Dying Coil.... How to tell?

[Derrick Adams]

I felt this post was neccessary for us guys that don't know.

Discussion in another post has brought up this question from me. How do you know when a coil is going out?

My bike failed to start a couple weeks ago (it was 20 degrees out) Turns out there was very weak spark. You could hear it but not see it. When I went out to work on it earlier this week, it had great, visible spark again.

The other issue is a very rich idle circuit now. (may or may not be related) but it refuses to idle and is bellowing smoke from the exhaust. Could a weak coil cause this as well?

[TimSr]

Coils rarely go out (except on Taiwan made mini quads) but when they do, you either lose sprk, or get intermittent loss of spark whcih means popping sputtering and backfiring. I have never, ever seen a weak spark as the result of a spark plug coil problem, though I have heard of some of the 4 stroke Hondas having problem the pickup coil or its gapping.

If you are hearing a spark and not seeing it, my first guess is that the spark is working fine, just not jumping across the plug gap, but somewhere else. This can be from a crack in the plug wire, or an insulation probelm with the plug boot. You cant check insulation problems with a Volt Meter, either. The easiest way to check for such a problem is to fire it up, get it warmed up and running good, and spray some water directly on the coil and plug wire while its running. If there is an insulative breakdown, you will immediately know it.

[70binder]

Coils rarely go out (except on Taiwan made mini quads) but when they do, you either lose sprk, or get intermittent loss of spark whcih means popping sputtering and backfiring. I have never, ever seen a weak spark as the result of a spark plug coil problem, though I have heard of some of the 4 stroke Hondas having problem the pickup coil or its gapping.

If you are hearing a spark and not deeing it, my first guess is that the spark is working fine, just not jumping across the plug gap, but somewhere else. This can be from a crack in the plug wire, or an insulation probelm with the plug boot. You cant check inuslation problesm with a Volt Meter, either. The easiest way to check for such a problem is to fire it up, get it warmed up and running good, and spray some water directly on the coil and plug wire while its running. If there is an insulative breakdown, you will immediately know it.


dont touch any of the ignition parts when you do that :naughty: unless you want a nice 40,000 volt zap :p