I agree. A snowmobile engine would be a nice way to go, but as Bighead said, buy the whole sled. I picked up 2 in the last year, both here in St. Louis (not known for snowmobile riding). I paid $100 for a Polaris 340cc and $200 for a Kawasaki 440cc. If you get the whole sled, you get everything you need including clutches and motor mounts.