Motorcycle Repair: ATV 250, ceramic insulator, plug cap

Question
bike will only run when u jump a screw driver across from sparkplug wire to spark it fires rightup but wont fireup when u put spark wire on sparkplug   puzzeled??????????

Answer
Hi Craig,

You've described a problem known as ignition flash-over.   

One or more of the following are likely leaking electrical current: ignition coil lead, spark plug cap, and/or spark plug ceramic insulator.

You'll have to learn which is the defective part. Things to do:

Clean plug wire; remove dirt, oil, and moisture from wire.  Clean spark plug cap; remove dirt, oil, and moisture from interior and exterior of plug cap. Clean spark plug's exterior body.

Try another spark plug to quickly verify if the plug is the source.

If the problem still exists:

With the engine running, run a metal screwdriver shaft along the plug wire. You should see an arc in the area of the defect or leak.

Another technique is to water mist the lead and watch for an arc.


Replace defective parts and go riding.

Respectfully,
Mark Shively