ebz7500/ 8500 workshop manual

Workshop Manual [2017]

EBZ7500/ 8500

This workshop manual describes the main maintenance items and procedures for the

Husqvarna Zenoah engine blower EBZ7500/ 8500. This manual is classified into three

categories.

Special tools for maintenance

Notice of teardown and reassembly

Inspection and adjustment of the carburetor

As reference information, the technical data, the maintenance standard and the

troubleshooting are listed, too.

After each item is thoroughly understood, apply the understanding to the actual maintenance

tasks. Frequently asked questions are also included in this manual. However, many cases

need rich maintenance experience and informed judgment. Please refer to this manual for

maintenance support.

“WARNING”

1. The contents of this manual are based on specifications as of 2017. The contents may be modified due to performance improvement or some other reason without notice.

2. Use Zenoah brand-name parts when replacing a part during maintenance, etc. The manufacturer does not bear any responsibility if trouble occurs owing to use of parts other than those endorsed by our brand.

3. Read this manual thoroughly before beginning the maintenance work, understand it, apply the content to the actual maintenance tasks and guide the customer if directions are needed.

Contents

-１-

1. Features of Engine Blower

1-1 Fan and Volute Case ······························· 2

1-2 Pipes ··················································· 3

1-3 Air Cleaner ············································ 4

1-4 Measures Against Static Electricity ············· 4

2. Strato-charged Engine

2-1 Outline ················································· 5

2-2 Operating Principle ································· 6

3. Constructions - Exploded View ············ 7

4. Technical Data

4-1 Blower ················································· 8

4-2 External Dimensions ······························· 9

4-3 Pipe and Nozzles ·································· 10

5. Special Tools

5-1 Description ··········································· 11

5-2 How to Use ·········································· 12

6. Notice of Teardown

6-1 Guard Net Removal ······························· 21

6-2 Lower Damper Removal ························· 21

6-3 Crankcase and Crankshaft Disassembly ····· 22

6-4 Oil Seal and Rearing Removal·················· 23

7. Notice of Reassembly

7-1 Engine Short Block Assembly ··················· 24

7-2 Handling of the bolt with a thread lock ········ 28

7-3 Muffler Installation ································· 29

7-4 Rotor Installation ··································· 29

7-5 Ignition Coil Installation ··························· 30

7-6 Coupling Installation ······························· 31

7-7 Carburetor Installation ···························· 31

7-8 Fan Installation ····································· 32

7-9 Recoil Starter Installation ························ 32

7-10 Engine Cover Installation ······················· 33

7-11 Intake Hose Installation ························· 33

7-12 Frame Installation ································ 34

7-13 Fuel Pipes Installation ··························· 35

7-14 Switch Cords and Cable Installation ········· 36

7-15 Elbow Installation ································· 36

7-16 Recoil Starter Assembly ························ 37

7-17 LHD-Throttle Lever Set Assembly ············ 40

7-17 RHD-Throttle Lever Set Assembly ··········· 42

8. Carburetor

8-1 Technical Data······································ 44

8-2 Description ·········································· 45

8-3 Inspection ··········································· 46

8-4 Adjustment ·········································· 50

9. Maintenance Standards/ Tightening Torques

9-1 Standards and Service Ability Limit ··········· 53

9-2 Tightening Torque ································· 54

10. Troubleshooting

10-1 Engine does not star ···························· 55

10-2 Engine stop during operation ················· 56

10-3 Engine cannot be stopped ····················· 56

10-4 Lack of output power or unstable

revolution ·········································· 57

10-5 The amount of the wind is weak ·············· 57

10-6 Others ·············································· 58

-２-

1 . Features of Engine Blower

1-1 Fan and Volute Case

Air is sucked from the whole circumference of the full cover type guard net and from the side structure of the

newly designed blow molding frame to send a lot of air to the fan. The fan uses a half-closed fan, optimizing

the air flow with the new flat volute case, realizing the very best of the air volume and wind velocity.

Intake from the side of the frame.

Guard Net

New type Flat Volute Case

Half-closed Fan

The notches are formed in the shroud (wing covering) and

height of fins is increased while maintaining rigidity in

order to increase wind volume and decrease the weight.

Blow molded

new frame

-３-


1-2 Pipes

BZ7500

The tip of the pipe end is cut obliquely so that the

wind flows slightly downward. By letting the wind flow

downward, holding of the pipe feels lightly. It

promotes easy operation.

EBZ8500

By increasing the diameter of the aperture of the

pipe end, the wind loss at the pipe outlet is reduced.

The maximum air volume in this class is acquired.

EBZ7500/ 8500

The new spiral type flexible hose has no sharp on its

surface contrary to the conventional flexible hose. It

is hard to split and has excellent durability.

In addition, wind resistance is reduced compared

with conventional uneven path.

Wind direction 3 to 5 degrees downward

Indication of the orientation of installation

NOTE:

If the pipe end is set upside down, it gives you a powerful feeling to blow the object far, but you will need power to hold the grip.

Cut it obliquely.

Outlet inner diameter φ84mm

φ76mm Flare

Conventional flexible hose

New type spiral flexible hose

-４-


1-3 Air Cleaner

EBZ7500/ 8500

It is equipped with a large capacity cleaner with

double structure of pre-filter and paper filter. The

high cleaning efficiency realizes longer time to

clogging even at sites where there are many dust.

EBZ8500

The fresh air intake system is used. Because the

clean air in the volute case is taken in directly through

the dedicated passage, it is powerful and the

maintenance interval can be lengthened.

1-4 Measures Against Static Electricity

A conductive throttle lever discharges static

electricity through the hands of the operator.

Throttle Lever

Air Cleaner Cover

Paper Filter

Pre-filter

Air Cleaner Body

Fresh Air Intake Passage

Air Cleaner Case

Volute Case

-５-


2-1 Outline

■ Efforts to the exhaust gas regulations

Husqvarna Zenoah has developed its own "Strato-charged

Engine" as a two-stroke engine compliant with exhaust gas

regulations since 1999, and it has been in compliance with the

regulations of each country starting from the US.

The Strato-charged engine realizes clean exhaust while taking

advantage of two-stroke engine.

■ Structure

Normally, approximately 30% of unburned gas is discharged in a two-stroke engine, because air-fuel

mixture pushes out the combustion gas. However, Husqvarna Zenoah's Strato-charged engine adopts

"air-guided stratified scavenging system" which introduces leading air to the scavenging port separately

from the air-fuel mixture. The leading air pushes out the combustion gas in order to prevent blowing out

of unburned gas resulting in reduction of the concentration of hydrocarbons in the exhaust gas.

■ Features

Because it does not use any special equipment, it is lightweight with a simple structure.

Excellent cooling performance promotes stable output performance even in continuous operation in

summer.

It realizes low fuel consumption of 40% or less. (In comparison with our previous model)

混合気

Lead Air Venturi

Air-fuel Mixture Venturi

Carburetor

Scavenging Port

Piston Groove

Lead Air Intake Port

Air-fuel Mixture

Intake Port

-６-


2-2 Operating Principle

1. As the piston proceeds through the upstroke

of the intake cycle, the crankcase vacuum

sucks the lead air in through the scavenging

port via the groove on the piston skirt.

2. As the piston begins its downstroke after top

dead center, a scavenging port starts to open

and lead air in the scavenging port moves into

the cylinder earlier than the air-fuel mixture.

3. As the piston begins its upstroke after bottom

dead center, burnt gas in the cylinder is pushed

out through the exhaust port by lead air.

Therefore, almost no air-fuel mixture is emitted.

Piston

Exhaust Port

Burnt Gas

Air-fuel Mixture

Lead Air

Air-fuel Mixture

Lead Air

-７-

3. Constructions - Exploded View

7-9 Recoil Starter Installation (see page 32)

7-16 Recoil Starter Assembly (see page 37)

7-10 Engine Cover Installation (see page 33)

7-5 Ignition Coil Installation (see page 30)

7-4 Rotor Installation (see page 29)

7-14 Switch Cords and Cable Installation

(see page 36)

7-3 Muffler Installation (see page 29)

7-13 Fuel Pipe Installation

(see page 35)

6-1 Guard Net Removal (see page 21)

7-12 Frame Installation (see page 34)

7-17 LHD-Throttle Lever Set

Assembly (see page 40)

7-8 Fan Installation (see page 32)

7-15 Elbow Installation (see page 36)

7-11 Intake Hose Installation

(see page 33)

6-2 Lower Damper Removal

(see page 21)

7-6 Coupling Installation

(see page 31)

7-7 Carburetor Installation (see page 31)

8 Carburetor (see page 44)

6-3 Crankcase and Crankshaft Disassembly (see page 22)

6-5 Oil seal and Bearing Removal (see page 23)

7-1 Engine Short Block Assembly (see page 24)

7-17 RHD-Throttle Lever Set

Assembly (see page 42)

-８-

4. Technical Data

4-1 Blowers

Item Unit Specifications

Remarks Category － Back-pack Engine Blower

Engine Types － GZ66N5 GZ76N3

Blower Models － EBZ7500 EBZ8500

Cycle － Two-stroke ←

Number of Cylinders － 1 ←

Valve Type － Piston valve ←

Cylinder Bore mm 47.5 51

Stroke mm 37 ←

Displacement cm3 65.6 75.6

Fuel － Lubricating blended gasoline ←

Engine lubrication － Fuel-oil mixture ←

Engine lubrication Oil － Two-stroke engine oil ←

Mixing Ratio － Zenoah FC 40:1/ Zenoah FD 50:1 ←

Carburetor Type － Diaphragm type rotary throttle valve ←

Models － Walbro WYA-236A Walbro WYA-237A

Starting Method － Recoil starter ←

Ignition System － Digital controlled (CDI) with automatic timing advance

← Digital control misfire for excessive speed maximum speed: 8,500 rpm

Ignition Timing BTDC °/rpm 30.5/ 7,000 ←

Spark Plug Type － NGK CMR7H ← Noise-proof

Gap mm 0.6 to 0.7 ←

Stopping Method

Type － Primary coil short-circuiting ←

Switch － Push type ←

Cooling System － Forced air cooling ←

Air Cleaner Element Type － Primary: Dry puff

Secondary: Dry paper ← Two stage filters

Output Axle Rotation Direction

－ Counterclockwise ← View from output axle

Dimensions

Length mm 354※ 357※ ※Throttle arm vertical state

Width mm 536※ 535※ ※Throttle arm vertical state

Height mm 499 540

Body dry weight with standard pipes

kg 10.6 (9.6) 11.2 (10.2) ( ): Elbow included,

without blower pipes

Fuel Tank Capacity L 2.1 2.3

Idling Speed rpm 2,000 ← Idling speed stability：±200

Operating Speed rpm 7,250 ← Wide open throttle stability：±100

Pipe Nozzle Diameter mm 72 84

Average air volume at aimed blowing point

m３/ m 21.8 25.7 ANSI

Maximum air speed at aimed blowing point

m/s 105.6 92.2 ANSI

Maximum Output kW/rpm (PS/rpm)

2.8/ 7,200 (3.8/ 7,200)

3.3/ 7,250 (4.49/ 7,250)

Fuel Consumption L/h 1.85 2.07 Under actual blower state

Ambient noise at 15 m from the blower

dB(A) 77 ← ANSI B.175.2-2000

Noise at operator dB(A) 103.4 103.2 Reference

Sound Power Level dB(A) 110 ← ISO11094 (EBZ7500/ 8500)

-９-

4. Technical Data

4-2 External Dimensions

Unit：mm

Models A B BB C D

EBZ7500 354 536 479 499 1198

EBZ8500 357 535 497 540 1198

Illustration shown is EBZ7500.

☆: Reference.

-１０-

4. Technical Data

4-3 Pipes

Unit：mm

Part No. 576 56 47-01 576 56 51-01 576 56 48-01

Name Flexible Hose Grip Assembly Swivel Joint

Appearance

Applicable Inner diam.

d1

Inner diam.

d2

Length

L1 Inner diam. d3

Outer diam.

D4

Outer diam.

D5

Length

L2

EBZ7500 φ99.5 φ99.5 349 φ97.4 φ99 φ103 340

EBZ8500

Part No. 576 56 49-01 576 56 50-01 576 57 64-01

Name Straight Pipe Pipe End Pipe End

Appearance

Air velocity type

Air volume type

Applicable Inner diam.

d6

Outer diam.

D7

Length

L3

Inner diam.

d8

Inner diam.

d9

Length

L4

Inner diam.

d10

Inner diam.

d11

Length

L5

EBZ7500 φ103 φ103 380

φ103 φ72 350 ― ― ―

EBZ8500 ― ― ― φ103 φ84 350

-１１-

5. Special Tools

5-1 Description

Tool Name Tool Number Appearance Usage

Torx Wrench 2850-96410

Size: T20/ T25/ T27 Bolt and screw loosen/ tighten

Socket Key H502502301

Size: M10

Damper nut loosen/ tighten

Puller Assy. 577 40 97-01

Rotor and coupling removal (see pages 13

and 14)

Gauge

0.3mm

516 88 03-01

(2750-96240)

Ignition coil setting (Air gap) (see page 15)

Rod Assy. 516 18 29-01

(1101-96220)

Piston pin removal or installation

(see page 16)

Bearing Guide 577 40 98-01

Main bearing installation (see page 16)

Crankshaft

Installing Tool

① 582 04 35-01

② 582 04 36-01

③ 01582-01613

Press the crankshaft to the PTO side

crankcase.

Guide also used for press of the oil seals.

(see pages 16, 17 and 18)

①

② ① Guide ② Bolt ③ Nut

Crankcase

Support 577 41 01-01

When pressing the bearing, oil seal and crankshaft, support the crankcase (see pages 16 and 17).

① ②

③

-１２-

5. Special Tools

5-1 Description

Tool Name Tool Number Appearance Usage

Pressure

Vacuum Gauge H531030623

Engine seal check (see page 19)

Pressure Tester

Attachment H503844001

Set in the hole of the spark plug, and

connect the pressure gauge

(see page 19).

Outlet Cover

Plate H502541102

Closure of exhaust port and inlet port

(see page 19)

Compression

Gauge (φ14mm)

Adapter Size:

(φ10mm)

H531031686

583 84 98-01

Compression pressure check (see page 18)

Piston Fitting Kit H502507001

Piston installation (see pages 17 and 20)

Fuel Filter Hook H502508301

Suspending the fuel filter

Fuel Filter

φ10 Adapter φ10

Stopper

Do not use.

φ10

-１３-

5. Special Tools

5-2 How to use

Item Procedures

-1)

Rotor Removal

1. Remove the recoil starter, the engine

cover, the intake hose and the spark plug.

2. Turn the rotor to the clockwise (CW) 90

degrees from the TDC.

NOTE:

The piston TDC is the position where

the "S" mark of the rotor is aligned with

the center of the cylinder.

3. Insert the recoil rope into the cylinder from

the plug hole to stop the movement of the

piston.

4. Remove the mounting nut of the rotor.

NOTE:

Turn the rotor counterclockwise (CCW)

slowly, contact the piston head to the

recoil rope lightly and loosen the nut.

5. Set the puller (special tool) to the rotor.

NOTE:

When attaching the puller bolts, screw

in more than half of the threaded

portion to the rotor.

6. Tighten the center bolt of the puller and

remove the rotor from the crankshaft.

Recoil Rope

“S” Mark

Rotor

Puller Bolts

17 mm Hex

Puller

Rotor

Mounting Nut

(14 mm Hex)

-１４-

5. Special Tools

5-2 How to use

Item Procedures

-2)

Coupling Removal

1. Remove the recoil starter, the engine

cover, the intake hose, the fan, the volute

case and the spark plug.

2. Turn the rotor to the counterclockwise

(CCW) 90 degrees from the TDC. Insert

the recoil rope into the cylinder from the

plug hole to stop the movement of the

piston.

3. Remove themounting nut of the coupling.

NOTE:

Turn the coupling counterclockwise

(CCW) slowly, contact the piston head

to the recoil rope lightly and loosen the

nut.

4. Set the puller (special tool) to the coupling.

NOTE:

When attaching the puller bolts, screw

in more than half of the threaded

portion to the coupling.

5. Tighten the center bolt of the puller and

remove the coupling from the crankshaft.

Recoil Rope

Rotor

Coupling

“S” Mark

Mounting Nut

(14 mm Hex)

17 mm Hex

Coupling

Puller Bolts Puller

-１５-

5. Special Tools

5-2 How to use

Item Procedures

-3)

Ignition Coil Installation (Adjusting air gap)

1. Apply thread lock to the mounting bolts.

Set the spacers, the ignition coil and the

terminal, and temporarily tighten the

mounting bolts。

Thread Lock: Three Bond #1342/1342H

or equivalent

2. Insert the gauge (special tool) between the

rotor magnet metal and ignition coil.

Tighten the mounting bolts while pushing

the ignition coil against the rotor.

Torque: 2.45～3.92N･m (25～40kgf･cm)

NOTE:

When contacting the iron core of the

ignition coil and part of the rotor

magnet metal, the engine may stop

suddenly. Secure the air gap (03.mm)

using the gauge.

[Resistance]

The resistance values shown above are the reference values for resistance tester

measurement. The resistance value within the normal range shows no internal leakage or

any other defect.

Ignition Checker (Tool No. 3699-90247)

We supply the measurement

equipment (Ignition Checker) that can

measure spark energy while the

engine is running. When measuring

the spark energy, discharge gaps are

different depending on the connected

place of the alligator clip.

Refer to the ignition checker

manufacturer’s instruction details.

Rotor

Gauge (0.3mm)

Ignition Coil Spacer

0.3mm

0.3mm

プラグキャップ

Mounting Bolts M4x 22L (T27)

Spacer

High-tension Cord

Iron Core

Primary

Lead

Resistance (Reference)

Air Gap Primary side

(Iron Core ↔ Primary Terminal) Secondary Side

(Iron Core ↔ Secondary Side)

90kΩ±20％ 2kΩ±10％ 0.3mm

Discharge Window

If connected to the engine.

Discharge gaps: 6mm

If connected to the spark plug.

Discharge gaps: 4mm

Discharge Gap Adjustment Knob Plug Cap

-１６-

5. Special Tools

5-2 How to use

Item Procedures

-4)

Piston Pin Removal/ Installation

1. Remove the cylinder from the engine short

block.

2. Remove the snap ring on the fan side of

the piston and remove the piston pin from

the piston.

NOTE:

The piston pin can be removed without

using a tool usually. If it is difficult to

remove, use the rod assy. (special tool)

to push out from the piston.

-5）

Press of Bearing Illustration shows the MAG side. PTO side similar.

-S: Starter side

1. Set the support (special tool) outside of

the crankcase-S as shown.

2. Tap the bearing with a plastic hammer

lightly and fit it into the crankcase

horizontally.

3. Insert the bearing guide (special tool) to

the bearing and press the bearing into the

crankcase using a press.

-6）

Press of Starter side Oil Seal

1. Set the support (special tool) inside of the

crankcase-S as shown.

2. Press the guide (special tool) against the

oil seal and press the oil seal into the

crankcase-S with a press.

Guide

(① of Crankshaft

installing tool)

Oil Seal

Bearing

Support

Rod Assy. Piston

Piston Pin

Snap Ring

Bearing Guide

Crankcase-S

Crankcase-S

Support

-１７-

5. Special Tools

5-2 How to use

Item Procedures

-7)

Press of Crankshaft -F: Fan side -S: Starter side

In the case of the crankshaft reuse, the fit

between the crankshaft and the crankcase-F

side of the bearing may be slightly tight.

1. Insert the crankshaft until halfway into the

crankcase-F.

2. Insert the guide of the crankshaft installing

tool (special tool) into the crankshaft, and

contact the tip of it to the inner race of the

bearing. Screw the bolt to the crankshaft

and fix it with the nut as shown.

3. Fix the connecting rod with the plate of

piston fitting kit (special tool) so that the

crankshaft does not turn.

4. Fix the bolt and insert the crankshaft into

the bearing while screwing the nut.

NOTE:

After press, rotate the crankshaft to

check the operation of the bearing.

If the movement of the bearing is

heavy, tap the bolt head with a plastic

hammer to release the pressure on the

bearing.

5. Set the support (special tool) outside of

the crankcase-S as shown.

6. Set the crankcase gasket and temporarily

install the mounting bolts.

7. Set the guide of the crankshaft installing

tool (special tool) on the crankcase-F and

press the crankshaft into the crankcase-S

with a press.

NOTE:

When inserting the crankshaft, do not

damage the lip of the oil seal on the

crankcase-S side at the edge of the

shaft.

Crankshaft Plate

Guide

Nut

Tighten. Bolt Fix. Crankcase-F

Guide Bolt Crankshaft

Bearing

Nut

Crankcase-F

Crankcase Gasket

Support

Crankcase-S

Crankcase-F

Press Guide

(① of Crankshaft

installing tool)

-１８-

5. Special Tools

5-2 How to use

Item Procedures

-8）

Press of Fan side Oil Seal

1. Insert the oil seal to the crankcase-F until

it stops with your fingers.

NOTE:

When inserting the oil seal, do not

damage the lip of it at the edge of the

crankshaft.

Insert the oil seal horizontally so as

not to be tilt.

Because there is a groove preventing

coming off on the outside of the oil

seal, its insertion is not easy.

2. Place the guide (special tool) against the

oil seal and tap it with a hammer to press

the oil seal into the crankcase-F.

NOTE:

After press, rotate the crankshaft to

check the operation of the bearing.

-9)

Compression Pressure Check

1. Warm-up the engine for at least 5 minutes.

NOTE:

After warm-up, the engine and the

muffler will become hot. Be careful

not to burn yourself.

2. Remove the attachment of the

compression gauge (special tool) and

attach the adapter (φ10mm).

3. Remove the spark plug and set the

compression gauge (special tool) to the

cylinder.

4. Pull the recoil knob quickly and strongly

about 5 times.

More than 8.4 kg/cm2 (872kPa) is fine.

“This value is only an estimate.”

NOTE:

Engine parts is not thermal expansion

in the warm-up the shortage, or

immediately after replacement with

the new part, cannot be to correctly

measure the compression pressure.

Compression Gauge (φ14mm)

Adapter (φ10mm)

Oil Seal Push with a finger.

Crankcase-F

Attachment Do not use.

Guide

(① of Crankshaft

installing tool)

-１９-

5. Special Tools

5-2 How to use

Item Procedures

-10)

Engine Seal Check

1. Remove the muffler and the gasket.

2. Temporarily install the muffler and insert

the outlet cover plate (special tool)

diagonally between the muffler and the

exhaust port of the cylinder. Tighten the

bolts, then close the exhaust port.

3. Remove the spark plug, set the pressure

tester attachment (special tool) to the

cylinder.

4. Remove the intake cup, the carburetor

and the gasket.

5. Temporarily install the carburetor and the

intake cup, and insert the outlet cover

plate (special tool) between the carburetor

and the insulator. Tighten the bolts, then

close the intake port.

NOTE:

Cut the outlet cover plate so that the

intake port is closed surely.

Outlet Cover Plate

Carburetor

Gasket

Intake Cup

Muffler

Pressure Tester Attachment

Gasket

Outlet Cover Plate

Muffler

Outlet Cover

Plate

Outlet Cover Plate

Cut the shaded area.

Cut the shaded area.

-２０-

5. Special Tools

5-2 How to use

Item Procedures

-10)

Engine Seal Check

6. Connect the pressure vacuum gauge

(special tool) to the pressure tester

attachment of the cylinder.

7. Adjust the "Pressure Mode" press to

80 kPa.

After 30 seconds, if the seal stays at

60 kPa, the sealing should be fine

NOTE:

After installing the muffler, operate the

engine by wide open throttle more than

one minute, and retightening the

mounting bolts.

-11)

Piston Installation

When inserting the piston into the cylinder, fix

the piston with the plate of the piston fitting kit

(special tool) and hold the piston rings with

the ring tool.

Ring Tool Piston

Cylinder

Piston Rings

Plate

切

替

え

ノ

ブ

Pressure Vacuum Gauge

Select Knob

Select Knob

Pressure Mode

Vacuum Mode

-２１-


6-1 Guard Net Removal

The guard net is mounted by four clips. The removal

procedure is shown below.

1. Loosen the resin screw of the clip and remove it

completely.

NOTE:

When loosening the resin screw, securely fit

the Phillips screwdriver into the (+) of the

screw head. If not fitted, the screw head will

be damaged.

2. Insert the flat tip screwdriver between the guard

net and the frame, twist the screwdriver to pull out

the clip, and remove the guard net from the

frame.

NOTE:

Do not damage the guard net and frame with

the screwdriver.

6-2 Lower Damper Removal

Remove the volute case from the frame.

Remove the cover and pull out the lower damper

from the groove of the volute case.

Clip

Flat Tip Screwdriver

Resin Screw

Guard Net

Volute Case

Screws (3)

Cover Lower Damper

Frame

Mounted positions (4)

-２２-


6-3 Crankcase and Crankshaft Disassembly

1. Remove the mounting bolts, twist the flat-tip

screwdriver at the two notches of the crankcase,

then separate the crankcase-S and the

crankcase-F. If necessary, gently tap with a

plastic hammer to the crankcase-F.

2. Remove the crankcase-F from the crankcase-S

with the crankshaft.

NOTE:

The crankshaft cannot be removed from the

crankcase-F in this state because the main

bearing of the crankcase-F and the crankshaft

are very tight fitting.

Crankcase-S

Crankshaft Crankcase-F

Crankcase-S

Notch

Notch

Opposite side

Crankcase-F

Crankcase-F

Crankcase-S

-２３-


6-3 Crankcase and Crankshaft Disassembly

3. Use the press to remove the crankshaft from the

crankcase-F.

NOTE:

Do not remove the crankshaft by tapping with

an iron hammer because it may cause the

rotation of the crankshaft will be off-balance

or the thread may be damaged.

6-4 Oil Seal and Bearing Removal

Check wear of the oil seal, rattling and seizure of

the bearing. If necessary replace them.

If the bearing press-fitting portion of the crankcase

is worn, replace the crankcase at the same time.

NOTE:

Be sure to remove the bearing using a press.

If do not use a press, the crankcase may be

damaged.

Never reuse the bearings and the oil seals.

Press

Guide

(Commercially available tool)

Crankcase

Bearing

Support

Press

Crankshaft

Crankcase-F

Support

Bearing

Oil Seal

Crankcase-F

Crankcase-S

Bearing

Oil Seal

-２４-


7-1 Engine Short Block Assembly

1) Lubricating and Degreasing

Apply two-stroke engine oil to the inner surface of the main bearings, needle bearing, between the crank

weight and the connecting rod large end.

Apply two-stroke engine oil to the inner surface of the cylinder and the outer periphery of the piston

excluding the piston head.

Apply heat-resistant grease No.2 to the inner surface and lip of the oil seals.

Degrease the outer surface of the main bearings and the bearing contact surface of the crankcase.

Degrease the taper and thread portion of the crankshaft.

Degrease the outer surfaces of the oil seals.

Crankcase-F

Crankcase-S

Oil Seal

Starter side

Oil Seal

Crankcase

Oil Seal

Two-stroke oil applying location

Degreasing location

Cylinder

Bolts (4) M5x 22L (T27)

Torque: 5.88～8.82N・m (60～90kgf・cm)

Snap Ring Piston

Needle Bearing

Piston Pin Fan side

Bearing

Degreasing

Bearing

Connecting rod

large end

Bolts (4) M5x 30L (T27)

Torque: 5.88～7.84N・m (60～80kgf・cm)

Degreasing

Degreasing

-２５-



2) Main Bearing and Oil Seal

Press the bearing using the bearing guide of

the special tool (see page 16).

Press the oil seal using the guide of the

crankshaft installing tool (special tool) (see

page 16).

NOTE:

After assembling the crankshaft, press the oil

seal of the crankcase-F (See page 18）.

NOTE:

Never reuse the bearings and the oil seals.

3) Crankshaft

Confirm the assembly direction of the

crankshaft. Set the crankshaft to the TDC

position, the keyway of the shaft is downward

and the short taper is the crankcase-F side.

Insert the crankshaft into the crankcase-F

using the crankshaft installing tool of special

tool (see page 17).

Check that the crank weight edge and the

clearance of both sides of the crankcase edge

be equal. When a gap is not equal, tap the

crankshaft of the side where a gap is small

with a plastic hammer and do a gap equally.

Bearing Guide

Bearing

Guide

1.5mm

Guide

Crankshaft

Oil Seal

Plate

Crankshaft Installing Tool

Crankshaft

Crankcase-F

Crank Weight

Crankcase-S Crankcase-F

Confirm that a gap is equal.

Crankcase-F side

TDC position

Crankcase-F

Keyway

Short taper

Crank Weight

Oil Seal

-２６-



4) Crankcase Gasket

NOTE:

Be sure to use the new parts of the crankcase

gasket.

Cut off the crankcase gasket ends exceeding

the cylinder mating surface.

When cutting the gasket, cut it outward from

inside, so that the gasket will not fall into the

inside of the crankcase.

5) Piston Ring

Align the end gap of the piston ring exactly with

stopper pin of the piston.

6) Piston, Piston Pin and Snap Ring

Make sure to point the triangle mark on the

piston head to the exhaust (muffler) side.

Install the piston pin with the rod assy. of

special tool (see page 16).

Fit the snap ring in the groove of the piston

firmly and turn the end gap of the snap ring to

the opposite side of the notch.

After the assembly, check that it moves

smoothly in the groove by turning the snap

ring with a thin tool of the tip. If the snap ring is

not securely fitted into the groove, it does not

move smoothly.

NOTE:

If the snap ring does not fit properly into the

groove or the end gap of the snap ring is

incorrectly positioned, and the snap ring

come off during operation, it may damage the

engine.

Never reuse the snap ring, replace it with a

new on.

Stopper Pin

Piston Ring

Snap Ring

Piston Pin

Groove

End Gap

Notch

Stopper Pin

Piston

Crankcase

Triangle Mark

Exhaust side

Crankcase Gasket Cut off.

-２７-



7) Cylinder Gasket

When setting the cylinder gasket, make the

arrow mark to the fan side.

8) Scavenging Port Cover

Do not remove the scavenging port cover as

much as possible. If removed the scavenging

port cover, make sure to apply the liquid gasket

to the mating surface with the cylinder and install

the scavenging port cover.

NOTE:

The liquid gasket should be applied

continuously without any gaps to ensure

high sealing accuracy of the mating face of

the scavenging port cover and the cylinder.

Liquid gasket:

Three Bond #1217F or equivalent

Torque: 2.0～3.5N･m (20～35kgf･cm)

Cylinder Gasket

Arrow Mark

Scavenging Port Cover

Illustration is the fan side;

starter side is similar.

-２８-


7-2 Handling of the bolt with a thread lock

As for EBZ7500/ 8500, a thread lock is applied to the ignition coil, the recoil starter, the insulator mounting

bolts, and the upper damper mounting screws. When handling the mounting bolts or screws, pay attention to

the following items.

NOTE:

When Loctite242 is applied exceeding the proper quantity, the crankcase's internal thread may be

broken. If too much Loctite242 is applied and the crankcase is damaged due to this, Husqvarna

Zenoah will not warrant the damaged case.

【Reuse the bolt/ screw】

1. Remove the old thread lock on the bolt or screw

by using the dies.

2. Remove the old thread lock on the thread holes

of the crankcase, cylinder and the upper damper

by using the tap.

3. Degrease the thread portions, and apply a new

thread lock to the mounting bolt or screw.

NOTE: When tightening the bolt with the old thread lock having stuck, damage the thread portions of the engine side.

Thread Lock:

Three Bond #1342

LOCTITE #222, LOCTITE #242 or equivalent

【Replace the bolt/ screw】

When replacing the new mounting bolts or screw,

remove the old thread lock on the thread holes of

the crankcase, cylinder and the upper damper by

using the tap.

Ignition Coil

Mounting Bolt (2)

M4×0.7 L22

Low intensity:

Loctite #222 or only

one drop of Loctite

#242

Recoil Starter

Mounting Bolt (4)

M5×0.8 L16

Insulator

Mounting Bolt (4)

M5×0.8 L27

Middle intensity:

Loctite #242

Upper Damper

Mounting Screw (2)

M5×0.8 L16

Dies

Thread

Tap

About 10mm

Apply a thread lock to the

coil mounting bolt in the

range of about 3mm from

the tip of the thread.

About 3mm

Middle intensity:

Loctite #242

Middle intensity:

Loctite #242

Thread Hole

Tap

Thread Hole

-２９-


7-3 Muffler Installation

Check the muffler for deformation and cracks. If

necessary, replace it with a new one.

Remove the carbon deposits that have

accumulated in the muffler with a screwdriver.

NOTE:

Do not burn the carbon deposits in the muffler

by overheating with the gas torch. If

overheated, it may cause deformation of the

muffler, melting of the inner glass wool, etc.

Remove the carbon deposits on the engine side

exhaust port with the wood stick.

NOTE:

Block the exhaust port with the piston so that

carbon deposits does not fall in the cylinder

Evenly tighten the muffler mounting bolts.

Torque: 7.87～11.76N･m (80～120kgf･cm)

Remove the diffuser and remove the carbon

deposits that have accumulated on the spark

arrester with a wire brush. If necessary, replace it

with a new one.


7-4 Rotor Installation

1. Parallel the flat surface of the key to the center

line of the crankshaft, and set it in the keyway of

the crankshaft. Align the keyway of the rotor with

the key to crankshaft surely and insert it.

NOTE:

Make sure that there is no adhesion of oil or

dust on the tapered surface and the threaded

portion of the crankshaft and rotor.

2. Turn the rotor to the clockwise (CCW) 90

degrees from the TDC. Insert the recoil rope into

the cylinder from the plug hole to stop the

movement of the piston (see page 14)

3. Tighten the mounting nut and fix the rotor.

Torque: 24.5～34.3N･m (250～350kgf･cm)

Spark Arrester

Muffler

Gasket

Diffuser

Rotor

Crankshaft

Key

Parallel.

Rotor

Mounting Nut

Exhaust Port

Bolts (2)

M6x 30L (T27)

Bolt (1)

M6x 16L (T27)

Bolts (4)

M4x 8L (T27)

Spark Arrester

-３０-


7-5 Ignition Coil Installation

1. Apply thread lock to the mounting bolts.

Set the spacers, the ignition coil and the

terminal, and temporarily tighten the mounting

bolts.

Thread Lock: Three Bond #1342/ 1342H or

LOCTITE #242 or equivalent

2. Insert the gauge (special tool) between the rotor

magnet metal and ignition coil. Tighten the

mounting bolts while pushing the ignition coil

against the rotor (see page15).


NOTE:

Tighten the mounting bolt (A) so that the

terminal does not contact the ignition coil

and the crankcase.

3. Fix the grommet of high tension cord/ switch cord

to the notch of the crankcase.

Rotor Gauge (0.3mm)

Terminal

Do not contact.

Ignition Coil

Spacers

Terminal

Bolts (2) M4x 22L (T27)

Bolt (A)

Grommet

-３１-


7-6 Coupling Installation

1. Turn the rotor to the clockwise (CW) 90 degrees

from the TDC. Insert the recoil rope into the

cylinder from the plug hole to stop the movement

of the piston (see page 13).

2. Parallel the flat surface of the key to the center

line of the crankshaft, and set it in the keyway of

the crankshaft. Align the keyway of the coupling

with the key to crankshaft surely and insert it.

NOTE:

Make sure that there is no adhesion of oil or

dust on the tapered surface and the threaded

portion of the crankshaft and coupling.

3. Tighten the mounting nut and fix the coupling.

Torque: 24.5～34.3N･m (250～350kgf･cm)

7-7 Carburetor Installation

1. Align the holes of the insulator gasket and the insulator to the cylinder. Tighten the mounting bolts.

Torque: 3.92～5.88N･m (40～60kgf･cm)

2. Align the holes of the carburetor gasket, the carburetor and the intake cup to the insulator. Tighten the

mounting bolts.

Torque: 2.94～4.41N･m (30～45kgf･cm)

Parallel.

。

Coupling

Key

Coupling

Mounting Nut

Key

Carburetor

Carburetor Gasket

Intake Cup

Insulator Gasket

Insulator

Bolts (2) M5x 60L (T27)

Bolts (4) M5x 27L (T27)

-３２-


7-8 Fan Installation

1. Install the engine short block to the volute vase.

Torque: 5.88～7.84N･m (60～80kgf･cm)

2. Align the holes of the coupling and the fan.

Tighten the mounting bolts and attach the fan to

the coupling.

Torque: 9.8～13.7N･m (100～140kgf･cm)

NOTE:

Tighten the four mounting bolts with equal

torque in diagonal order.

7-9 Recoil Starter Installation

Fit the recoil starter to the crankcase, and fix it

with the mounting bolts.

Torque: 2.94～4.41N･m (30～45kgf･cm)

When fitting the recoil starter to the crankcase,

engage the ratchet of the rotor and cam plate

hook of the recoil starter while pulling little starter

knob.

Fan

Recoil Starter

Crankcase-S

Bolts (4) M5x 16L (T27)

Bolts (4)

M6x 26L (T27)

Bolts (4) M6x 50L (T27)

Volute Case

Engine Short Block

-３３-


7-10 Engine Cover Installation

Fit the engine cover to the volute case, and fix it with

the mounting screws.

Torque: 2.94～3.92N･m (30～40kgf･cm)

NOTE:

If the mounting screws are tightened tightly,

threads of the volute case may be damaged.

NOTE:

When installing the engine cover, insert the

lower edge of the muffler gasket inside the

engine cover to protect the fuel tank from

exhaust heat.

7-11 Intake Hose Installation

Before installing the intake hose, apply grease to

the air cleaner body and the intake cup.

Make the clamp screws upward, then set the

intake hose and fix it by tightening the screws.

Torque: 1.96～2.94N･m (20～30kgf･cm)

Engine Cover

Muffler

Muffler Gasket

Fuel

Tank

Engine Cover

Intake Hose Intake Cup

Air Cleaner Body

Clamp Screws (2)

Screws (5)

TP5x 25L (T27)

-３４-


7-12 Frame Installation

1. Match the convex portions of the upper damper

and the convex portions of the volute cover as

shown. Set the washer for falling prevention and

securely attach the upper damper to the volute

cover.

Torque: 3.92～4.94N･m (40～50kgf･cm)

2. Insert the stud bolts of the lower dampers into

the frame and press the upper damper firmly to

the frame side.

3. Tighten the mounting nuts of the lower dampers.

Torque: 3.92～4.94N･m (40～50kgf･cm)

4. Tighten the mounting screws of the upper

damper.

Torque: 2.45～3.43N･m (25～35kgf･cm)

NOTE:

Set the guide of the volute case inside the

guard net.

Washer

Upper Damper

Volute Cover

Convex Portion,

Upper Damper side

Upper Damper

Volute Cover

Frame

Nuts (2)

Guide

Guard Net

Bolt M5x 40L (T27)

Convex Portion,

Volute Case side

Screws (2) TP5x 16L (T27)

-３５-


7-13 Fuel Pipes Installation

When installing the fuel pipes, align the “○”mark

of the pipe grommet and the “△” mark of the fuel

tank.

NOTE:

If it is not aligned to the “○” and “△” marks,

the fuel pipe may be twisted and the fuel

filter may not be in the proper position.

Make sure that the protruding length from

the grommet is the specified dimension.

If protrudes too much or extends too little,

pipe bending and/or poor fuel filter

response may occur.

Connect the return pipe and the suction pipe

securely to the carburetor, and fix the return pipe

firmly with the clip.

Pipe Grommet

長

す

ぎ

た

り

、

短

す

ぎ

た

り

す

る

と

、

フ

ィ

ル

タ

ー

の

追

従

性

が

悪

く

な

る

恐

れ

が

あ

り

ま

す

。

長

す

ぎ

た

り

、

短

す

“○” Mark

Fuel Tank

長

す

ぎ

た

り

、

短

す

ぎ

た

り

す

る

と

、

フ

ィ

ル

タ

ー

の

追

従

性

が

悪

く

な

る

恐

れ

が

あ

り

ま

す

。

95mm

長

す

ぎ

た

り

、

短

す

ぎ

た

り

す

る

と

、

フ

ィ

ル

タ

ー

の

追

従

性

が

悪

く

な

る

恐

100m

m

長

す

ぎ

た

り

、

短

す

ぎ

た

り

す

る

と

、

フ

ィ

ル

タ

ー

の

追

従

性

が

悪

く

な

る

“△” Mark

Fuel Tank

長

す

ぎ

た

り

、

短

す

ぎ

た

り

す

る

と

、

フ

ィ

ル

タ

ー

Fuel filter

Return pipe (yellow)

長

す

ぎ

た

り

、

短

す

ぎ

た

り

す

る

と

、

フ

ィ

ル

タ

ー

の

追

従

性

が

悪

く

な

る

恐

れ

が

あ

り

ま

す

。

Suction Pipe (black)

Pipe Grommet

長

す

ぎ

た

り

、

短

す

ぎ

た

り

す

る

と

、

フ

ィ

ル

タ

ー

の

Suction Pipe (black)

Return pipe (yellow)

長

す

ぎ

た

り

、

Clip

長

す

ぎ

た

り

、

短

す

Carburetor

長

す

ぎ

た

り

、

短

す

ぎ

た

り

す

る

と

、

-３６-


7-14 Switch Cords and Cable Installation

Securely fix the switch cord and the throttle cable

with the clamps as shown.

Torque: 1.96～2.94N･m (25～30kgf･cm)

7-15 Elbow Installation

Apply grease to the O-ring of the elbow.

Loosen the bolts of the elbow mounting portion of

the volute case. Insert the elbow between the

volute case and the volute cover, tighten the

loosened bolt and attach the elbow to the volute

case.

Torque: 0.49～0.98N･m (5～10kgf･cm)

NOTE:

If the bolt is tightened too much, the elbow will

not rotate smoothly.

Volute Case

Volute Cover

Elbow

Clamp

Throttle

Cable

Switch Cord

Clamp

Screws (2) TP5x 14L (T27)

Bolts (2) M5x 70L (T27)

O-ring

-３７-


7-16 Recoil Starter Assembly

1. Wind up the return spring while winding it inside

as shown.

NOTE:

Wind up the return spring so that the outer

diameter becomes 65 mm or less.

2. Set the return spring which has been wound to

the recoil case.

NOTE:

Securely insert the spring hook (a) of the

return spring into the groove of the recoil

case. Make the gap of the spring hook (b)

and the boss of the recoil case about 2mm.

Apply grease to the boss.

Grease:

Cold-resistant grease No. 2 or equivalent

3. Insert a rope through the reel as shown in the

figure and tie a knot at position of about 30mm

from the end of the rope. Push the knot of the

rope in the groove of the reel.

Round the end of the rope and push it into the

groove of the reel with the knot.

Reference:

This model uses rope size ofφ3.8×750-

850mm

30mm

Rope Reel

Knot

Groove

Hook (a) Boss

Hook (b)

2mm Recoil Case

Return Spring

Wind up.

65 mm or less

-３８-



4. Wind the rope to the reel counterclockwise, and

hang the rope to the notch of the reel.

However do not wind up all the rope, leave about

35 to 40cm from the notch of the reel.

5. Apply grease to the inner surface of the reel.

Pass the rope through the guide of the recoil

case, and insert the reel with the wound rope to

the boss of the recoil case. When inserting the

reel, engage the spring hook (b) to the groove

under the reel.

Grease:

Cold-resistant grease No. 2 or equivalent

Reference:

The groove on the bottom side of the reel is

positioned between the notch and the knot of

the rope.

6. Lightly turn the reel clockwise, and make sure

the groove and the spring hook (b) are engaged.

If engaged correctly, the reel will return to its

original position by the force of the return spring.

7. Set the washer and damper spring in the reel,

and install the cam plate with a mounting screw.


Notch

Reel

Rope

About 35 to 40cm

Screw

Cam plate

Damper Spring

Washer

Washer

Reel

Reel

リール下の溝

Guide

Boss Hook (b)

Wind up counterclockwise.

Groove

Rope

-３９-



8. Pass the rope through the knob and the cover

and make a knot at the end of the rope.

9. Push the knot of the rope into the cover and

insert the cover into the knob.

10. Pull the rope up into the notch in the reel, turn

the reel 4 to 5 times counterclockwise and hold

the reel with your thumb.

11. Detach the rope from the notch of the reel,

stretch it with the knob, and release the thumb

and slowly wind up the rope to the reel with the

spring tension.

NOTE:

When the rope is fully pulled out, make

sure that the reel rotates 1 to 1-1/2

counterclockwise.

If the reel rotates 1-1/2 or more, increase by

1 the number of winding of the rope.

If the reel dose not rotation 1 time, reduce

by 1 the number of winding of the rope.

Knot

Knob Cover

Rope

Rope

Reel

Notch

Reel Rope

How to knot a rope： Hold this portion.

-４０-


7-17 LHD-Throttle Lever Set Assembly

1. Cover the engine switch with the cap, pass the

switch cords through the arm cover.

2. Place the switch cord connectors on the L shape

side of the throttle cable and pass them through

the corrugate tube.

3. Pass the corrugated tube through the guide hole

of the throttle arm.

4. Align the stopper portion of the throttle lever at

the lever operation range (A) of the throttle arm

and insert the throttle lever in the hole of the

throttle arm.

5. Set the wave washer and the lever plate to the

throttle arm, and tighten the mounting bolt.

Throttle lever operating torque:

0.86～1.18N･m (8.7～12kgf･cm)

Cap Engine Switch

Arm Cover

Corrugate Tube

Switch Cords

Throttle Cable

Wave Washer

Throttle Lever

Throttle Arm Lever Plate

Stopper

(A)

Connectors

Corrugated Tube

Guide Hole

Throttle Arm

Bolt M5x 22L (T27)

Throttle Lever

-４１-


7-17 LHD-Throttle Lever Set Assembly

6. Set the throttle lever to the wide open throttle

position. Connect the contact plate to the

terminal of the switch cords (black) and set it in

the throttle arm. Push the contact plate firmly into

the guide of the throttle arm.

7. Attach the switch cords along the guide groove

of the throttle arm as shown.

8. Pull the wire of the throttle cable and connect the

wire end to the lever plate.

9. Attach the throttle cable end to the groove of the

throttle arm.

10. Push the switch cords into the groove of the

throttle arm and set the stopper as shown.

11. Attach the arm cover to the throttle arm with the

mounting screws.


12. Attach engine switch to arm cover.

Terminal

Contact Plate

Throttle Wire

Wire End

Contact Plate

Throttle Lever

Wide open throttle position

Switch Cords

Stopper

Engine Switch

Switch Cords

Screw (2)

TPM4x 20L (T27) Engine Switch

Throttle Arm

Lever Plate

Throttle Cable End

Arm Cover

-４２-


7-18 RHD-Throttle Lever Set Assembly

1. Make an alignment line at 2.2 mm from the end

of the shaft.

2. Set the control lever to the left handle half, and

install the rubber spring and the washer while

inserting the shaft. Apply grease between the

washer and the lock washer.

3. Push the lock washer straight to the shaft and

attach the control lever to the left handle half.

NOTE:

When pushing the lock washer, align the

projections of the lock washer with the

alignment line marked in step 1.

If the lock washer is set inside of the

alignment line position, the operation of

the control lever may become too heavy.

The lock washer may need to be pushed more again when control lever returns automatically during operation. Control lever operating torque:

0.41～0.52N･m (4.2～5.3kgf･cm)

4. Match the color of the switch cords and the

shape of the contact plates as shown and

connect the terminals to the contact plates

5. Place the contact plates and the switch cords on

the left handle half.

NOTE:

Set the clearance at the tip of the contact

plates to 1 mm or more.

When wiring the switch cords, place the

red cord to the handle side and press them

into the guide groove.

Washer Rubber Spring

Shaft Control Lever

2.2mm

Alignment Line

Shaft

Left Handle Half

Lock Washer

Alignment Line

Lock Washer

(Projection) Shaft

Black- Switch Cord

Red-Switch Cord Contact Plate (Red side)

Contact Plate (Black side)

1mm or more

Red-Switch Cord Guide Grooves

Guide Groove

Contact Plates

-４３-


7-18 RHD-Throttle Lever Set Assembly

6. Set the control lever to the wide open throttle

position. Hook the end of the spring to the

contact plate (black cord side), set it on the

handle, and attach the retainer with the mounting

screw.

Torque: 0.3～0.5N･m (3.1～5.1kgf･cm)

NOTE:

After installing the retainer, operate the

control lever from the idling position to the

engine stop position and check that the click

sounds.

7. Set the control lever to the engine stop position.

Connect the wire end of the throttle cable to the

throttle lever and set them to the handle.

Attach the lever spring to the throttle lever.

Check the link between the throttle lever and the

control lever, make sure that the control lever can

move fully.

NOTE:

Make sure that the tip of the lever spring is

hooked under the wire end connecting portion

of the throttle lever

Attach the throttle cable end to the groove of the

handle.

8. Set the corrugated tube in the groove of the left

handle half and install the light handle half with

the mounting screws.


9. Check the control lever dose not return from the

wide open throttle position automatically.

Spring

Contact Plate (Black cord side)

Retainer

Retainer

Control Lever

Wire End

Throttle Wire

Throttle Cable End

Throttle Lever Throttle Lever

Groove

Screw TPM3x 6L

Screw (2)

TPM4x 18L (T27) Right Handle Half

Light Handle Half

Corrugated Tube

Control Lever

Control Lever

Lever Spring

② Idling position

① Engine stop position

③ Wide Open Throttle position

③

①

①

②

③

-４４-

8. Carburetor

8-1 Technical Data

Items Specifications

Blower Model EBZ7500 EBZ8500

Model WYA-236A WYA-237A

Part Number 581 15 61-01 581 17 70-01

Limiter Cap ○ ○

Basic Adjustment Turns※1 L-needle (Low Speed Mixture)

※2 14 14 - 1/2

H-needle (High Speed Mixture)※3 1- 3/4±1/2 2 - 1/4±1/2

Metering Lever height mm 1.5 ±0.16 ←

Venturi diam. Lead air φmm 13.50 ←

Air-fuel Mixture φmm 12.20 ←

Bore diam. Throttle valve side φmm 12.2 ←

Choke valve side φmm 14.5 ←

Inlet Valve Opening pressure kgf/cm2（kPa） 1.3～2.3 （127～226） ←

Reseating pressure kgf/cm2（kPa） 0.6～1.6 （59～157） ←

Idling speed range rpm 1,800～2,200 1,900～2,100

No-load maximum speed range rpm 6,900～7,300 7,200～7,300

Rich down range rpm 600～800 700

※1: Basic adjustment turns is reference value.

※2: Loosen then tighten

※3: Tighten then loosen

Required Tools

① Carburetor Cleaner

② Pressure Gauge

3699-90211

③ Limiter Cap Tool

848-8W9-0080

④ Driver (Needle adjustment)

H531 00 4863

⑤ Tachometer

PET-1000

3699-90537

⑥ Tachometer

PET-2000DXR

3699-92470

M2 left-threading

-４５-

8. Carburetor

8-2 Description

If the carburetor is malfunctioning, adjust the fuel and inspect the damage of the component parts.

If engine speed is not stable and has bad acceleration, adjust the mixture needles according to the item “8-4

Adjustment”.

H-needle

L-needle

Gasket

Pump Diaphragm

Inlet Valve

Gasket

Metering Lever

Limiter Cap

Idle Adjustment Screw

Limiter

Cap

Body Assy.

Metering Diaphragm

Air Purge Body

Priming Pump

Pump Cover


Adjustment of the idle engine speed.

Turn Direction Speed

Clockwise Increases

Counterclockwise Decreases

L-needle

Adjustment of the low and medium engine

speed.

Turn direction Fuel

Clockwise Leaner

Counterclockwise Richer

H-needle

Adjustment of the high engine speed.

Turn direction Fuel

Clockwise Leaner

Counterclockwise Richer

Throttle Valve

-４６-

8. Carburetor

8-3 Inspection

1) Metering Diaphragm

Check the metering diaphragm for damage and

stiffness. If necessary, replace it with a new

one.

Check that the convolution height of metering

diaphragm does not become flat. When

convolution height is flat, replace the metering

diaphragm with a new one.

2) Pump Diaphragm

Check the pump diaphragm for damage and

stiffness. If necessary, replace it with a new

one.

In particular, if the pulse receiving portion and

valve portions of the diaphragm are stiff,

replace it with a new one.

3) Inlet Valve Leaking Test

Connect the pressure gauge (special tool) to

the inlet port of the carburetor body assy. Apply

pressure to the inlet valve and read the

opening pressure and the reseating pressure.

Opening pressure:

1.3～2.3kgf/ cm2 (127～226kPa)

Reseating pressure:

0.6～1.6kgf/ cm2 (59～157kPa)

If the reading is out of the specified standard,

check the item "4) Metering Lever and Inlet

Valve".

Pressure gauge

Air Pump

Carburetor Body Assy.

This portion not flat.

Convolution Height

Metering Diaphragm

Valve Portions

Pump Diaphragm

Pulse Receiving Portion

-４７-

8. Carburetor

8-3 Inspection

4) Metering Lever and Inlet Valve

Measure the metering lever height using a

depth gauge or scale.

Specified standard: 1.5±0.16mm

If the reading is out of the specified standard,

repair the metering lever or replace it with a

new one.

Check the wear of the contact portion of the

metering lever and the metering diaphragm. If

necessary, replace them with new parts.

Check the lever shaft, and if it is rusted replace

it with a new one.

Remove the inlet valve and check for dirt,

sludge, rusting and/or step-wear. Replace the

inlet valve if a beveled edge is found on the

rubber tip.

Inspect the clogging of the fuel passage in the

carburetor body and make sure there are no

dirt on the pump cover. If necessary, dip the

carburetor body and the pump cover in

gasoline for about 10 minutes, or clean them

using carburetor cleaner.

When setting the spring, be careful not to bend

it.

5) Screen

Inspect the screens for clogging, be sure to clean

if the dust is adhered.

Body Assy.

Metering Lever 1.5±0.16mm

Body

Assy.

Valve Seat

Lever Shaft

Inlet Valve

Check of the wear.

Metering Diaphragm

Step-wear

Not-good

Screen

Clogging

Bending of the spring.

-４８-

8. Carburetor

8-3 Inspection

7) Main Check Valve

Make sure to check the main check valve in

case fuel is not supplied though the priming tic

when operated.

Press the vinyl pipe (inner diameter:φ5mm)

against the main check valve and blow and

suck with mouth.

[A]: Stop by blowing

[B]: Open by sucking

Main check valve has no failure.

In case of failure, soak the body assy. into

gasoline for about 10 minutes and repeat

blowing and sucking several times. If this is not

successful, replace the body assy.

NOTE:

Do not clean the main check valve with

compressed air. If the main check valve is

cleaned by compressed air, it may not

function properly.

8) H-needle

Remove the limiter cap with the limiter cap tool

(see page 50).

Remove the H-needle, check the wear and

damage of the tip and screw portions and if

necessary replace it with a new one.

Clean the clogging of the fuel passage of the

carburetor body. When cleaning, remove the

throttle valve and spray the carburetor cleaner

from the main nozzle side and the H-needle

mounting hole side.

NOTE:

In this carburetor, the fuel passage at the

tip of the needle is narrower than the

conventional carburetor. Therefore, to

prevent clogging, clean the passage

securely.

When using a fuel with a high mixing ratio

of oil, clogging is likely to be caused by oil

sludge and dust, so we recommend mixing

ratio gasoline 50 : FD registerde oil 1.

Plastic Pipe

Main Check Valve

H-needle

O-ring

Carburetor

Cleaner

Main

Nozzle

Body

H-needle Mounting Hole

Body Assy.

[A] [B]

-４９-

8. Carburetor

8-3 Inspection

9) Gaskets

When assembling the new metering diaphragm

and the new pump diaphragm, be sure to replace

the gasket with new parts at the same time.

10) Throttle Valve

Check the wear of the plunger contact surface

of the throttle valve.Carefully move the thin tip

screwdriver along the slope of the plunger

contact surface and inspect for any grooves or

scratches where the tip of the screwdriver

catches. If there are grooves, replace the

throttle valve assy. with a new one..

11) Jet Needle

Check that no wear exists on the jet needle.If

there are signs of vertical linear flaws or wear,

replace the throttle valve assy. with a new one.

NOTE:

Even small damage affect fuel flow.

Jet Needle

Damage Wear

Throttle Valve Assy.

Contact Surface Plunger

New Gasket

New

Pump

Diaphragm

New gasket

New Metering Diaphragm

-５０-

8. Carburetor

8-4 Adjustment

1) Limiter Cap Removal

Insert the threaded portion of the limiter cap tool

(special tool) into the hole of the throttle valve

and screw it counterclockwise while pressing it

against the limiter cap. Remove the L-needle

side limiter cap from the throttle valve by pulling

the limiter cap tool. Remove the H-needle side

limiter cap in the same way as the L-needle side

limiter cap.

NOTE:

If it is difficult to screw in the limiter cap tool,

firmly press the tool while screwing. When

threads are completely meshed, pull it out in

one stroke. If cap is damaged and stays in

the hole, use a pick type tool to remove it.

2） Initial Start Settings

① Turn the Idle adjustnment screw

counterclockwise (CCW) until its tip just

touches throttle valve stop, then turn it

clockwisely (CW) to the position where the

engine speed gets slightly higher.

② Turn the L-needle counterclockwise (CCW)

completely out until a “clicking sound” is

heard.

③ Then turn the L-needlein clockwise (CW) at

Basic Adjustment Turns.

NOTE:

Do not tighten the L-needle more than the

Basic Adjustment Turns. Tightening too

much may damage the needle spring and

L-needle.

Models Basic Adjustment Turns

WYA-236A (EBZ7500) 14

WYA-237A (EBZ8500) 14- 1/2

④ Turn the H-needle clockwise (CW) until very

gently seated.

⑤ Then turn the H-needle counterclockwise at

(CCW) Basic Adjustment Turns.

Model Basic Adjustment Turns

WYA-236A (EBZ7500) 1- 3/4±1/2

WYA -237A (EBZ8500) 2- 1/4±1/2

④

⑤

H-needle

② Driver

(Tip width: 2 mm)

③

L-needle


①

Limiter Cap Tool

(M2 left-threading)

L-needle

Limiter Cap

Driver

(Tip width: 2 mm)

-５１-

8. Carburetor

8-4 Adjustment

3) Warm-up

Standard pipe and nozzle must be installed

properly. Start the engine and alternate three

times between the idling state (10 seconds) and

wide open throttle (60 seconds).

4) Low Speed Mixture Needle Adjustment

① Turn the L-needle clockwise (CW) or counter-

clockwise (CCW), to adjust so that the engine

speed is the maximum speed.

② Adjust the engine speed at Peak Idling rpm

with the idle adjustment screw.

Models Peak Idling (rpm)

WYA-236A (EBZ7500) 2,700±200

WYA-237A (EBZ8500) 2,700±100

③ Set the engine speed at 2,000±200 rpm by

turning the L-needle counterclockwise (CCW).

Models Rich Down (rpm)

WYA-236A (EBZ7500) 600～800

WYA-237A (EBZ8500) 700

NOTE:

In order to accurately measure the engine

speed, measure every time the L-needle is

adjusted about 10 seconds after the

engine speed stabilizes.

Rich Down:

Adjust the L-needle to a slightly richer

mixture in order to maintain a stable idling

speed and get a good acceleration.

①

L-needle

②


③

Target RPM

Rich Down

Co

ns

um

pti

on

L/h

2,000±200rpm Peak Idling

Engine speed (rpm)

-５２-

8. Carburetor

8-4 Adjustment

5) High Speed Mixture Needle Adjustment

Accelerate engine to wide open throttle, adjust the

engine speed at Maximum Speed rpm by turning

the H-needle clockwise (CW).

Models Maximum Speed (rpm)

WYA-236A (EBZ7500) 7,100±200

WYA-237A (EBZ8500) 7,250±50

NOTE:

If the engine speed is too high,

acceleration failure and output will

decrease.

The ignition coil is digital control misfire

type, and when the engine speed is too

high, it may not be possible to display with

the tachometer.

6) Plug Installation

Push the plug (No.1881-81160) firmly into the

holes of the L-needle and H-needle using the

straight side of the limiter cap tool (special tool).

H-needle

Plug

Plug

-５３-


9-1 Standards and Service Ability Limit

Maintenance Item Unit EBZ7500 EBZ8500 ※1

Measuring Procedure

Standard Limit Standard Limit

Cylinder

Compression pressure kgf/cm² （kPa）

8.4 5.6 8.4 5.6 CPG Cylinder/ Piston ring Replace.

Bore mm φ47.5 ※2 φ51 ※2 CG Expose of base

metal: Replace.

Piston

Piston skirt diameter mm φ47.454～φ

47.474 φ47.37

φ50.98～φ50.91

φ50.81 MM Replace.

Piston ring

groove width

Top mm

1.23 1.3 ← ← TG Replace.

2nd 1.21 1.3 ← ←

Piston pin hole mm φ12.005 φ12.045 ← ← CG Replace.

Clearance between

piston and cylinder mm

0.056～0.096

0.22 0.07～0.11

0.22 MM CG

Piston

Replace.

Clearance

between piston

groove and

piston ring

Top

mm

0.06～0.1 0.15 ← ←

TG Replace.

2nd 0.04～0.08 0.15 ← ←

Fitting between piston

pin and piston pin hole mm

0.005～0.021

0.05 ← ← MM CG

Replace.

Piston Ring End gap at cylinder skirt mm 0.15～0.35 0.6 ← ← TG Replace.

Width mm 1.2 1.1 ← ← MM Replace.

Piston Pin Diameter mm φ12 φ11.98 ← ← MM Replace.

Connecting Rod

Small end bore mm φ16 φ16.03 ← ← CG Replace.

Parallelism of large/ small

end bores 0

0.15/

100※3 ← ←

Mandrel DG

Replace.

Crankshaft

Diameter at

main bearing

MAG mm

φ16 φ15.95 ← ← MM Replace.

PTO φ16 φ15.95 ← ←

Diameter at oil seal

(MAG，PTO) mm φ16 φ15.9 ← ← MM Replace.

Eccentricity mm 0 0.06※4

（@ 6） ← ←

DG Center Support

Repair or replace.

Width between crank

webs mm 31

30.9～

31.1 ← ← MM Repair or replace.

Axial Play mm 0.071～0.369

0.5 0.057～0.383

0.5 TG Replace.

Main Bearing －－ ※5 － ※5 － Replace.

※1 Meaning of abbreviations

CG：Cylinder Gauge/ MM：Micrometer/ DG：Dial Gauge/ TG：Thickness Gauge/ CPG：Compression gauge

※2 Peel off of plating or expose of base metal.

※3 length of the 100m, 0.05 or less

※4 Points from the crank web of 6mm

※5 Flutter, irregular noise generated

-５４-


9-2 Tightening Torques

Tightening Item Thread size

(mm)

Tightening Torque

N・m (kgｆ・cm)

Engine

Spark Plug M10S×1.0 9～12 (90～130)

Muffler Upper: M6×30L

Lower: M6×16L 8～12 (80～120)

Diffuser M4×8L 2～3 (20～30)

Cylinder M5×22L 6～9 (60～90)

Cylinder Plate M5×8L 3～4 (30～40)

Crankcase M5×30L 6～8 (60～80)

Insulator M5×27L 4～6 (40～60)

Intake Cup/ Carburetor M5×60L 3～4.5 (30～45)

Recoil Starter M5×16L

(Apply 3M-2353 12mm) 3～4.5 (30～45)

Starter Pulley ━ 2.9～3.9 (30～40)

Rotor M10×1.0 (Hex nut) 25～35 (250～350)

Ignition Coil M4×22L 2.5～4 (25～40)

Coupling M10×1.0 (Hex nut) 25～35 (250～350)

Fuel Tank 5×12L 2.5～3.5 (20～35)

Engine Mount M6×50L 10～12 (100～120)

Guard Net/ Volute Cover/ Volute Case/ Engine Cover/ Cleaner 5 (1.81P-tight)×25L 3～4 (30～40)

Fan M6×26L 10～14 (100～140)

Upper Damper Left and right M5×16L (2) 2.5～3.5 (25～35)

Center M5×40L (1) 4～5 (40～50)

Lower Damper M6×1.0 (Hex nut) 4～6 (40～60)

Throttle Arm M5×16L 2.5～3.5 (25～35)

-５５-

10. Troubleshooting

10-1 Engine does not start

Remove the spark plug from the cylinder. Put the spark plug on the outside of the cylinder. Pull the recoil starter knob, and

check whether sparks occur in the spark gap or not.

Trouble Probable Cause Countermeasure

No spark in the spark plug.

Spark plug

1. Wet spark plug electrodes Make them dry.

2. Carbon deposited on the electrodes Clean or replace.

3. Smolder of the electrodes Clean or replace.

4. Insulation failure by insulator damage Replace.

5. Improper spark gap Adjust to 0.6 to 0.7mm or replace.

6. Burn-out of the electrodes Replace.

Ignition coil

1. Ignition coil inside failure Replace.

2. Air gap is not proper Adjust to 0.3mm.

3. Plug cap and cap spring are damaged Replace.

4. Damage cord sheath or disconnection Repair or replace.

Switch

1. Switch is OFF ON the switch.

2. Switch failure Replace.

3. Primary wiring ground Repair or replace.

Sparks appear in the spark plug.

Compression and fueling are normal

1. Over sucking of fuel Drain excess fuel.

2. Too rich fuel Adjust or replace carburetor.

3. Overflow Adjust or replace carburetor.

4. Clogging of the pre-filter and the paper filter

Pre-filter Wash with hot water containing neutral detergent and dry.

Paper filter Clean with air blow or replace.

5. Incorrect fuel Change with proper fuel.

Fueling normal but poor compression

1. Spark plug is loosened Retighten.

2. Cylinder wall and piston ring are worn or damaged Replace.

3. Gas leakage from cylinder and crankcase Replace gasket and reassemble.

No fuel supply

1. Carburetor improper adjustment Readjust.

2. Clogged carburetor Disassemble and clean.

3. Clogged fuel filter Clean or replace.

4. Clogged or damaged fuel pipes Clean or replace.

5. Gas leakage from oil seal of the crankcase Replace.

-５６-

10. Troubleshooting

10-2 Engine stop during operation


Suddenly stopped.

1. Switch is OFF ON the switch.

2. Plug cap disconnect Connect properly.

3. Switch cord or high tension cord sheath worn out

Replace.

4. Air gap is not proper Adjust to 0.3mm

5. Ignition coil inside failure Replace.

6. Engine seizure Overhaul and replace damaged parts.

7. Clogged breather Clean.

Gradual speed reduction and stopped.

1. Lack of fuel Refill.

2. Clogged carburetor Disassemble and clean.

3. Water mixed with fuel Drain and apply new fuel.

Revolution rises suddenly and stops.

1. Lack of fuel Refill.

2. Clogged breather Clean.

3. Clogged carburetor Clean.

10-3 Engine cannot be stopped


Overheating

1. Lean fuel Adjust or replace carburetor.

2. Cooling passage clogged with dusts Clean.

3. Cylinder fin clogged with dusts Clean.

4. Improper fuel Change with proper fuel.

5. Carbon deposited inside of combustion chamber

Clean.

6. Spark plug electrode red hot Clean thoroughly and adjust spark

gap to 0.6 to 0.7mm.

Ignition coil 1. Ignition coil inside failure Replace.

Switch 1. Switch failure Replace.

2. Cord failure Replace.

-５７-

10. Troubleshooting

10-4 Lack of output power or unstable revolution


Compression is normal and no misfire.

1. Air is entering at fuel pipe joints, Secure connections.

2. Air is entering at crack or pinhole of fuel pipe.

Replace.

3. Air is entering at insulator and carburetor mounting portion

Replace gasket and retighten.

4. Air is entering at oil seal Replace.

5. Water mixed with fuel Drain/ clean and apply new fuel.

6. Piston is starting to seize Filing of seized surface with fine files or replace.

7. Muffler clogged with carbon Clean.

Overheating

1. Lean fuel Adjust or replace carburetor.

2. Cooling passage clogged with dusts Clean.

3. Cylinder fin clogged with dusts Clean.

4. Improper fuel Change with proper fuel.

5. Carbon deposited inside of combustion chamber

Clean.

6. Spark plug electrode red hot Clean thoroughly and adjust spark gap to 0.6 to 0.7mm.

Others

1. Poor fuel quality Replace with clean fuel.

2. Clogged fuel filter Clean or replace.





10-5 The amount of the wind is weak


Good compression but cannot reach the required revolutions at full throttle





3. Carburetor failure Maintenance or replace.

-５８-

10. Troubleshooting

10-6 Others


Poor fuel consumption

Clogging of the pre-filter and the paper filter



ebz7500/ 8500 workshop manual

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