I have a two person kart with a 6.0 hp Tecumseh powersport engine. The engine runs fine. When I start the motor and it sits for a mintue the kart wants to take off on with no one in it and the engine stalls. It makes a whining type noise. If i start the engine with the back wheels off the ground it runs fine, but the back wheels move. I think it is a clutch problem, but was wondering if it can be fixed or do I need to replace it. Thanks for your help.