i've been haveing trouble with the jetting on my KDX220, it has the RB carb mod, it had a 1/4 to 1/2 throttle bog and it didn't rev out very good, i just put in a 40 pilot, AEN needle in the 2nd clip, 145 main and i put back on the stock silencer, had an fmf on, and damn did this wake the bike up, it's like a new bike, i'm pulling third gear wheelies no problem and it revs out awesome, just thought i'd share, i was getting pretty fustrated with the jetting but now it seems like i've got it ;)