If your engine does not run at top speed the clutch will not open all the way. The Harley engine always turns faster in reverse but that is entirely another subject and has many theories. Any hoo if your cart will run around 18MPH + or - a mile or so you are in good shape. If not I would suspect engine condition or tune. I expect your governor has been disconnected. I do not know much about HD carts newer than 1980 but a lot of things are the same!