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
My advice would be to not buy a rotax kart that old. first the chassis even if in good shape will just not be terribly competitve in a tag class. you will need to upgrade the bumper for about $180. the engine is a huge can of worms. you will need a rebuild. The cylinder head that you see outside is merely a cover for the water jacket and will run around $80 for a new one. Typically the crack is in the cylinder so my bet is it is likely cracked also. Then to race it will need to be upgraded based on the age of the kart here is what I would assume would need upgrading to race
cylinder $675 (or more)
clutch and balance gear set $475
evo upgrade kit $1400
the engine rebuild will cost:
$500 labor (at least)
$150 for the complete piston kit
$375 for the rod kit
$75 for the seal and gasket kit
$100 for bearings
you can buy a decent rotax that is current for about $2000
look to buy a chassis that is no more than 4 years old. Older is ok if it is in good shape and there is no intention of racing it. If you want something cheap to get started in racing get a Briggs LO206 kart. with those you can buy an older chassis that is in good condition and be competitive but expect to put a bumper on the back and go through the brake system.