ORIGINAL: N1EDM

I'm presuming that you've already checked the usual stuff, i.e., the fuel is fresh, there are no problems with the fuel lines (you didn't accidentally put a tiny 1/2A fuel line to the carb?) and that the carb itself is OK, HSN about 2-1/2 to 3 turns out. You said that bought the engine used. Has the engine been apart? If the engine is otherwise in good shape, and the fuel system is OK, the piston sleeve might have been installed backwards.

Back to the piston sleeve, I think that the exhaust ports are usually higher than the intake ports.

Bob