If the piston is traveling up and down when you turn the rear wheels, you do have some sort of clutch failure or the clutch is out of adjustment. Before you do anything, do you have the L&T tools to remove and service the clutch? The starting point with clutch slip should be around 6k and adjust towards a higher engagement RPM. Never start at 11K and turn to work your way downwards. All you’ll have that way is smoke. You should end up between 7.2 and 8.5k.
For the clutch not turning freely, if this is a new clutch, there is the possibility that the adjustment screws are way off. If not a new clutch, disassemble the clutch and carefully measure everything as specified in the manual. Have found that the dog bones do wear and break. If you have a kart shop in your area, ask if they would help.
As for the starter nut, check how far in the clutch goes on the crank shaft with and without the key in the shaft. Your key could be too large and not allowing the clutch to fit tightly on the shaft.
Also, L&T has a phone and fax numbers plus email. I’d give them a call.
LAD Specialties customer / tony kart / rotax / kt100