I own a 1978 yamaha XT500 bought it for 200 dollars cash, it runs real strong in the bottom end, but seams to top out real quick in each gear. the carb that was on it when i got it was a 38.but that carb was seized up from siting with gas in it for at least 8 years. so i put a 36 on it,becuse i had it on the self from a 2stroke bike i had. my question is what is the best carb for this bike? it has white bros pipe and cam setup. thank you bryan smith.