03 kx250 jetting help

Purchase a Service Manual for your bike. It'll come in handy for disassembling the powervalve as well as doing maintence like rebuilds. If I remember right Kawasaki offers a optional thicker head gasket that'll lower the compression a notch. That'll smooth out the power delivery and the hit. It's a very cheap fix. Another thing to try if you find the hit a little on the hard side is to try a flywheel weight. It'll slow done the pipey'ness of this motor and make riding the hit more controlable. You could also experiment with final gear ratios. Is the gearing stock? I usually go up two teeth on the rear sprocket to put the meat of the power a little lower in each gear. If the current gearing is not stock you could reverting back to stock to see if that helps. Or you could go a tooth or two smaller on the rear if the bike still hits too hard and too soon. Stock gearing is 13 Fr-49 Rr. A MotoTassanari V-Force is also good at smoothing the hit out. You could also try changing the expansion chamber on this bike. The stock one (my personal preference) hits the hardest and is one of pipey'est of the pipes I've tried. The Pro Circuit Works pipe is more of top-end pipe and eradicates the bottom-mid-range hit (may be just what your looking for?). The FMF SST smooths out the bottom-mid range hit and seems to move it upto the upper mid-range instead. The FMF Gnarly seemed very similar to stock and is very pipey. I hope some of this has helped. I found the jetting stock to be very close, I only needed to go from 168 main to a 165 to clean it up.

On the 03 kx 250,when the temperature starts to drop in the high 40's the needle is too lean.Go for the 3rd clip, and you can bet your pilot will richen up from the needle position,so adjust that also. I ported my motor and bought the squish down,stock compression,I am running AV GAS,but even on a stock motor with pump fuel your needle will still be too lean in the 40's. Stock reeds,Boyesen reeds,carbon tech reeds, it will still run lean.

Speaking of reeds,after a good few rides depending how you ride, the kx reeds will not hold up. The carbon tech reeds are outstanding, enough said!!!!!!