[gaz]

I just went through all this with a kx250. Yes it started ok, ran 1st and 2nd ok as long as you didn't push to hard (like wot) into the power band otherwise it would run erratically and foul plugs and it seemed to be excessivly rich. I leaned of the main and pilot and tried two different needles and clip positions as the problem seemed to effect the mid range of the bike. It made no difference. From reading other posts I suspected the right hand side main bearing seal to be leaking. (this really makes a bike run rich, left hand side makes it run lean and both don't respond much to rejetting). The best way to determine this is to do a crank leakdown test as it doesn't cost much and confirms the leak. This can be done with the motor in the bike. I did thid after I checked verything else like reeds, float etc. Drove me crazy! If you google "kx250 crank seal leak test" you will see the test results on youtube.