1) dirty carb
2) dirty carb for real
3) no really fuel is not getting into your engine, clean it
4) you cleaned your carb? like the emulstion tube and jet?
5) no really, the fuel system includes carb, fuel line, and tank. all of those were really cleaned out?
6) no seriously its the carb
Just kidding, its not the carb? But if it were, you would need to really clean it.
1) how about the drive unit, is it dirty? will the splined hub freely slide through the moveable sheave?
2) how about that drive and driven unit, are the non-moveable sheaves lined up perfectly?
3) you sure about that carb being clean?
4) you sure you put the drive unit together correctly and the springs and weight pack are lookin good? you know that you can accidentally install the weight pack backwards?
5) you sure about the throttle going to max? move it(<-- the actual throttle butterfly that the governor rod links to) by hand when your on the bike. no difference?
well crap, ummmmm........ cant help ya there..... you sure about the belt? Im assuming its a new unit with the backplate and the belt was the right belt that came in the kit? you didnt go install it backwards too did ya?
maybe gearing? are you like geared for it to go 50 mph and it just doesnt have the umph to get you there?
6:1 gearing and tires no larger than 18-19" outta get you to 35-36 mph, any gearing higher(e.g. below a 6:1 ratio) than that is going to put you up to slow starts and mediocre acceleration.
still cant fix the problem?
yeah you really didnt clean your carb did you? Whelp what do i know anyway, im just spaz typing. Good luck!