What else can I check.

[Southy]

I just bought a 87 250r. It keeps fouling plugs. It runs great when its wide open, but when you come to a corner it starts to foul out the plug. As soon as you get back on it hard it cleans itself out. Well atleast most of the time it does. I've got a 38 slow jetin it now and it still does it. Is there anything else I can check.

[shamisc]

Try dropping the needle by raising the clip up one notch. You may still need to go down on the jet size. Sounds like its pretty rich to me, but I'm not that familiar with that carb. It could have trash in it and just need a good cleaning. Was it running fine before and just starting running rich?

[Southy]

When I bought it the guy told me he ran it really rich because he would rather foul a plug than replace a piston. He had it running pretty good wide open but very rich on the low end. I changed it to a 155 main jet and went from a 42 to a 38 slow jet and put the clip back in the middle. Part of my problem is I'm used to riding a four stroke, but today when I was riding it was doing it no matter how hard I rode. When I pulled the plug it was a medium brown color and very wet.

[Pele05]

I was taught by a mechanic that the easiest way to see if your to rich is to go to the biggest main jet and rev it out , if it bogs it is too rich, step it down a size till it doesn't bog. That way you don't have to worry about running too lean and burning a piston. Pilot jet only effects idle to just above idle. Moving the needle will affect off idle to about 3/4 throttle. Size of main will mostly affect 3/4 to full throttle. How's your oil mixture, how is your reed valves? Make sure you have good compression.