put on my CRF250R. does what it says it does. i can run a higher gear and it still pulls strongly.doesnt affect top end at all from what i can tell. it is a pain to install because you have to take the carb. out.when i got it though it looked like it had some rust on it. i dont know how because i thought it was aluminum. maybe it was something in the finish. after i scrubbed on it with some steelwhool, i put it in. either way i have about 8 hours on it and the engine hasnt locked up so i guess we re good.