YZ 250... HELP!

Ok hey guys, I picked up a 97' YZ 250 an it's in pretty good shape. The only thing is it runs bloody rich! It won't idle.. Well it will with the idle screw turned all the way in but barely. Went through the carb and it had a 48 pilot and 180 main. Seemed pretty big on the main so I went to 170 main and also tried a 42 pilot. Took it to a good friend who is my go to guy with this kind of stuff, he's been a mechanic at the local Honda shop for 20+ years. Really good mechanic. I took the carb to him last night and he went through it and it looked good. Also one of my other buddies thought it might of been the crank case seal (which I've read is pretty common to leak and can cause a rich setting) still nothin. I'm probably gonna take the whole bike to my friends and just have him go through it but what else could it be?? Thanks guys. Sorry for the long message

Do a pressure test! You just cant "look" at a crank seal and determine if its good.....


Also, make sure your floats are set.....

He put a new oem seal in it

He put a new oem seal in it

There is 2

Still, do a pressure test!!

Float level is good, how do you pressure test that? Just like a compression test?

Dude, you have an old motor.

The crank seals only last about 150 hours, then they must be replaced.

Float level is good, how do you pressure test that? Just like a compression test?


Not at all like a compression test, you need to do a leak down test. Google 'Leak down test two stroke'

Ok thanks guys for all the replies

Is this the stock carb? Keihin.. My buddy was thinking it came with a mikuni stockImageUploadedByThumper Talk1392097817.671902.jpg

ImageUploadedByThumper Talk1392097840.960639.jpg

Well that's good to know. I guess I need to figure out what mm it is and get the proper jetting. Or buy the stock carb and get it over with

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