An excellent sealant for this purpose (no gasket, metal to metal, narrow clearance) made by Permatex is the 51813 Anaerobic Gasket Maker. 51813 is an anaerobic sealant, which means it only cures in the absence of air once the clamshell or cylinder is reassembled. Any squeeze out stays liquid and can simply be wiped off on the outsize. Inside the crankcase, the fuel mix washes it out with no ill effects. This is the same stuff used to seal up crankcase halves on 2 stroke outboards, from the little single cylinder ones to the big V6's. Good stuff, and easy to work with. Loctite 518 is similar, if not exactly the same.
When I resealed my Wild Thing last year (bad crankshaft seals), that is what I used. The tube says that once the parts are assembled, it's ready to go in one hour. Based on their cure time chart, 1 hour is about 50% strength. 10 hours is just about full strength, and is practically fully cured at 24 hours. I waited a day before trying to start the Wild Thing. Been running like a champ ever since.