I know this is going to sound crazy. I bought a 98 KX 250 about a month ago, haven't got much time to ride it, only a few times. But when I go out my long driveway and get on it hard, right when the powerband hits and the back tire starts to spin, it will downshift. I've never had a bike do this ever before. As a side note, I've been riding bikes for years, i'm not accidently hitting it with my foot, or pulling in the clutch. At first the chain was really loose, and i've tightened the chain(actually had to take a link out of it) and now it isn't as bad but still does it. If I ride it like an average rider, it won't do it, its only when I push it hard that it will downshift once the tire starts to spin... Any ideas would be great. I've googled and searched everywhere, and haven't had much luck.