Alsport Tri-Sport RTS. From the bumper, battery mount and lights it may have been a street legal but maybe not. Probably had electric start. Maybe a 4 stroke, as the engine mount looks different then the 2 stroke mounts I have seen.
Edit: the frame is different then I know. Double tube but SOO much is missing,(engine, exhaust, TQ drive, jackshaft, entire rear braking system).