Polaris sportsman
#1
#2
Part of the problem could be carb related. If you tear a carb apart don't just clean old parts especially a needle and seat.You can get a good kit for the price of an oem needle and seat.POLARIS SPORTSMAN 335 CARBURETOR CARB REPAIR REBUILD KIT 1999 2000 NEW SEALED | eBay On the belt was it an oem 3211077? If not could be part of the problem on speed or could be belt fragments or belt dust in the clutches need to be blown out or the rear clutch buttons could be worn down. Item #17 in the parts break down. One other thing I'd do is pull the black wire from the reverse limiter module.
#4
Any pieces of belt or dust can affect drive or driven clutch operation. Blow out the dust in an open area as it will be a lot. Open the rear clutch and use an air nozzle in the cracks. Wear a dust mask or hold your breath... If that doesn't solve the problem remember the other things I mentioned.