Gotta start with the basics first... Take the motor out and make sure the clutch spins free. The only way the motor can transfer any sort of power to the buggy and make it move is through that clutch. Something is fubar with the clutch. I was help a guy with his LST at the track which was doing the same thing. His bearings were seized and stuck to the crankshaft causing the clutchbell to spin. So you've either got bad bearings or the thing is shimmed wrong and the crankshaft bolt is pinching down on the bearing not allowing it to spin free.