I also have a 2003 KX250 and was running 32:1. I recently switched over to 40:1. I found that running 32:1 my bike would run perfectly, the next day it wouldn't run at all, and then the next day it would be running great. This is also probably due to my riding style. I'm not always on the pipe, I don't lug the bike around either though. Also noticed alot of spooge comin out of the tail pipe. After running 40:1 I haven't had any problems. No excess oil coming out of the silencer, and it doesn't smoke when warm. Just hope I'm not starving my engine of lubrication :ohmy: