I have a 2003 cr250r that bogs down in the low rpm range when riding. I tried everything up to this point that I can think of. I have done the following: New air filter New top end New spark plugs New clutches New clutch basket R/C valve is adjusted as described by the manual. I don't know a thing about this r c valve. It opens and closes. Not sure how it is supposed to function, but seems to function correctly. Cleaned carb New carb jetting. I put the recommended jets for my altitude. I did notice the problem is better or worse when I adjust the air/fuel screws on the carb, but no matter how I adjust I can not rid my bike of the problem. Is there something in missing? The good news is that my bike is nearly completely restored. Bad news is the problem is getting costly. Any suggestions? I really want to ride this weekend.