I have a '04 KFX 400 with full Pro Circuit exhaust, jetted, no air lid. Runs hard in 1st and 2nd and beginning of 3rd. Once your halfway thru 3rd and into 4th gears, you can feel the power level off, then pick up again a little in 4th. Is this possibly due to needing jet work redone or would a CDI upgrade take care of this??

 

id try and borrow sombodies cdi and see if that fixs ur problem.