[Topspinmo]

OP did not give enough information to diagnose the problem other than guessing. For it to be belt it has to be slipping which usually creates squealing sound unless contaminated with oil creating unusual high rpm when cart seems to be not up to speed. Going up the bridge if belt was slipping the there would be squeal (unusual noise) and rpm’s would be why high or on the max governed setting. Belts can be visually inspected and measured. It should be obvious if belt slipping signed heat and belt deterioration therefore needs replaced.

The spark arrestor for one blocks exhaust gases from escaping even when new anything restricting exhaust means air coming in has harder time going out. So if cart seems to be sluggish and engine rpm struggles to get to governed speed first thing to check spark arrestor. Some try to clean it, just going to restrict again eventually, some option replace it when cost couple hundred dollars with same problem returning in 3 to 5 years. And yes it will restrict exhaust again causing same problem. Some elect to remove restrictions by punching or drilling out screen therefore eliminating problem for carts life. So there the options if it actually is the belt or the spark arrestor. Most likely it’t the spark arrestor blocking exhaust gasses lugging the engine down.