it intothe hub with a soft mallet. As the right sidebearing and the spacer are driven into the hubthey will displace the left-side bearing. Drive itonly as far as necessary for it to drop out.

4. Remove the axle and install it in the left sidethrough the spacer tube. Drive out the right-sidebearing along with the washers and seal.

5. Clean and dry the parts thoroughly. Checkthe bearings by hand for roughness and radialplay and inspect the seals for damage or deteri-oration and replace any pieces that are defec-tive. Pack the bearings with grease.

6. Line up the left-side bearing squarely withthe bore in the hub and tap it into place, apply-ing a drift only to the outer race. Install thespacer (with the flat side against the bearing),the seal, and the lock ring. Tighten the lock ringsecurely.

7. Install the spacer into the left-side bearingthrough the right side of the hub. The short endof the spacer must go into the left bearing andthe spacer must be driven all the way in until itsshoulder contacts the bearing inner race. Fillthe area between the spacer and the inside of thehub with grease.

8. Line up the right-side bearing (double row)squarely in the right bearing bore. Using the axleas a drift, drive the bearing into the hub until itcontacts the shoulder on the spacer,

9. Install the small washer, seal, and largewasher. On early models it may be necessary totap the large washer on.

10. Assemble the brake to the hub and installthe wheel. Centralize the brake in the drum asdescribed under Front Drum Brake Assembly.

11. Adjust the brake as described earlier.

Disassembly/Assembly (Disc Type)

1, Block up the front of the motorcycle so thewheel is off the ground and remove it as de-scribed earlier.

2, Unscrew the lock ring (left-hand thread)from the left side of the hub (Figure 13) usingNorton tool No. 063965, or by applying the endof a small drift against the side of one of therecesses and tapping the ring loose. If the ringcannot be broken loose, warm the hub with apropane torch or similar low flame,

3. Remove the seal and spacer and heat the hubwith water to about 212°F (100°C),

4. Insert a drift through the double-row bearingand into the spacer tube. Move the opposite end


FRONT HUBDRUM TYPE BRAKE

1. Wheel assembly2. Spindie nut3. Wheel spindie4. Bearing5. Bearing lock ring6. Dust cover7. Spacer8. Right-side bearing9. Spacer

10. Washer11. Seai12. Washer13. Rim14. Inner spoke15. Outer spoke16. Spoke nipple

17. Nut18. Hub shell19. Adjuster nut20. Inlet gauze21 . Exit gauze22. Air scoop screw23. Air iniet cover24. Air exit cover25. Brake shoe26. Expander27. Slipper28. Brake shoe spring29. Tie rod30. Yoke (left-hand thread)31 . Yoke (right-hand thread)32. Long expander iever

33. Short expander lever34. Washer35. Expander lever nut36. Cable pin37. Spring clip^38. Dust cover39. Washer40. Expander bush ing4 1 . Pivot pin42. Pivot pin/torque stop pin43. Nut44. Bolt45. Tab washer46. Support plate47. Balance weight48. Balance weight

146 CHAPTER EIGHT

FRONT HUBDISC TYPE BRAKE

1. Rim and hub assembly2. Spindle nut3. Wheel spindle4. Left-side bearing5. Bearing lock ring6. Hub shell7. Spacer8. Right side bearing9. Spacer

10. Washer11. Seal12. Washer13. Rim14. Right-side inner spoke15. Right-side outer spoke16. Left-side inner spoke17. Left-side outer spoke18. Right-side spoke nipple19. Left-side spoke nipple

20. Dust cover21. Right-side spacer22. Disc23. Stud24. Nut25. Washer26. Caliper assembly27. Caliper28. Piston29. Seal30. Seal31. End plug32. Friction pads33. Bleed nipple34. Screw35. Spring washer36. Balance weight37. Balance weight


of the spacer to one side so the end of the driftcan be applied to the bearing race. Tap the bear-ing out slightly and move the drift to the oppositeside, moving the spacer so the drift can be ap-plied to the bearing, and tap the bearing out,continuing the procedure—from side-to-side—until the bearing has been driven out of the hub.

5. Remove the spacer tube from the hub anddrive the double-row bearing out to the right sideof the hub, along with the washers and seal.

6. Clean and dry the parts thoroughly. Rotatethe bearings by hand and check them for radialplay and roughness. Inspect the seals for damageor deterioration and replace any pieces that aredefective. Pack the bearings with grease.

7. Line up the left-side bearing (single-row)squarely with the bore in the hub and tap it intoplace, applying a drift only to the outer race.Install the spacer, seal, and lock ring. Tightenthe lock ring securely.

8. Install the spacer tube into the left-side bear-ing through the right side of the hub. Fill thearea between the spacer and the inside of thehub with grease.9. Line up the right-side bearing (double-row)squarely in the right bearing bore. Using the axleas a drift, drive the bearing into the hub until itcontacts the shoulder of the spacer.

10. Install the small washer, seal, large washer,and spacer in the right side of the hub and installthe wheel in the motorcycle as described earlier.

C H A P T E R N I N E

REAR WHEEL AND BRAKE

This chapter describes repair and mainte-nance of the rear wheel hub, sprocket, anddrum and disc brakes.

REAR WHEEL

The rear wheel can be removed without dis-turbing the brake, sprocket, or drive chain.

Removal (1970 and Earlier)

1. Support the rear of the motorcycle so thewheel clears the ground.

2. Disconnect the speedometer cable from thedrive unit (Figure 1).

3. Carefully pry the 3 rubber plugs out of theright side of the hub and unscrew the 3 sleevenuts (Figure 2).

4. Unscrew the axle and pull it out while liftingup on the rear wheel. The spacer tube and thespeedometer drive should fall clear as the axleis removed. Pull the hub away from the drum tothe right and remove wheel from motorcycle.

REAR WHEEL AND BRAKE 149

Removal (1971 through 1974)

1. Support the rear of the motorcycle so therear wheel clears the ground.

2. Unscrew the axle (Figure 3) and pull it outwhile lifting up on the rear wheel. The spacerand speedometer drive should fall clear as theaxle is removed.

A. Speedometer cableB. AxleC. Right-side spacerD. Speedometer drive

3. Pull the wheel to the right to release it fromthe drum and remove it to the rear.

Removal (1975 with Disc Brake)

1. Support the rear of the motorcycle so therear wheel clears the ground.2. Loosen the lower mounting bolt on the rightrear suspension unit (Figure 4) and push theunit as far to the left as the circUp on the boltwill allow.3. Unscrew the axle from the right side and pullit out while supporting the rear wheel. The rightside spacer will fall clear as the axle is removed.

4. Disconnect the brake caliper mount from theshock absorber mount and hang the caliper onthe hook beneath the seat rail (Figure 5); donot let the caliper hang on the brake line.

5. Pull the wheel to the right to release it fromthe sprocket and remove it to the rear.

Installation

Install the wheel by reversing the removalsteps. On early models, line up one of the mount-ing studs in the brake drum with the swing armso the bearing boss on the hub will pass between

150 CHAPTER NEVE

the other 2 studs. Then line up the studs withthe hole in the hub and push the wheel tothe left. On late models, line up the paddles onthe drum (on the sprocket on disc brake models)with the shock absorber holes or slots in thewheel and push the wheel to the left.

On drum brake models, set the speedometerdrive in place so that the tangs in the drive gearare engaged with the slots in the bearing lockring (Figure 6).

Hold the spacer in place between the swingingarm and the speedometer drive and start the axlein through the arm. Push it all the way in andtighten it securely.

REAR HUB

Three hub types are used on Norton twins.On the early drum brake hub, through 1970(Figure 7), the brake drum and drive sprocketbolt to the hub. On the later drum brake hub,1971 on (Figure 8), 3 plastic shock absorberelements in the hub engage 3 paddles in thebrake drum. In the disc brake hub, 1975 models(Figure 9), 5 paddles in the sprocket engage 5rubber blocks located in the drive center inthe hub.

With all types, the rear wheel can be removedwithout disturbing the brake, sprocket, or drivechain. For major service such as repacking orreplacing the bearings, however, the entire as-sembly must be removed from the swinging arm.The recommended service interval for bearingsis every 10,000-12,000 miles. The bearings andbrake components should be inspected duringeach service and replaced as required.

The early and late drum brake wheels differinternally only in that the early wheel does nothave a bearing in the brake drum. Instead, ithas a double-row ball bearing assembly in thebrake side of the hub and a single-row ball in theright side. The late wheel has a double-row ballassembly in the brake drum and a single-rowball assembly at each side of the hub. The pro-cedure for removing the bearings from the hubis the same for both types.

REAR HUB —1961-1970


REAR HUB—197M974

DisassemMy (Drum Brake Hubs)

1. Unscrew the lock ring from the right side ofthe hub (Figure 10). This piece has a left-handthread. A drift or punch should not be used tobreak the ring loose. Instead, use either Nortontool No. 063965 or make a wrench from Vs in.wall tube or pipe like the one shown inFigure 11.2. Remove the felt washer and spacer from thehub. Put a washer and the large right-side spaceron the rear axle. Insert the axle into the hubfrom the left side (Figure 12). Drive the axle

152 CHAPTER NINE

3334

22

REAR WHEEL AND HUB(1975)

1. Wheel assembly2. Hub3. Rim4. Spoke, right hand5. Spoke, left hand inner6. Spoke, left hand outer7. Spoke nipple8. Bearing sleeve9. Bearing

10. Bearing11. Sprocket bearing spacer12. Nut13. Washer14. Stud15. Disc16. Drive center17. Plate18. Lock ring

19. Drive rubber20. Drive rubber21. Oil seal22. Sprocket23. Ball journal bearing24. Circlip25. Oil seal26. Dummy shaft27. Washer

28. Axle nut29. Axle assembly30. Seal sleeve31. Speedometer gearbox32. Washer33. Balance weight34. Balance weight35. Security bolt


into the hub with a soft mallet until the bearingcontacts the machined stop. This pushes theright-side bearing partially out of the hub.Remove the rear axle.

3. Drive the spacer out of the brake-side bearingusing a shouldered drift that will pass throughthe bearing inner race. This drives the right-sidebearing out of the hub. If a suitable drift is notavailable, the front axle can be used; however,make sure that the front of the frame is sup-ported before removing the axle from thefront wheel.

4. Insert the rear axle and large spacer into thebrake-side bearing from the right end of the huband drive the bearing out.

5. On late wheels, remove the drum from thebrake assembly and remove the spacer, washers,and circlip from the right side of the drum(Figure 13). Screw the axle nut onto the left endof the short axle and drive the bearing out of thedrum to the right using a soft mallet.

Disassembly (Disc Brake Hub)

1. Remove the wheel as described earlier. Un-screw the nut from the end of the dummy axle(Figure 9) and withdraw the axle from thesprocket. Collect the washer and disengage thesprocket from the chain. Pull the speedometerdrive free of the sprocket.

2. Remove the bearing spacer, the seal, and thecirclip from the sprocket. Insert the dummy axleinto the bearing and knock it out by tapping onthe dummy axle with a soft mallet.

3. Unscrew the nuts which attach the disc tothe hub and remove the lockwashers, spacer, andoil seal. From the other side of the hub, unscrewthe bearing lock ring and remove the drivecenter.

4. With the dummy axle, drive the bearingspacer into the hub from the drive side. Thiswill knock the opposite bearing out of the hubtoward the brake side. Then, invert the hub andusing the dummy axle with the long axle screwedinto it, knock out the drive side bearing.

Inspection

Thoroughly clean and dry all parts, includingthe inside of the hub and drum. Rotate bearingsby hand and check for roughness and axial play.Inspect metal parts for corrosion. If there is anydoubt about a bearing's condition, replace it.Replace the felt seals.

Assembly (Drum Brake Hubs)

L Pack the bearings with a good grade ofbearing grease.

2. Line up the right-side hub bearing (single-row) with the bearing bore and tap it in evenlyfar enough to permit the spacer, felt washer, andlock ring to be installed. Tighten the lock ring(left-hand thread) securely.

3. Tap the bearing spacer tube into the right-side bearing from the left. On 1970 and earlier

154 CHAPTER NINE

RIM AND HUBASSEMBLY

1. Hub assembly2. Wheel axle3. Wheel axle nut4. Axle spacer5. Speedometer gearbox6. Washer7. Nut8. Brake cam9. Torque stop pin

10. Torque stop pin nut11. Bolt12. Cam bearing nut13. Cover plate assembled14. Cover plate outer spacer15. Bearing cam and stay16. Lever return spring17. Brake shoe

17A. Brake shoe slipper18. Plate19. Washer20. Lever21. Washer22. Spring23. Left-side bearing spacer24. Thick cush drive buffer25. Thin cush drive buffer26. Bearing27. Lock ring28. Hub shell29. Inner bearing spacer30. Felt retaining washer31. Spacer32. Dished washer33. Seal34. Gearbox spacer

35. Spindle washer36. Disc screw37. Security bolt38. Rim39. Spoke40. Left side inner spoke

40A. Right-side inner spoke41. Nipple42. Rear hub disc43. Brake drum44. Dummy axle45. Felt retaining washer46. Felt seal47. Circlip48. Bearing49. Balance weight50. Balance weight


models, the distance between the end of thespacer and the shoulder is greater on the left(brake) side ±an on the right to accommodatethe wider double-row bearing in the left side ofthe hub. Make certain that the shorter end of thespacer is installed in the right-side (single-row)bearing.

4. Set the left-side bearing squarely in the leftside of the hub and tap it evenly around theouter race until it is stopped by the shoulder onthe spacer tube. Don't apply any pressing ortapping force to the bearing inner race.

5. Install the felt washer and seal and the outermetal washer. On early wheels, the outer washermay be tapped in with a small punch or drift.

6. On late wheels, install the washer and shortaxle in the drum, followed by the felt seal andthe felt retainer. Line up the double-row bearmgsquarely with the bearing bore in the drum andtap it evenly around the outer race until its outeredge is beneath the circlip groove. Install thecirclip with the outer edge facing outward andmake certain it's completely seated in thegroove. Install the inner felt retainer, the feltseal, the dished washer, the outer felt retainer,and the bearing spacer.

NOTE: An improved bearing spacerfor Commando models up to engineNo. 305427 can be purchased throughNorton dealers as a standard replace-ment item. The new spacer (partNo. 065290) replaces spacer No.062070 and is interchangeable withoutany modifications.

SPROCKET AND BRAKEASSEMBLY

Removal/Installation

1. Remove the wheel as described earlier.

2. Remove the master link from the rear chainand remove the chain from the rear sprocket.Unplug the electrical leads from the brake lightswitch (Figure 14).3. Disconnect the rear brake cable from thebrake cam arm (Figure 15).4. Unscrew left axle nut and remove the brakeand sprocket assembly from the swinging arm.


REAR DRUM BRAKE

There is no specified interval for replacing thebrake linings; the rate of wear varies greatly de-pending upon riding habits. The linings shouldbe caref uUy examined each time the wheel bear-ings are serviced. If the lining is worn down toor near the rivet heads, the complete shoes andlinings should be replaced. If these are not avail-able, the existing shoes can be relined and thenew linings arced to fit the drums. This is a jobfor a specialist and should not be attempted bya hobbyist mechanic.

Removal and Disassembly

1. Remove the rear wheel and sprocket/brakeassembly as described earlier.

156 CHAPTER NINE

2. Remove the springs by lightly gripping thecoil section with a conventional pair of pliersand extending one of the spring ends withneedle-nose pliers (figure 16).

3. Straighten the tab washers and unscrew the 2nuts from the shoe pivots. Remove the shoesfrom the brake backing plate.

4. Unscrew the nut from the end of the cam-shaft (Figure 17) and remove the lever. Pull thecam out of the backing plate. It is not necessaryto remove the cam bearing and stay unless thebearing bore is badly worn and must be replaced.

Inspection

Thoroughly clean and dry all parts except thelinings. Check the contact surface of the drumfor scoring. If there are grooves deep enough tosnag a fingernail, the drum should be trued by abrake specialist. In such case, the linings will

have to be replaced and the new ones arced lothe new drum contour.

Check the linings for wear as described above.If they are serviceable, inspect them for im-bedded foreign material. Dirt can be removedwith a stiff wire brush, but if they are soakedwith oil or grease they will have to be replaced.

Inspect the cam lobes and the pivot area ofthe shaft for wear and galling. Minor roughnesscan be removed with emery cloth but if eitherarea is deeply scored or severely worn, the camshould be replaced.

Assembly

1. Grease the cam bearing bore, the cam pivotarea and lobes, and the pivot pins with high-temperature grease. Apply only a light coat toeach of these points; excess grease is likely tofind its way onto the linings and render themunserviceable.

2. Install the cam in the plate. Install the shoeson the pivot pins and against the cam. If theshoes have detachable slippers, make sure theseare located between the cam and the ends ofthe shoes.

3. Install the tie plate, the tab washer plate, andthe pivot bolts. Tighten the bolts securely andbend the tab washers over against the fiats.

4. Install the return springs between the shoes.Use a short wire loop and screwdriver to stretchthe springs over the ears on the shoes.

5. Reinstall the brake, sprocket, and rear wheelas described earlier. Before tightening the axlenut, connect the cable to the brake arm andapply the brake fully to centralize it in the drum.Hold the brake on and tighten the axle nut.

REAR DISC BRAKE

The rear disc brake is actuated by hydraulicfiuid and is controlled by a foot lever like thedrum-type brake. Unlike the drum brake, how-ever, the disc brake does not require adjustment.

It's essential that the work area and all toolsbe scrupulously clean when doing any majorservice on the hydraulic system. Tiny particlesof foreign matter and grit in the caliper assemblyor the master cylinder can damage the com-ponents making the system unsafe and requiring


replacement of damaged parts. Also, sharp toolsmust not be used inside the caliper or on thepistons. If there is any doubt about your abilityto correctly and safely carry out major service onthe brake components, take the job to a Nortonservice shop or a brake specialist.

Master CylinderRemoval and Disassembly

1. Unscrew the bolt which attaches the brakeunion to the right foot peg plate (Figure 18).Note the position of the ground wire so it maybe reinstalled in the same location.

2. Slightly loosen the Allen screws which attachthe master cylinder to the foot peg stalk(Figure 19). Depress the kickstarter and blockit or tie it down so it is out of the way. As analternative, the kickstarter pedal may be re-moved. Unscrew the 3 bolts which attach thefoot peg stalk to the plate. Swing the stalk outfar enough to gain access to the brake line unionin the end of the master cylinder and unscrewit. It is a good idea to place a drip pan beneaththe cylinder to catch brake fluid when the unionis disconnected.

3. Loosen the forward locknut on the brake rod(Figure 20) and remove the cotter key from thepin which attaches the clevis to the brake pedal.Remove the pin and disconnect the clevis from

the brake pedal. Unscrew the clevis from thebrake rod. Unscrew the Allen screws whichattach the master cylinder to the foot peg stalkand remove the cylinder.4. Refer to Chapter Eight, Front Disc Brake,for disassembly, inspection, assembly, andbleeding procedures.

Brake Pad Replacement

Brake pad replacement for the rear wheelcaliper is identical to that for the front. Referto Chapter Eight.

Caliper Rebuilding

Refer to Chapter Eight for caliper rebuildinginstructions.

C H A P T E R TEN

FRAME, SUSPENSION, AND STEERING

Included in this chapter are service, mainte-nance, and repair procedures for all chassiscomponents such as frame, front suspension,rear suspension and swinging arm, and theTsolastic system.

FRAME

Frame service is limited to inspection forcracks in welds and tubes and restoration of thepaint. If bending damage is suspected or appar-ent, the frame should be inspected and repairedby an authorized Norton service shop or bya specialist experienced in frame repair. Figure 1and Figure 2 are provided as reference for in-spection and repair.

ISOLASTIC ENGINE MOUNTS

One of the Norton Commando's key featuresis its Tsolastic system. The entire power trainfastens to the rest of the motorcycle with resil-ient mounts, thereby preventing normal but stillbothersome drive train vibrations from affectingthe rider and the controls. The Isolastic mountsmust be inspected and adjusted occasionally,and need to be removed and serviced only afterlong use.

Inspection

1. Peel back the rubber cover on the left side ofthe Tsolastic mount.

2. Push the engine (front mount) or rear wheel(rear mount) to the right to take up the slack inthe mount and measure the clearance betweenthe plated collar and the plastic washer (Fig-ure 3). Clearance should be 0.010 in. (0.25mm).

Front Mount Adjustment(750 and 850 Mark II Models)

1. Unscrew the nut from the left side of thefront mount (Figure 4). Line up one of the flatson the right end of the bolt so it will clear theengine case (Figure 5).

FRAME, SUSPENSION, AND STEERING 159

"it-) V^ ~ s

9.45 in. I240.0mm \

7.45 in.UIao

I

oCO

160 CHAPTER TEN

240.0mm

189.2mm

274.32mm

EEr-.

s

ao

oin00I

CO

Ul

a


2. With a soft drift, drive the bolt into themount from the left side far enough so that therubber cover, spacer, and plastic washer can beremoved. Remove the tube cap and the shim(Figure 6).

3. Tnstall shim(s) of appropriate thickness.Shims are available in thicknesses of 0.005,0.010, 0.020, and 0.030 in. Use as few shims aspossible; for instance, use one 0.030-in. shimrather than three 0.010-in. shims.

Example: Actual clearanceDesired clearanceDifference to be

compensated

Existing shim

0.040 m0.010 in

0.030 in

0.010 in

In this instance, discard the 0.010 in. shimand substitute a 0.030 in. shim.

4. Replace the plastic washer if it shows wear.

5. Reassemble the pieces in order—shims, tubecover, plastic washer, spacer, and rubber cover.Gently tap the bolt in from the right while align-ing the pieces. Screw on the nut and tighten itto 25 ft.-lb. (3.456 mkg).

Rear Mount Adjustment(750 and 850 Mark II Models)

1. Unscrew the nut from the right end of themounting bolt (Figure 7).

2. With a soft drift, drive the bolt into themount from the right side until it protrudesabout 4 inches on the left side.

3. Peel the rubber cover off the tube and pushit down and back. Remove the cover, spacer,and plastic washer. Remove tube cap and shim.

4. Install shim(s) of appropriate thickness (seeexample above). Replace the plastic washer if itshows signs of wear. Clean the parts thoroughlyand lubricate them with a light coat of siliconegrease.

162 CHAPTER TEN

5. Install the shims and cap on the mountingtube. If more than one shim is required, thethinner shim should be outboard, against thecap. Assemble the rubber cover, spacer, andplastic washer together. Peel back the lip on thecover so that the assembly can be fitted betweenthe mounting tube and the frame plate. It may benecessary to have someone push the rear wheelto the left to provide sufficient clearance. Therubber cover must fit completely over the endcap and the tube, and the spacer, washer, andcap should turn freely when the cap is turned.

6. With assistance, line up mounting bolt withmounting hole in the frame and carefully drivebolt in from the left side. Be sure to reinstall thespacer between the frame mounting bracket andthe footrest plate. Install the fiat washer and thenut. Tighten the nut to 25 ft.-lb. (3.456 mkg).

Front and Rear Mount Adjustment(850 Mark III Models)

The Isolastic mounts on 850 Mark III modelsare equipped with threaded adjusters and adjust-ment does not require the addition or removalof shims.

1. Loosen the nut on the end of the mount andpeel the rubber cover away from the adjuster.Remove the spring clip (Figure 8).

2. Insert a 0.010 in. (0.25mm) flat feeler gaugein the mount between the thrust washer and theend cap (Figure 9) and turn the adjuster untilthere is a slight drag on the feeler gauge when itis removed. Then, without turning the adjusterfurther, tighten the end nut on the mount andinstall the spring clip and refit the rubber cover.Repeat this procedure for the remainingmount.

Front Mount Removal

In time, the Isolastic mounts require removal,cleaning, replacement of worn parts, installation,and adjustment. However, this service is notroutine and is rarely required before manythousands of miles. If the Isolastic units must berebuilt to the extent that the rubber bushings areto be replaced, a special installation tool is re-quired (Norton tool No. 063971). If you do nothave access to this tool, the bushings must bereplaced by a Norton service shop after theIsolastic mounts have been removed from themotorcycle. Refer to Figure 10 for the followingprocedure.

NOTE: Construction of the Isolasticunits on 850 Mark III models is suchthat they require a press to removethem from the mounts. This should beentrusted to a Norton dealer. Removalof the mounts is essentially the same asfor the earlier mounts. Adjustment isdescribed above.

1. Remove the right-side exhaust pipe and un-screw the nut from the left end of the frontmounting bolt.


2. Line up one of the flats on the head of themounting bolt so that it will clear the enginecase (Figure 5) and drive the bolt out to theright side with a soft drift. The front of the en-gine should be supported so that the bolt threadswill not be damaged by frame mounting platesas the bolt is drifted out.

3. Peel back the left-side rubber cover and re-move it along with the spacer and plastic washer.Do the same to the right-side cover. Remove thetube caps and shims from both sides.

4. Unscrew 2 nuts and bolts which attach themount to the engine (Figure 11). Remove themount.

5. Insert the end of a drift about V2 inch intothe sleeve of one of the bushings (Figure 12).Using the drift as a lever, turn the bushing in thetube (Figure 13) so it can be easily removed.

Rear Mount Removal

1. Remove the engine from the motorcycle.Refer to Chapter Four.2. Remove the end bushings in the same manneras for the front mount. Remove the spacer tubesand buffers from each end of the mounting tube.3. Set the end of a drift against one side of thecenter bushing and tap the drift with a hammerto tum the bushing in the mounting tube so itcan be easily removed.

Front Mount Assembly(750 and 850 Mark II)

L Place the tapered bushing guide (Norton toolNo. 063971) over the end of the mounting tube(Figure 14). Coat the circumference of one ofthe bushings with rubber lubricant (e.g., glyc-erine) and press it evenly into the guide.

6. Remove the spacer and rubber buffers fromthe mounting tube. Remove the opposite bushingin the same manner as the first.

2. Set the driver in place on the bushing(Figure 15) and press it into the mounting tubeuntil the driver bottoms on the bushing guide.

164 CHAPTER TEN


ENGINE MOUNT

1.2.3.4.5.6.7.8.9.

10.11,12.13.14.15.16.17.18.19.20.21.22.23.24.25.26.27.28.29.30.31.32.33.34.35.36.37.38.39,40.41.42,43.44.45.46.47,48.49.50,51.52.53.54.55.

Engine steadyEngine steady to iiead screwEngine steady screw washerEngine steady side-plateEngine steady spacerEngine steady rubber mountingEngine steady studEngine steady stud washerEngine steady stud nutFront engine mountingFront engine plate boltFront engine plate washerEngine front plate nutFront engine plate bolt to frameFront engine plate bolt washerFront engine plate bolt nutFront engine mounting bushingFront engine mounting spacerFront engine mounting bufferFront engine mounting tube capFront engine mounting shim .005 in.Front engine mounting shim .010 in.Front engine mounting shim .020 in.Front engine mounting shim .030 in.Front engine mounting collarFront engine mounting washer (PTFE.)Front engine mounting gaiterRear engine mountingRear engine plate boltRear engine plate washerRear engine plate nutRear engine plate bolt bottomRear engine piate washerRear engine plate nutRear engine mounting rubberRear engine mounting spacerRear engine mounting bufferRear engine mounting tube capRear engine mounting shim .005 in.Rear engine mounting shim .010 in.Rear engine mounting shim .020 in.Rear engine mounting shim .030 in.Rear engine mounting collarRear engine mounting washer (PTFE,)Rear engine mounting gaiterCirclip for isolastic buffersRear engine mounting studCenter stand (750 only)Center stand springCenter stand boltCenter stand washerCenter stand nutCenter stand spacer (750 only)Center stand (850 only)Center stand spacer (850 only)

3. Install the buffers and circlips on the spacerlube (Figure 16), turn the mounting tube over,and set the buffer assembly in place so that thetube rests on the bushing that has been installed.

4. Install the second bushing in the same man-ner as the first, using the guide and driver.

Rear Mount Assembly(750 and 850 Mark II)

1. Coat the circumference of the center bushingwith rubber lubricant and press it into themounting tube by hand, using a length of tubingor pipe as a driver. The bushing must be centeredin the tube, 3Vi in. (82mm) from each end.

2. Install the buffer and circlips on one of thespacer tubes. Set it in place in the mounting tube.

166 CHAPTER TEN

3. Coat the circumference of one of the outerbushings with rubber lubricant and press it intothe mounting tube until it is stopped againstthe spacer.

4. Turn the mounting tube over and install theother buffer and tube assembly and the outerbushing in the manner just described.

Front and Rear Mount Installation

Reinstall the mount and engine/transmissionpackage by reversing the removal steps. Installnew Isolastic mounts on the cylinder headsteadyand check and adjust the clearance of the frontand rear mounts as described earlier.

FRONT SUSPENSION

The Norton front suspension consists of aspring-controlled, hydraulically dampened tele-scopic fork. Before suspecting major trouble,drain the fork oil and refill with proper type andquantity. See Chapter Four. Tf you still havetrouble, such as poor dampening, tendency tobottom out or top out, or leakage around rubberseals, then follow the service procedures inthis section.

To simplify fork service and to prevent themixing of parts, the legs should be removed,serviced, and reinstalled individually.

Removal

1. On models equipped with a front disc-brake,the caliper can be removed with the brake lineattached to eliminate the need for refilling andbleeding the system. Remove the nuts whichhold the brake line bracket to the right forkleg (Figure 17). Remove the bolts which holdthe caliper to the fork leg and pull ± e caliperaway from the disc. Insert a block, such as apiece of tubing, between the brake pads to pre-vent them from being ejected (Figure 18) byaccidental movement of the brake lever. Suspendthe caliper from the end of the right handlebarwith a piece of cord so that it is out of the way.Be careful not to bend the brake line too sharply.As a precaution against damaging the caliper,the fuel tank, or the engine cooling fins, wrapseveral thicknesses of newspaper around thecaliper and tape it in place.

2. Block up the front of the motorcycle to liftthe front wheel off the ground.

3. On models with a drum-type front brake,disconnect the brake cable from the lower brakearm by removing the clevis pin (Figure 19).Unscrew the cable adjuster from the boss on thebrake backing plate.4. On all models, unscrew the axle nut (Fig-ure 20). Loosen the pinch bolt at the bottom ofthe left leg (Figure 21). Tnsert the shaft of ascrewdriver or small bar through the hole in theleft end of the axle and pull it out of the forks


and wheel while supporting the weight of thewheel.

5. Unscrew the 4 bolts that hold the fenderstruts to the bottom of the fork legs, and theremaining 2 nuts that hold the center stay tothe aluminum fork slider (Figure 22). Removethe fender and set it aside.

6. Unscrew the cable collars from the tachom-eter and speedometer and unplug the instrumentlamp lead from the wiring harness.

7. Unscrew the caps from the tops of the forks(Figure 23). Hold the damper locknut with awrench and unscrew the cap from the top of thedamper rod (Figure 24). Remove the instru-ments and set them aside.

8. If the motorcycle is equipped with forkgaiters, loosen the upper clamps. Loosen thepinch bolts in the bottom fork yoke (Figure 25).Screw one of the caps several complete turnsinto the top of the fork to be removed and tapit sharply with a soft mallet to break the tubeloose from the yoke (Figure 26). Remove thecap once again and pull the fork leg down andout of the yokes.

168 CHAPTER TEN

Disassembly

1. Invert the fork leg over a drip pan and pourout the oil. Clamp the lower end of the fork legin a vise with the leg positioned vertically.Wooden blocks or soft jaw pads should be usedbetween the vise jaws and the fork leg to pre-vent damage.

2. Peel the dust cover away from the slider andmove it up the tube (Figure 27). If the motor-cycle is equipped with fork gaiters, loosen thebottom clamps and slide the gaiters off the tubes.

FRONT FORKS

1. Right leg assembly (drum braite)2. Right slider (drum brake)3. Right leg assembly (disc brake)4. Right slider (disc brake)5. Left leg assembly (drum brake)6. Left slider (drum brake)7. Left leg assembly (disc brake)8. Left slider (disc brake)9. Pinch bolt (drum only)

10. Gaiter11. Collar12. Washer13. Damper rod seat14. Damper rod15. Damper rod cap nut16. Damper rod locknut17. Slider drain plug18. Damper tube anchor bolt19. Damper tube cap20. Damper tube21. Damper valve22. Damper valve stop pin23. Fork spring24. Fork spring locating bushing25. Damper tube anchor bolt washer26. Damper tube anchor bolt washer27. Main tube28. Fork tube bushing circlip29. Fork tube bushing30. Oil seal31. Oil seal washer32. Fork tube guide bushing33. Fork tube top bolt34. Washer35. Stud36. Washer37. Nut38. Steering head bearing39. Bearing spacer40. Washer41. Cover42. Washer43. Nut44. Socket screw45. Lower yoke (750 only)

45A. Lower yoke (850 only)46. Plug for lower yoke47. Upper yoke with stem (750 only)

47A. Upper yoke with stem (850 only)48. Stem blanking plug49. Clip50. Screw51. Lock/keys52. Right headlight bracket/top cover53. Left headlight bracket/top cover54. 0 ring55. Bolt56. Washer57. Nut

170 CHAPTER TEN

Unscrew the collar from the top of the sliderand pull up on the leg to remove it from theslider.3. Unscrew the bottom bolt from the slider andpull out the spring and damper assembly.

4. Lightly clamp the damper tube in a vise andunscrew the cap. Pull out the damper rod, clampit in the vise and remove the locknut, washer,and valve. Remove the valve stop pin.

5. Remove the circlip and steel bushing fromthe end of the fork tube.

Inspection

Thoroughly clean and dry all parts. Checkthe bushings and the fork tube for signs of wearor galling. Check the damper rod for bending byrolling it on a fiat surface. Carefully check thedamper valve and the stop pin for wear or dam-age. Inspect the seals for scoring and nicks andloss of resiliency. If there is any doubt abouttheir condition, pry them out and press in newseals using a large socket as a driver.

Any parts that are worn or damaged shouldbe replaced; simply cleaning and reinstalling

unserviceable pieces will not improve perform-ance of the front suspension.

Reassembly

Refer to Figure 27 and reassemble the forkleg components in reverse order of disassembly.When the damper assembly has been assembledand installed in the slider, oil the outside of theupper fork tube and fit it into the slider. Installthe collar in the top of the slider and tighten itsecurely by hand. Slide the rubber dust coverdown over the top of the slider.

Installation

Slide the assembled fork leg up into the loweryoke, through the headlight bracket tube, andinto the top yoke. Install the instrument caseand fork cap and tighten the cap to draw thefork tube up into the taper in the top yoke.Whenthe fork tube is firmly seated in the yoke, tightenthe pinch bolt in the lower yoke and unscrewthe top cap.

Refer to Chapter Two. Fill the fork legs withthe correct amount and grade of oil. Reconnectthe top cap to the damper tube rod and securelytighten the locknut. Screw the top cap into thetube and tighten it to 40 ft.-lb. (5.83 mkg).

Reassemble the rest of the components inreverse order of disassembly. On front disc brakemodels, make certain that there is sufficientoperating pressure by pumping the lever severaltimes before riding the motorcycle.

STEERING

Service to the steering consists of periodicallychecking and correcting the tightness of thestem (1970 and earlier models) and replacingthe bearings.

Adjustment (1970 and Earlier)

1. Block up the front of the motorcycle so thewheel is off the ground. Take hold of the lowerfork legs and try to move them back and forth.If any movement can be felt, the steering headmust be tightened.

2. Unscrew 4 Allen bolts from the handlebarretainers (Figure 28) and remove the handlebars.


The handlebars can be rested on the fuel tank,but the tank should first be covered with a cleancloth to prevent the handlebars from damagingthe paint.

3. Loosen the cap nut on the steering stem andpinch bolts in the lower fork yoke.

4. Tighten the stem adjuster nut, turning it onefiat at a time while checking the movement ofthe forks from lock-to-lock and as describedin Step 1.

When correctly adjusted, the forks shouldturn freely from lock-to-lock and there shouldbe no apparent back-and-forth movement of thefork assembly in the steering head.

WARNING// the steering head is adjusted tootight, the front end will tend to bindunder load, creating a hazardous con-dition.

5. When the adjustment is correct, retighten thetop stem nut and the pinch bolts, and reinstallthe handlebars.

Disassembly (1970 and Earlier)

1. Remove the fork legs and handlebars as de-scribed earlier. Unscrew the stem cap nut andtap the top yoke up and off the stem with asoft mallet.

2. Unscrew the stem adjuster nut and removethe dust cover. Tap the stem and bottom yokedown and out of the bearings.

3. Carefully drive the bearing assemblies out ofthe steering head—first the bottom bearing, then

the top. Apply the end of the drift to the innerrace of each bearing.

Disassembly (1971 and Later)

1. Straighten the tab washer on the bottom stemnut and unscrew the nut (Figure 29).

2. Take hold of the headlight and tap the bottomyoke down and off the stem with a soft mallet.Remove the O-rings from each of the headlightbracket tubes (2 on the bottom and one on thetop). To prevent damage to the headlight, wrapseveral thicknesses of newspaper around it andtape them in place.

3. Drive the stem and top yoke upward with asoft mallet and remove the assembly from thesteering head along with the dust cover andwasher.4. Tnsert a drift through the inner race of thetop bearing and push the interior spacer tubeto the side so the end of the drift can be appliedto the inner race of the bottom bearing. Care-fully tap the bearing out of the steering head andremove the spacer. Remove the top bearing bydriving it upward from the bottom. Again, applythe drift to the inner race.

Inspection

Thoroughly clean and dry the bearings andthe inside of the steering head. Rotate the bear-ings by hand and check for roughness and radialplay. If there is any doubt about their condition,they should be replaced.

172 CHAPTER TEN

Assembly (1970 and Earlier)

1. Lightly oil the outer race of one of the bear-ings and fit it squarely into the bottom of thesteering head. Tap it all the way in with a softmallet until it bottoms on the machined lip insidethe head. Then install the top bearing in thesame manner.

2. Insert the stem into the bearings from thebottom. Set dust cover over the top of stem.

3. Screw on the stem nut and tighten it until nomovement can be felt in the yokes but they willstill turn freely from lock-to-lock.

4. Position the headlight and brackets on thebottom yoke and set the top yoke in place. Installthe washer and acorn nut on top of the yoke butdo not tighten it.

5. Install the fork legs as described earlier.When the tops of the fork legs are correctlyseated in the tapers in the top yoke, adjust thestem nut as described under Adjustment (1970and Earlier),

6. Reassemble the remaining components asdescribed earlier.

Assembly (1971 and Later)

1. Lightly oil the outer race of one of the bear-ings and fit it squarely into the bottom of thesteering head.

2. Refer to Figure 27 and set the spacer intothe top of the steering head.

3. Oil the outer race of the top bearing and fitit squarely into the top of the steering head. Thebearings are pressed in by the yokes as the stemnut is tightened.

4. Install the washer and dust cover on the topof the steering head. Tap the stem and top yokedown into the bearings with a soft mallet.5. Grease 2 of the 0-rings and set them in placeon the underside of the top yoke. Grease the re-maining 4 O-rings and set them in the recessesin the bottom yoke.

6. Hold the headlight and bracket tubes in posi-tion and line up the tops of the tubes with thetop yoke. Line up the bottom yoke with the bot-toms of the bracke ttubes and the stem, and pushit up into place.

7. Set the tab washer in place and screw on the

bottom stem nut while checking the alignmentof the bracket tubes with the yokes. Tighten thenut only enough to pull bottom yoke into place.

8. Install the fork legs as described earlier.When the tops of the fork legs are correctlyseated in the tapers in the top yoke, tighten thestem nut and then the pinch bolts in the bottomyoke. Bend the tab washer over against one ofthe fiats on the stem nut.

9. Reassemble the remaining components asdescribed earlier.

REAR SUSPENSION

The rear suspension units are spring con-trolled and hydraulically damped. Spring pre-load can be adjusted by rotating the cam ringsat the base of the springs—clockwise to increasepreload, counterclockwise to decrease it. Bothcams must be indexed on the same detent. Thedamper units are sealed and cannot be rebuilt.Service is limited to removal and replacement ofeither an entire unit or the damper alone afterthe spring has been removed.

Removal

Removal and installation of the rear suspen-sion units is easier if they are done separately.The remaining unit will support the rear of themotorcycle and maintain the correct relationshipbetween the top and bottom mounts.1. Unscrew the bottom nut and bolt whichattach the suspension unit to the swinging arm(Figure 30).


NOTE: On 850 Mark HI models, re-move the circUp from the lower rightbolt before removing the bolt.

2. Remove the seat and unscrew the knob farenough to expose the top suspension nut so itcan be turned with a wrench (Figure 31). Pullthe suspension unit out of the top mount.

Disassembly

1. Clamp the lower mounting eye in a vise androtate the preload cam to its softest position.2. With assistance, compress the top spring andremove the 2 keeper segments (Figure 32). Re-move the spring from the damper.

Reassembly and Installation

Reassemble and install the suspension unit byreversing the steps above.

SWINGING ARM

Under normal use and with correct periodiclubrication, the swinging arm bushings have along service life. However, in time the bushingswill wear and must be replaced. Indications ofexcessive bushing wear are imprecise steering,and a tendency for the motorcycle to pull toone side or the other during acceleration andbraking.

Removal

1. Block up the motorcycle so the rear wheel isclear of the ground. Disconnect the rear chainand remove it from the wheel sprocket. Leave itin place on the countershaft sprocket to simplifyinstallation later on. Refer to the section on therear wheel and brake in this chapter and removethe wheel from the swinging arm.

2. On 750 and 850 Mark II models, place a drippan beneath the right end of the swinging armpivot and remove the long screw, end cap, andwashers from the arm (Figure 33). Allow theoil to drain.

3. Remove the entire right footrest assembly,noting the location of the ground lead for thezener diode (Figure 34).4. Disconnect the chain oiler on the swingingarm (Figure 35) and remove the bottom boltsfrom the rear suspension units.

5. On 750 and 850 Mark II models, remove thelock bolt from the center of the swinging arm

174 CHAPTER TEN

spindle (Figure 36). Remove the main frontmounting bolt from the engine and screw thenut all the way down on the threads. Screw thebolt into the end of the pivot tube and tightenthe nut to lock it in place. Slowly twist the boltand pull the spindle out (Figure 37). Removethe swinging arm, left cover, O-rings, andbearings (Figure 38).

6. On 850 Mark TTI models, unscrew the nutsfrom the pivot lock pins, remove the rubber capsfrom the pin bosses, and tap the pins upward tobreak them loose, using a soft mallet (Fig-ure 39). Remove pins. Referring to Figure 40,drill a hole in each of the swinging arm end capsand pry out the caps and discard them. Remove

the felt wicks from both sides and carefully tapout the pivot using a soft drift.

Inspection

Thoroughly clean and dry all parts. Slide thepivot bolt back into the swinging arm and checkfor radial play. Tf any play can be felt, the bush-ings and O-rings, and possibly the pivot bolt,should be replaced.


Bushing Replacement(750 and 850 Mark II)

1. Remove the outer O-rings and press the bush-ings out of the arm.

2. Install the dust covers on the bushings andpress them into the arm.3. Fit the large O-rings into the dust coversand the small O-rings into the outer recessesaround the bushings.

Bushing Replacement(850 Mark in>

1. Press the bushings out of the arm.

2. Install new seals on new bushings and pressthem into the arm, making sure they are squarelyseated in the bushing bores.

Installation (750 and 850 Mark II)

1. Oil the bushings. Lightly coat the inside faceof the left-end cap with grease, and set it in placeon the end of the arm pivot (Figure 41).2. Carefully move the swinging arm into place,taking care not to dislodge the left cap until the

176 CHAPTER TEN

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27

B.

SWINGiNG ARM, SUSPENSiON UNITS. CHAINGUARD-850 MARK III

1. Swinging arm2. Bearing3. Disc wick4. Seat assembly5. Welch plug6. Pivot spindle7. Washer8. Fiber washer9. Nut

10. Cotter11. Rubber plug12. Oil wick13. Chainguard14. Guard to swinging arm bolt15. Washer16. Nut17. Chainguard spacer18. Extension

19. Button20. Spring21. Chain adjuster22. Screw23. Nut24. Suspension unit25. Shock absorber26. Spring27. Collar

28. Top suspension unit bolt29. Washer30. Nut31. Bolt32. Bolt33. Washer34. Locknut35. Washer36. Caliper plate to bolt circlip

178 CHAPTER TEN

arm is in position and the cap is held by theprimary chaincase.

3. Oil the pivot spindle and push it into the armfrom the right side. Turn the bolt slowly as youapply pressure. Make sure that the arm is cor-rectly lined up and push the pivot spindle all theway in. Line up the pivot lock bolt hole with thehole in the mounting tube and screw in the bolt.Tighten it securely and unscrew the front enginemount bolt from the spindle. Then reinstall thebolt in the front engine mount.

4. Make sure the right-end O-ring is in placeand install the cap and lock bolt. Position thelubrication fitting on the cap so it is near the 12o'clock position (Figure 42) and tighten thebolt securely.

5. Reinstall the chain guard, the bottom sus-pension mounts, the rear wheel, and the chain,reversing the disassembly steps and referring tothe appropriate chapters where necessary. Re-connect the rear brake and adjust it. Adjust thefree-play of the chain. Fill the spindle with oilas described in Chapter Two.

Installation (850 Mark III)

1. Lightly coat the insides of the bushings withoil and set the swinging arm in place.

2. Oil the pivot spindle and start it into theswinging arm. Line up the spindle so that thelock slots are vertical, to the rear. Tap thespindle into the arm, being careful not to rotateit, using a soft mallet and finally a soft drift.When seated, the spindle ends should be equi-distant from the ends of the swinging armpivot tube.

3. Install the spindle lock pins with the taperedfiat facing forward. Tap the pins down into placewith a soft mallet to engage the notches in thespindle. Install the washers and screw on thenuts, drawing the pins down into place. Installthe rubber plugs in the lock pin bores.

4. Oil the felt wicks and install them in the arm.Install new end plugs, tapping them squarely intothe ends of the arm with a soft mallet.

5. Install the chain guard, bottom suspensionbolts, the rear wheel, brake caliper, and thechain, reversing the disassembly steps and re-ferring to the appropriate chapters where neces-sary. Do not forget the circlip on the bottomright suspension bolt. Adjust free-play of chain.

NOTE: On all models, refer to Chap-ter Seven, Zener Diode, and install thediode as described.

A P P E N D I X

SPECIFICATIONS

This chapter contains specifications for the NortonCommando models covered by this book. The tables arearranged in order of increasing engine displacement.Since there are differences between various models ofthe same engine displacement, be sure to consult thecorrect table for the motorcycle in question.

180 APPENDIX

750 COMMANDO

GENERAL

Displacement

Bore

Stroke

Maximum torqueStandardCombat

Compression ratioStandardCombat

CRANKSHAFT

Main bearing size (all)

Big end journal diameter

Permissible end float

CONNECTING RODS

Big end ID (less bearings)

Rod side clearance

Rod end clearance

PISTONS

Diameter (bottom of skirt) (standard)

Wrist pin diameter

Rings (type)

Ring end gapTop compressionSecond compression

CYLINDER BLOCK

Bore size

Grade A

Grade B

CYLINDER HEAD

Valve seat angle

CAMSHAFT

Bearing journal diameter

CAMSHAFT BUSHINGS

Fitted ID, left

Fitted ID, right

ROCKER SHAFT

Diameter

ENGINE

45 cu. in. (745cc)

2.875 in. (73mm)

3.503 in. (89mm)

48 ft.-lb. at 5,000 rpm49 ft.-lb. at 6,000 rpm

9 : 11 0 : 1

1,18 X 2.84 X 0.75 in, (30 x 72 x 19mm)

1.7505-1.7500 in, (44.462-44.450mm)

0.005-0.015 in. (0.127-0.381mm)

1,895-1.8955 in. (48.133 48.145mm)

0.013-0.016 in. (0.330-0,406mm)

Less than 0.001 in. (0.0254mm)

2.8712-2.8703 in. (72.931-72.906mm)

0-6869-0.6867 in. (17.447-17.442mm)

Two compression, one oil-control

0.010-0.012 in. (0.254-0,305mm)0.008 0.012 in. (0.203-0.305mm)

2.8746-2.8750 in. (72.959 72.969mm)

2.8750-2.8754 in. (72.969 72.979mm)

45-=

0,8735 in, (22.187mm)

0,8750 in. (22.225mm)

0,8750 in. (22,225mm)

0.4988-0.4985 in. (12,694-12.669mm)

(continued)

SPECIFICATIONS 181

75C) COMMANDO (continued)

VALVE TAPPET CLEARANCES (Engine Cold)

InletStandardCombat

ExhaustStandardCombat

VALVES

InletMead diameterStem diameter (plated area)

ExhaustHead diameterStem diameter (plated area)

VALVE GUrDES

Inside diameterOutside diameterWasher thickness

VALVE SPRINGS

Free lengthInnerOuter

Fitted lengthInlet inner

StandardCombat

Inlet outerStandardCombat

Exhaust innerExhaust outer

INTERMEDIATE TIMING GEAR

Bushing diameter (finished)Shaft diameter

CAMSHAFT CHAIN

SizeNumber of linksIdeal adjustment

IGNITION TIMING

Fully advanced position

CONTACT BREAKER

Point gap

0.006 in. (0.15mm)0.008 in. (0.2mm)

0,008 in. (0.2mm)0.010 in. (0.25mm)

1.490 in. (37.846mm)0.3115-0.3105 in. (7.912-7.886mm)

1.302 in. (33.0708mm)0.3115 0.3105 in. (7.912-7.886mm)

0.3145-0.3135 in. (7.988-7.962mm)0.5015-0.500 in. (12.738-12.725mm)0.062 in. (1.574mm)

1.482 in. (37.642mm)1.618 in. (41.097mm)

1.197 in. (30.40mm)1.259 in. (31.98mm)

1.259 in. (31.98mm)1.321 in. (33.55mm)1.222 in. (31.04mm)1.284 in. (32.61mm)

0.5627-0.5620 in. (14.292-14.274mm)0.5615-0.5610 in. (14.262-14.249mm)

0.375 in. x 0.225 (single-row, endless)38

3/16 in. (4.8mm) up and down on top run of chain

28° BTDC

0.014-0.016 in. (0.35-0.4mm)

(continued)

182 APPENDIX

SPARK PLUG

TypeGap

CARBURETORS

StandardTypeMain jet

1970

19711972

Needle jet197019711972

Needle position197019711972

Throttle valve (1970-1972)Combat

TypeMain jetNeedle jetNeedle positionThrottle valve

AIR FILTER

Type

RATIOS

Internal1st2nd3rd4th

OverallWith 19T gearbox sprocket(U.S. 1969-1972)

With 21T gearbox sprocket(U.S. and U.K. 1968)

With 22T gearbox sprocket(optional)

750

1st2nd3rd4th

1st2nd3rd4th

1st2nd3rd4th

COMMANDO (continued)

Champion N7Y or equivalent0.023-0.028 in. (0.59-0.72mm)

Two Amal concentric float 930 30mm

220 with early megaphone muffler210 with modified megaphone180 with restricted megaphone220220 (210 with mute)

0.1070,1060.106

MiddleMiddleMiddle (top with mute)3

Two Amal concentric float 932 32mm230 (220 with mute)0.106Middle (top with mute)3

impregnated paper

TRANSMISSION

2.56: 11.70: 11,21 : 11.00: 1

12.408.255.904,84

11.207,455.304.38

10,716,845.104.18

1111

1111

1111

(continued)

SPECIFICATIONS 183

750

BUSHINGS

4th gear bushing OD

4th gear bushing ID

4th gear bushing fitted ID

Layshaft bushing ID

Main shaft second gear bushing fitted

Layshaft third gear bushing fitted ID

Layshaft first gear bushing fitted ID

Selector spindle bushing, kickstartercase fitted ID

Camplate/quadrant bushing fitted ID

Kickstarter spindle bushing fitted ID

CAMPLATE PLUNGER SPRING

Free length

Spring rate

SELECTOR

Spindle diameter

Fork bore

DRIVE CHAIN

REAR CHAIN

CLUTCH

Type

Number of plates

Friction plate thickness

Push rod length

Pushrod diameter

Operating ball diameter

Clutch adjuster length

FUEL TANK

Fastback

LR Fastback

RoadsterFiberglassSteel

SS Hi-Rider

InterstateFiberglassSteel

OIL TANK

GEARBOX

FRONT FORKS

PRIMARY CHAINCASE


0.9060-0.9053 in. (23.012-22.995mm)

0.8145 0.8140 in. (20.688 20.675mm)

0.8133 0.8120 in. (20.657 20.625mm)

1.126-1.124 in. (28.60-28.549mm)

ID 0.8125-0.8115 in. (20.637-20.608mm)

0.8125 0.81 in. (20.637-20.57mm)

0.6885-0.6875 in. (17.488-17.462mm)

0.6290-0.6285 in. (15-976-15.964mm)

0.5005-0.4995 in. (12.713-12.687mm)

0.675-0.673 in. (17.145-17.094mm)

1.5 in. (38.1mm)

21 in.-lb.

0.3740-0.3735 in. (9.499-9.486mm)

0.3755-0.3745 in. (8.537-9.525mm)

92 pitches, 0.375 x 0.250 in., triple row

99 pitches, 0.400 x 0.380 in.

Multi-plate, oil bath, diaphragm spring

5 bronze, 4 steel0.125 in. (0.32mm)

9.813-9.803 in. (249.250-248.996mm)

0.237-0.232 in. (5.984-5.857mm)

1/2 in. (12.70mm)

0.904-0.894 in. (22.962-22.708mm)

CAPACITIES

3.9 gallons (15 liters)


2.7 gallons (10 liters)3.0 gallons (11 liters)


6.3 gallons (24 liters)6.6 gallons (25 liters)

6.0 pints (2.8 liters)


5 ounces (150cc) each leg

7 ounces (2(X)cc)

(continued)

184 APPENDIX

750 COMMANDO (continued)

DIMENSIONS

LengthWh?elbaseWidthGround clearanceFront brake diameterRear brake diameterBraking area, frontBraking area, rearExhaust system length

(flange to muffler tip)Front fork travelTurning circleSeat height

WEIGHT

Gross weight (oil and one gallon of fuel)RoadsterInterstate

Dry weightRoadsterInterstate

DistributionFrontRear

Gross vehicle rating

CHASSIS

87.5 in, (222cm)56.75 in (144cm)26 in, (66cm)

6 in. (15cm)7.95 in. (20.32cm)7 in. (17.78cm)

18.69 sq. in. (120 sq. cm)13.60 sq. in. (88 sq. cm)

60 in. (154.4cm)6 in. (15.2cm)

17 ft. 10 in. (518.16cm)33-34 in. (838-863mm) depending on mode!

422 1b. (191.44 kg)436 Ib. (197.75 kg)

395.4 1b. (179.3 kg)410 Ib. (186 kg)

45.5 percent54.5 percent859 Ib. (389.6 kg)

SPECIFICATIONS 185

850

GENERAL

Displacement

Bore

Stroke

Maximum torque

Compression ratio

CRANKSHAFT

Main bearing size

Big end journal diameter

Permissible end float

CONNECTING RODS

Big end ID (less bearing)

Rod side clearance

Rod end clearance

PISTONS

Diameter (bottom of skirt—standard)

Wrist pin boss ID

Wrist pin diameter

Rings (type)Top compressionSecond compression

CYLINDER BLOCK

Bore sizeGrade AGrade B

CYLINDER HEAD

Valve seat angle

CAMSHAFT

Bearing journal diameter

CAMSHAFT BUSHINGS

Fitted ID, left and right

PUSHRODS

Assembled length, inlet

Assembled length, exhaust

ROCKER SHAFT

Diameter

VALVE TAPPET CLEARANCES (Engine Cold)

Inlet

Exhaust

COMMANDO

ENGINE

50.5CU. in. (828CC)

3.030 in. (77mm)

3.503 in. (89mm)

56 ft.-ib. at 5,000 rpm

8.5: 1

1.18 X 2.84 X 0.75 in. (30 x 72 x 19mm)

1.7505-1.7500 in. (44.462 44.450mm)

0.005 0.015 in. (0.127-0.381mm)

1.895-1.8955 in. (48.133-48.145mm)

0.013-0.016 in. (0.33-0.406mm)

Less than 0.001 in. (0.0254mm)

3.028-3.071 in. (76.888-76.913mm)

0.6869-0.6867 in. (17.447-17.442mm)

0.6869-0.6867 in. (17.447-17.442mm)

Two compression, one oil control0.010-0.012 in. (0.254-0.305mm)0.008-0.012 in. (0.203-0.305mm)

3.0315-3.0320 in. (76.942-76.954mm)3.0320-3.0325 in. (76.954-76.967mm)

45°

0.8735 in. (22.187mm)

0.8750 in. (22.225mm)

8.166-8.130 in. (207.416-206.466mm)

7.321-7.285 in. (186.053-185.039mm)

0.4988-0.4985 in. (12.694-12.669mm)

0.006 in. (0.15mm)

0.008 in. (0.20mm)

(continued)

186 APPENDIX


VALVES

InletHead diameterStem diameter (plated area)

ExhaustHead diameterStem diameter (plated area)

VALVE GUIDES

Inside diameterOutside diameterWasher thickness

VALVE SPRINGS

Free lengthInnerOuter

Fitted lengthInlet innerInlet outerExhaust innerExhaust outer

INTERMEDIATE TIMING GEAR

Bushing diameter (finished)Shaft diameter

CAMSHAFT CHAINSizeNumber of linksIdeal adjustment

IGNITION TIMINGFully advanced position

CONTACT BREAKER

Point gapBolt thread size

SPARK PLUG

TypeGap

CARBURETORS

TypeMain jetNeedle jetNeedle positionThrottle valve

AIR FILTER

Type

1.490 in. (37.846mm)0.3115-0.3105 in. (7.912-7.886mm)

1.302 in. (33.0708mm)0.3115 0.3105 in. (7.912 7.886mm)

0.3145 0.3135 in. (7.988 7.962mm)0.6265-0.6260 in. (15.90-15.88mm)0.062 in. (1.574mm)

1.482 in. (37.642mm)1.618 in. (41.097mm)

1.197 in. (30.40mm)1.259 in. (31.98mm)1.222 in. (31.04mm)1.284 in. (32.61mm)

0.5627-0.5620 in. (14.292-14.274mm)0.5615-0.5610 in. (14.262-14.249mm)

0.375 in. x 0.225 in. (single-row, endless)38

3/16 in. (4.8mm) up and down on top run of chain

28^ BTDC

0.014-0.016 in. (0.35-0.4mm)Vi in. X 26 threads per inch

Champion N7Y or equivalent0.023-0.028 in. (0.59-0.72mm)

Two Amal concentric float 932 32mm260 (Mark II); 230 (Mark III)0.106Top

Impregnated paper (Mark II)Oil-wetted foam (Mark III)

(continued)

SPECIFICATIONS 187

850

RATIOS

Internal1st2nd3rd4th

Overall

With 19T gearbox sprocket(U.S. 1969-1972)

With 21T gearbox sprocket(U.S. 1973, U.K. 1972-1973)

With 22T gearbox sprocket(U.K. 1974-1975)

BUSHINGS4th gear bushing OD4th gear bushing ID4th gear bushing fitted IDLayshaft bushing ID

1st2nd3rd4th

1st2nd3rd4th

1st2nd3rd4th

Main shaft second gear bushing fittedLayshaft third gear bushing fittedLayshaft first gear bushing fitted

IDD

Selector spindle bushing, kickstartercase fitted ID

Camplate/quadrant bushing fitted IDKickstarter spindle bushing fitted

CAMPLATE PLUNGER SPRING

Free lengthSpring rate

SELECTORSpindle diameterFork bore

DRIVE CHAIN

REAR CHAIN

CLUTCH

TypeNumber of platesFriction plate thicknessPushrod lengthPushrod diameterOperating balance diameterClutch adjuster length

ID


TRANSMISSION

2.56: 11.70:11.21:11.00:1

12.40:18.25: 15.90: 14.84:1

11.20: 17.45 : 15.30: 14.38: 1

10.71 : 16.84: 15.10: 14.18:1

0.9060-0.9053 in. (23.012-22.995mm)0.8145-0.8140 in. (20.688 20.675mm)0.8133-0.8120 in. (20.657-20.625mm)1.126-1.124 in. (28.60-28.549mm)

ID 0.8125-0.8115 in. (20.637-20.608mm)0.8125-0.81 in. (20.637 20.57mm)0.6885-0.6875 in. (17.488-17.462mm)

0.6290-0.6285 in. (15.976-15.964mm)0.5005-0.4995 in. (12.713-12.687mm)0.675-0.673 in. (17.145-17.094mm)

1.5 in. (38.1mm)21 in.-lb.

0.3740 0.3735 in. (9.499-9.486mm)0.3755-0.3745 in. (8.537-9.525mm)

92 pitches, 0.375 x 0.250 in., triple row

99 pitches, 0.400 x 0.380 in.

Multi-plate, oil bath, diaphragm spring5 bronze, 4 steel0.125 in. (0.32mm)9.813 9.803 in. (249.250-248.996mm)0.237-0.232 in. (5.984-5.857mm)1/2 in. (12.70mm)0,904-0.894 in. (22.962-22.708mm)

(continued)

188 APPENDIX


FUEL TANK

Roadster

Steel

Hi-Rider

InterstateSteel

OIL TANK

GEARBOX

FRONT FORKS

PRIMARY CHAINCASE

DIMENSIONS

LengthWheelbaseWidthGround clearanceFront brake diameterRear brake diameterBraking area, frontBraking area, rearExhaust system length

(flange to muffler tip)Front fork travelTurning circleSeat height

WEIGHT

Gross weight (oil and one gallon of fuel)RoadsterInterstate

Dry weightRoadsterInterstate

DistributionFrontRear

Gross vehicle rating

CAPACITIES






5 ounces (150cc) each leg

7 ounces(200cc)

CHASSIS

87.5 in. (222cm)56.75 in. (144cm)26 in. (66cm)6 in. (15cm)7.95 in. (20.32cm)7 in. (17.78cm)18.69 sq. in. (120 sq. cm)13.60 sq. in. (88 sq. cm)

60 in. (154.4cm)6 in. (15.2cm)17 f t 10 in. (518.16cm)33-34 in. (838-863mm) depending on model

422 1b. (191.44 kg)436 Ib. (197.75 kg)

395.41b. (179.3 kg)410 Ib. (186 kg)

45.5 percent54.5 percent859 Ib. (389.6 kg)

INDEX

Air filter 21-22Alternator 122-123Automatic advance units 118-119

B

Backfiring 31Battery crossbar modification 124Battery electrolyte level 4-8Brake, front disc

Bleeding 142-143Caliper 143-144Inspection and assembly 142Master cylinder 140-141Pad replacement 143

Brake, front drumAdjustment 19-20Servicing 138-140

Brake, hydraulic disc 15-16Brake, rear

Adjustment 20Disc brake 156-157Drum brake 155-156Sprocket and brake assembly 155

Breaker point gap 116-118

cCables, control 18-19Carburetors

Adjustment 25-28Basic principles 109Cleaning and inspection 113Reassembly 114-115Removal and disassembly 110-112Servicing 109

Chain, primary 22Chain, rear 16-18Chaincase, primary 11

Charging system 122Clutch and primary drive

Assembly 64-70Clutch slip or drag 31Disassembly 55-62Inspection 62-64

Clutch cable 19Contact breaker 116-118Cylinder head

Assembly 44-45Bolts 22Disassembly 39-42Inspection 42-44Installation 46-48Removal 34-39

Cylinders and pistonsInspection 50-51Installation 52-53Removal 49-50

Electrical systemAlternator 122-123Automatic advance unit 118-119Battery 4-8Battery crossbar modification 124Capacitors 121Charging system 122Coils 121Contact breaker 116-118Ignition 116Ignition timing 119-121Lights and switches 127-128Magneto service 128-129Rectifier 123-124Spark plugs 24, 25, 122Starter (850 Mark III) 125-127Wiring diagrams 120-137Zener diode 124

EngineBreak-in 54-55

190 INDEX

Cylinder and pistons 49-53Cylinder head 34-48Lower end assembly and installation . . . . 82-89Lower end inspection 78-82Lower end removal and disassembly 70-78Noises, abnormal 31Oil changing 8-11Valve adjustment 48

Engine mounts, IsoclasticAdjustment, 750 and 850

Mark II, front mount 158-161Adjustment, 750 and 850

Mark II, rear mount 161-162Adjustment, 850 Mark III 162Assembly, front mount , 163-165Assembly, rear mount 165-166Inspection 158Installation 166Removal, front mount 162-163Removal, rear mount 163

F

Fork, front 13-15Frame 158Fuel system

Air filter 21-22Carburetors 109-115Fuel tank 115

Gearset and housingAssembly 105-108Inspection 104Removal 102-104

Gearshifting difficulties 33General information 1-3Grease fittings 20

H

Hub, front 144-147Hub, rear

Assembly, drum brakes 153-155Description 150Disassembly, disc brakes 153Disassembly, drum brakes 151-153Inspection 153

Idling, poor 31Ignition system

Automatic advance unit 118-119Capacitors 121Coil 121Contact breaker 116-118Description 116Dynamic (strobe) timing 121Static timing 119-120Tune-up 24-25

Isolastic system(see Engine mounts, Isolastic)

32127-128

Lighting problemsLights and switchesLubrication (see Maintenance and

Lubrication, periodic)

M

Magneto 128-129Maintenance and lubrication, periodic

Air filter 21-22Battery electrolyte level 4-8Brake adjustment 19-20Brake, hydraulic disc 15-16Chain, primary 22Chain, rear 16-18Control cables 18-19Engine oil 8-11Fork, front 13-15Grease fittings 20Primary chaincase 11Service intervals 4Swinging arm 12-13Tire pressure 4Transmission 11-12

Misfiring 31

Oil changingOverheating.

8-11.. 31

INDEX 191

Parts, ordering 1Pistons (see Cylinders and pistons)Piston seizure 31Power loss 31Primary chain adjustment 22Primary chaincase service 11Primary drive (see Clutch and primary drive)

Rear fork (see Swinging arm)Rectifier 123-124

sSafety hints 3Service hints 1-2Spark plugs 24-25,122Specifications, models

750 Commando 180-184850 Commando 185-188

Starter (850 Mark III) 125-127Starting difficulties 30Steering

Adjustment (1970 and earlier) 170-171Assembly 172Disassembly 171Inspection 171

Steering problems 32Supplies, expendable 3Suspension, front

Disassembly 167-170Inspection, reassembly, and installation 170Removal 166-167

Suspension, rear 172-173Swinging arm

Bushing replacement 175Inspection 174Installation 175-178Maintenance, periodic 12-13Removal 173-174

T

Throttle cable 26-28Tire pressures 4Tools 2-3Transmission

Description 90Gearset and housing assembly 105-108Gearset and housing inspection 104Gearset and housing removal 102-104Inner cover inspection 98-100Inner cover installation 100-102Inner cover removal 97-98Oil changing 11-12Outer cover inspection 93-95Outer cover installation 95-97Outer cover removal 90-93Performance improvement 181

TroubleshootingOperating difficulties 31-32Operating requirements 29-30Starting difficulties 30Troubleshooting guide 32-33

Tune-upCarburetor 25-28Cylinder head bolts 22Ignition system 24-25Intervals and sequence 22-23Valve clearance adjustment 23-24

Valve adjustment 23-24,48

wWheel, front 138Wheel, rear 148-150Wheel bearings 144-147, 150-155Wiring diagrams

650CC and 750cc Atlas and G15CS, 650CccManxman, S.S., and 12-Volt Twin MagnetoIgnition 130

750cc Commando (before 1971) 131750cc Commando (1971) 132-133850cc Commando Mark II

(1972-1974) 134-13585Occ Commando Mark III

(all years) 136-137

Zener diode 124

norton 750 commando

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