Help yz90 yz250

[90yz250]

ive got a 90 yz 250 and ive got a problem with either the jetting or the crank seals but not able to decide so here goes got the bike it was toast new jug went 50 over to clean it up new head new boysen reeds fmf pipe pro circut silencer at 32:1 fouls plug every 45 mins 50:1 plug a day 70: 1 4 days riding still get lots of smoke and tries to foul out plug is black and oily plug is a br7es supposed to be a br9es drained trans oil still had 3/4 qtr in it any suggestions would be great if not im gonna shoot it oh ya it came with a 390 main jet and i droped it to a 360 which is stock top end in fifth gear doesnt pull any harder from 1/2 throttle to full throttle and it sputers at about 1/4 throttle to 1/2 throttle

[Flattrack]

Just a Quick Question

1) IS it useing Oil...

And I also would check the head gasket to make sure its sealed and not blown ...

[90yz250]

no its not useing oil from the trans and the gaskets are new and its got good compression no leaks from the head

[Kane]

Was there fuel in the tank that you might have added to? If so, have you ridden it enough to use up a full tank? Have you cleaned or replaced the air filter? Have you checked the pilot jet size? The needle position? The reeds, while new, may not be closing properly. The seal can be changed in a half-hour. Check your radiator fluid level too. Likely something easily fixed, just a pain in the ass to locate.

[90yz250]

hew fuel its got about 40 hrs of ride time air filter is clean pilot may be to small dont know yet needle position is 2nd slot from top radiator is full your right a pain in the ass changed crank seal tonight and still has the same problem so its got to be the jetting