i have just got a 2003 kfx 400 and have a few questions. first i have a full yoshi r-3 exhaust and was told to put a 155 main jet in it, with 2-1/2 turns out on screw. sea level is 600 ft. alsoi was told that the 2005 models have new design cams and a 37 carb. the parts sites all show the same part#s for a 2003-2007 ltz-kfx and dvx. any help will be great. thanks.

 

i'm not quite sure where the question is at!! lol..
since you have a freer flowing exhaust, it will permit you to load more fuel into the motor...thus the 155. cam timing wont affect that tho within reason.. the cams in quads and bikes are VERY radical to get the power they get out of such a small displacement.

now, that screw that gets turned out 2.5 turns will be the enrichment screw!! not the actual jet.. the jet has to be seated tight...
i figure you know that, but i err on the safe side with desribing carb related stuff. they can be very tricky to work on and understand if you're not too familiar with em.

i dunno. if i didn't answer anything, (which i probably didn't) then just post up with something specific for my feeble mind to grasp!!

good luck and have fun!