This engine has a tapered sleeve. The top of the sleeve is a tighter fit on the piston than the bottom. The correct running clearance is realised at operating temperature. This engine should NOT be turned over cold when new. For the first few runs carefully heat the head with a blow torch or heat gun until the engine turns over freely. Then start it. Use a smaller than usual prop that will allow the engine to reach it's operating temperature and RPM but with a slightly rich (NOT SLOBBERING) needle setting. Run it for two or three runs with say an 8-10 oz tank, then it will be ready for use.

Ed S