I have 02 lt80 and have replaced the rollers in the front clutch or variator. and the belt. before you would have to rev it to barely move. now it will spin the tires and pull me up hills. but its top speed is about 5 mph. the part where the rollers ride looked a little worn but I dont know if this is the problem. I also baked the pipe out in my fire pit. and made sure there was no restrictor where the pipe bolts to the cyl. and made sure there was no spacer in the trottle in the carb. what am I missing??? the rear clutch ???

 

Have you cleaned the carb? Sounds like that could be the problem.
Let's go from there.