01 yz 426 backfiring and cutting out on acceleration


Fairly new to 4 strokes so any help is appreciated.

I've recently purchased a 01 yz 426, the problem I have is when I try to rev the engine, it just backfires, pops, and cuts out, at idle the bike is fine, and I have no trouble starting it hot or cold, I have replaced the sub wiring harness and removed the carb and cleaned it. But the problem still exists!

Please help!!!

Sounds like jetting problems.

Hi, Thanks for the reply, What would I need to do to solve this, my knowledge is fairly basic,


Check that the small wire at the bottom of the ignition coil is properly in place. If this comes loose, it can cause problems like you describe.

Thanks dee cee I'll try that, I've also noticed that the new plug I have installed is looking a little worse for wear ( black with carbon ) after only idling and revving the bike a couple of times, the bike seems ok till anything over 1/4 throttle, from reading the manual and seeing the state on the plug, I'm guessing that the bike could be running rich,

so I'm thinking I need to lean it out on the jet needle, this would mean stepping the clip down one notch or more, I'm a little hesitant to start playing with the jetting as I'm no expert in carbs.... So I was wondering what everybody thought before I do so.


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