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Q:

no spark at plug on chainsaw !!!

what can cause no spark at the plug on a chainsaw ? I have changed the plug but still no spark !!

Help !!!!!!

von
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1 Answer

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To troubleshoot this problem you need to remove the metal shroud on your chainsaw to expose the ignition wiring. Chainsaw engines, like most small engines, use a magneto to generate the high voltage that produces the spark. Once you have removed the shroud you will be able to inspect the magneto coil, its wiring, and the magnets imbedded in the flywheel.

The air gap between the flywheel magnets and the laminated pole piece of the magneto coil is critical. If the flywheel magnets have a buildup of dirt and sawdust on them clean them off. Remove any rust buildup using fine grit emery cloth, then check for spark at the sparkplug electrodes. Make sure the sparkplug is grounded against the engine when making this test. If there is still no spark, inspect the wiring coming from the magneto coil.

Look for a heavy black wire going underneath the flywheel. The presence of this wire indicates the presence of breaker points and a condenser behind the flywheel. Older chainsaws and other small engines had breaker points and condensers as part of the ignition systems just as older cars did. Points that are blocked with sawdust or other debris will keep the magneto from developing a spark as will a shorted or open capacitor. Pitted or burned breaker points will need to be replace and their gap set as specified in your users manual. Capacitors can be checked with an Ohmmeter but points and capacitors are relatively inexpensive and should be replaced anytime you pull the flywheel.

Check the ground wire on the magneto coil. A loose ground wire will prevent the magneto coil from generating a high voltage as well. Also, check for continuity through the kill switch with the Ohmmeter. A kill switch stuck in the closed position will short the magneto coil out and prevent it from developing spark voltage. Replace the kill switch if defective.

Check for continuity through the magneto coil, both primary and secondary windings with the Ohmmeter, an open winding will keep the magneto from developing spark voltage too. Also, check the coil wiring for chafing or cracking. If you find an open winding or damaged wires, replace the coil. Check your owner's manual for proper spacing between the magneto coil pole pieces and the flywheel magnets.
 

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