Bad Coil or CDI?

I posted a topic a few days ago about my bike backfiring and running like it was fouling a plug after a couple hours of riding. Since I was riding at slow speeds and down long hills (keeping throttle closed to let engine brake) before it began to backfire, I assumed I was fouling a plug. I made it back to my truck after having to use the hot start to crank the bike (first time that I've ever had to use it). But after changing the plug, I didn't get very far before it died again (backfiring as I let off throttle). I am going to take the advice of you who replied to that post and clean the carb (am removing octopus so might as well). But a friend of mine is insisting that I have a bad coil or CDI. Would these symptoms be consistent with that problem? Any easy way to check them out?


I had a very similar problem on my 98 YZ400 a while back. Clark gave me some suggestions that I followed and the bike is running like a champ now. Specifically, he suggested doing the throttle shaft adjustment (directions in the Tech Section) and cleaning the accelerator pump and the rest of the carb really well. I also found a hairline crack in the lid of the carb which I fixed with some JB Weld. Not sure what the problem was, but like I said, the bike runs great now.

Check the original thread entitled:

Idle Issues/Major Backfiring

Good Luck!

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