ok i have a 2008 CRF250 and ive raced most of my life. since you have checked your wheel bearings and spokes and havn't found a problem then i suggest you check your suspention. believe it or not your suspention has a lot to do with the way your bike handles in corners. when you come into a corner, you hit your breaks which compresses your suspention and then your back on the gas and off the break and the suspention comes back up. So it may be to stiff or possible too soft. the only other suggestion i can give you is you may need to work on your form in corners, maybey your not low enough..and remember to keep your elbows up....i hope this solves your problem, thanx