Requesting jetting recommendations

I’m installing a FMF PC-IV2 w/Powerbomb. Does anyone have jetting recommendations.

99 WR400 with WR timing and the airbox cover removed. Altitude is 500’-1000’?

Thanks in advance,

Mike H.

St. Louis MO


Hey Mike. .

There's a wealth of comments about jetting you WR if you scan down further in the notes. Also go to and there is a specific section on jetting your bike. You'll find what you need there. Remember when you jetting, air-filter type, airbox lid on/off, WR or YZ timing and exhaust type all make a difference. . . .


'00 WR; YZ modified, DSP exhaust system & UNI air, Jetting by Clark, James & Bryan. . .

with wr timing and standard needle you could run about a 172 main with a powercore iv. I run a 170 at higher altitudes, and same exhaust.


See "Jetting EKP vs DVP"

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