What’s your intensions for this engine/chassis package? A cracked head would be the tip of the iceberg. The engine will require a full rebuild because you have no idea how much wear there is to the crank, rod, piston, ring and cylinder. The carb will need to be cleaned in a sonic bath and rebuilt. Seals for the water pump will be bad. A Rotax is not the cheapest engine to repair and we haven’t begun speaking about making this engine legal to compete. If you’re going to race with it, check with the association you plan to compete with. The clutch will have to be upgraded. An upgrade to the latest spec EVO will be costly and will require replacing the top end of the motor, plus the electronics, plus the carb. Can you see the picture here? Call any Rotax repair center for an idea of the cost. Engine wise, I’d suggest a simpler engine to start out with, a Yamaha Kt100.
Have no knowledge about an Avanti chassis. Check for the availability of parts and that chassis is not bent or cracked.
LAD Specialties customer / tony kart / rotax / kt100