OK heres the deal. This is a quad that i worked on recently. It was a Chinese 110cc. It just died and the owner didnt know why. I timed the engine and it was retarded by 1 1/2" on the magneto. Installed new stator, cdi, and voltage regulator. Still same issue. See if you guys can figure out why the timing was so off.

 

Flywheel key is cut ..

 

nope. even if flywheel key was sheered, the timing light would still hit on F on flywheel. It would only throw out the cam to crank timing. good guess though

 

Since the ignition timing is not adjustable, I assume you mean you just checked the timing with a timing light. You say the timing is off by 1.5 inches. Usually errors of this sort are measured in degrees. Is the 1.5 inches measured on the outside circumference of the flywheel? If so, that would be a spark timing error of roughly 30 degrees. That's a lot. Are you sure you are measuring this right?

If the flywheel key was sheared I don't see how this would have any effect on the camshaft timing. The flywheel doesn't drive anything but magnets. And one of those magnets is what drives the ignition timing trigger coil that fires the CDI.

 

When he said timing was retarded 1 1/2 inches on the flywheel i was thinking cam timing mark on the flywheel.. The actual cam timing would still be right but the flywheel TDC mark would be off , and the bike wouldn't run because the ignition timing would be way out .. I had no idea the ignition is adjustable I didn't think it was adjustable on anything anymore ..

 

yes its out about 30 degrees. bad choice of wording. and the magnets in a magneto arent what trigger the timing. its the pickup coil that is located outside the magneto when it comes near the raised little square on the outside of the magneto that sets it off. it was firing 30 degrees after the little square passed by. i had never seen anything like this before now. it was a goofy chinese error in the wiring that made it do this. the cdi and voltage regulator were ground to each other but not the engine. this allowed it to run but very poorly. i took the wiring apart and soldered in a ground wire that connected the whole system and it ran perfecty

 

Wow! In a million years I would have never guessed that based on the symptoms. But now that you've nailed it, it sort of makes sense. Without any ground the trigger wouldn't work at all, but with an AC ground through the regulator and an output impedance of 150 ohms through the trigger coil, the trigger would occur but would be delayed.

I'm really impressed that you found this. I'm very glad you shared it.

 

yeah it was strange. i noticed a lot of chinese quads not running for no reason at all and hopefully this will help some others

 

Thanks for posting this info NewportHillClimber's, Im sure it will be a big help to someone..

Gotta admit I never would have come up with that answer..

 

I never would have come up with that answer too myself. Thanks by the way.