'02 YZ426 jetting problem

1 reply to this topic

Posted January 20, 2010 - 05:55 PM


At Sea level, I installed a full exhaust system on my bike recently, a FMF Powerbomb and a FMF Q2. As well as a Dynojet kit, when I was playing with the fuel mixture I leaned it out quite a bit, but I still had a really bad bog.
I was told Accelerator pump timing needed to be adjusted, then I was also told to just leave the stock jetting and turn out the fuel screw and ill be fine. I've toyed with this carb quite a bit. Normally I can figure this kind of problem out pretty quick, but this carb has gotten the best of me.
I have hot cams and uni air filter if that helps at all. The people at dynojet arent too helpful in my situation.

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  • grayracer513

Posted January 20, 2010 - 07:47 PM


First, be sure you have realistic expectations. You can't really have a 426 that runs cleanly and right that will stand an instantaneous full throttle snap from idle no matter what. But if you are rolling the throttle in a realistic manner, and the bike still stumbles, first get the jetting right. Have a look here for ideas:


Once that's done, try this:


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