STIHL 029, 039 39

5.1.2 Ignition Module 5.1.2.1 Ignition Timing 5.1.2.2 Removing and Installing

Top:1 = Spark plug terminal2 = Ignition lead retainer3 = Groove

Bottom:1 = Lead retainer2 = Short circuit wire

1 = High voltage output2 = Connector tag

The ignition module accommodatesall the components required to controlignition timing. There are twoelectrical connections on the coilbody:

1. the high voltage output2. the connector tags for the short

circuit wires

Accurate testing of the ignitionmodule is only possible withsophisticated test equipment. Forthis reason it is only necessary tocarry out a spark test in the work-shop. A new ignition module must beinstalled if no ignition spark isobtained (after checking that wiringand stop switch are in goodcondition).

- Remove handle housing - see8.1.1.

- Pull terminal off the spark plug.

- Remove the ignition lead fromthe retainer and groove on thecover.

- Pull the short circuit wire off thetag on the ignition module andremove it from the lead retainer.

Ignition timing on the electronic(breakerless) magneto ignitionsystem is fixed at 2.4 mm (0.095")B.T.D.C. at 8,000 r.p.m. and is notadjustable.

However, in view of the permis-sible tolerances in the electroniccircuit, it may vary between 2.0and 2.8 mm (0.080" and 0.11 ")B.T.D.C. at 8,000 r.p.m.

Since there is no mechanical wear inthese systems, ignition timing cannotget out of adjustment. However, aninternal fault in the circuit can alter theswitching point in such a way that aspark test will still show the system tobe in order although timing is outsidethe permissible tolerance. This willimpair engine starting and runningbehavior.

STIHL 029, 039 40

Remove the ignition modulemounting screws.

Pull the ignition module forwardand push back the grommet onthe high voltage output.

Unscrew the ignition lead from thecontact pin and pull it out of theignition module.

If necessary, ease the peg of thelead retainer out of its seat andremove the retainer.

Note: Before fitting the ignition lead,pack the high voltage output withSTIHL multipurpose grease –see 12.2.

Important: Do not use graphitegrease (Molykote) or siliconeinsulating paste for this job.

- Push the grommet over theignition module's high voltageoutput.

- Place the ignition module inposition, fit screws but do nottighten down yet.

Important: Secure ground wire withupper screw and fit a washer on thelower screw.

- Slide the setting gauge betweenthe arms of the ignition module andthe flywheel magnets.

- Press the ignition module againstthe flywheel and tighten down themounting screws to a torque of4.8 Nm (3.5 Ibf.ft).

Important: Tighten the upperscrew first.

- Remove the setting gauge anduse a feeler gauge to check the airgap. It should be 0.15 - 0.3 mm(0.006 - 0.012").

Assembly of the remaining parts isnow a reversal of the disassemblysequence.

Setting gauge fitted betweenflywheel and ignition module

Top:Removing lead retainer

Bottom:Setting gauge 1127 890 6400

Top:Ignition module mountingscrews

Bottom:Pulling the unscrewed ignition leadout of ignition module

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5.1.3 Spark Plug Terminal

Top:Removing dust seal

Bottom:Pulling leg spring out of sparkplug terminal

- Fit the dust seal over the sparkplug terminal.

- Fit the terminal on the spark plug.Push the ignition lead into theretainer and groove on the cover.

- Fit the handle housing - see 8.1.1.

- Remove handle housing - see8.1.1.

- Pull terminal off the spark plug andremove the ignition lead from theretainer.

- Pull the dust seal off the sparkplug terminal and push it downthe ignition lead.

- Use a suitable pair of pliers togrip the leg spring and pull it outof the spark plug terminal.

- Unhook the leg spring from theignition lead and slip the sparkplug terminal and dust seal offthe lead.

- Slip the dust seal over theignition lead.

- Coat end of the ignition leadwith oil (about 20 mm/3/4").

- Fit spark plug terminal over theignition lead.

- Use suitable pliers to grip the end ofthe ignition lead inside the sparkplug terminal and pull it out.

Pinch the hook of the leg spring intothe center of the lead, i.e. about 10mm (3/8") from the end of the lead.

- Pull the lead back into theterminal so that the leg springlocates properly inside it (seeillustration).

Fitting dust seal

Top:Fitting the leg spring

Bottom:Correct position of leg spring in sparkplug terminal

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- Remove ignition module - see5.1.2.2.

- Pull the grommet off the ignitionlead.

- Pull the ignition lead out of thehole in the tank housing.

- Remove the spark plug terminal -see 5.1.3.

Removing the flywheel:

- Block piston with locking strip -see 3.2.

- Take out the fan housing mount-ing screws and remove the fanhousing.

- Cut new ignition lead to length(see parts list or cut to samelength as old lead).

Reassembly is a reversal of thedisassembly sequence.

Note: Use a pointed tool (awl orgimlet) to pierce the center of theother end of the ignition lead whichscrews into the module.

Note: Before fitting the ignition lead,pack the high voltage output withSTIHL multipurpose grease –see 12.2.

Important: Do not use graphitegrease (Molykote) or siliconeinsulating paste for this job.

5.1.5 Flywheel5.1.4 Ignition Lead

Top:Grommet

Bottom:Pulling ignition lead out oftank housing Piercing center of ignition lead

Top:Locking strip 0000 893 5902 incylinder

Bottom:Fan housing mountingscrews

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Top:Puller 1116 893 0800

Bottom:Puller fitted in position

1 = Flywheel2 = Magnet poles

- Inspect the condition of theflywheel. If you find any damage(e.g. cracks, broken fan blades),fit a new flywheel.

Installing the flywheel:

Important: Clean the stub of thecrankshaft and the flywheel hubbore with a standard commercial,solvent-based degreasant containingno CFCs. Fit the flywheel and tightenmounting nut to 27.5 Nm (20 Ibf.ft).

Assembly of the remaining parts isnow a reversal of the disassemblysequence.

Note: If the flywheel cannot beremoved by hand, screw the pulleronto the crankshaft stub, tap the endof the puller lightly with a hammer torelease the flywheel. Unscrew thepuller.

- Rotate the flywheel so that themagnet poles are opposite theignition module.

- Unscrew flywheel mounting nutfrom the crankshaft.

- Pull the flywheel off the crank-shaft.

Top:Flywheel mounting nut

Bottom:Removing the flywheel

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5.1.6 Short Circuit Wire/Ground Wire

5.1.7 Contact Spring

- Remove handle housing - see8.1.1.

Remove the flywheel - see 5.1.5.

- Remove the ignition module-see 5.1.2.2.

- Remove the ground wirefastening screw from thecylinder.

- Remove the air filter - see 11.1.

- Remove the switch shaft - see9.1.

- Pull the ground wire terminal offthe contact spring.

- Ease the contact spring out of itsseat in the handle housing.

Installation is a reversal of theremoval sequence.

- Pull the short circuit and groundwires out of the hole in the enginehousing.

- Pull the grommet off the shortcircuit and ground wires.

Installation is a reversal of theremoval sequence.

Top:Ground wire fasteningscrew

Bottom:Withdrawing short circuit wire andground wire Grommet

Top:Ground wire terminal

Bottom:Removing contact spring