jetting advice

I have a 02 426 and just put a fmf powerbomb header and

"Q" silencer on. I ordered the FMF jet kit. I installed the 170 main and the fmf needle at clip position 2. The bike now has a serious hesitation for the first 1/4 throttle. It runs great at all other throttle positions. the fmf directions said 1 3/8 turns for the stock and 3 for the aftermarket. I have tried everything from 1-4. It is worse at 1 3/8. I am new to the dirt bike scene and could use some advice. I appreciate anything anyone has to offer. Thanks

Your first 1/4 throttle is coming off the pilot jet. If you didn't change it, that's probably where your problem is. Mine came stock with a 42 pilot, and I had to go to a 45 just to get it running right even with as hot as its been.

Go up a size on the pilot jet and readjust the fuel screw then and see how it runs.

Here's a link that explains all of this really well.

http://www.atlanticmx.com/archives/00000135.shtml

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