Oil in the cylinder

[mtc900]

I disassembled the cylinder of my 150cc GY6 last year to replace a number of leaking gaskets. The engine ran well but leaked too much. During teardown I noticed the piston was scorched on top so I replaced it and the rings. After a good cleaning everything was put back together with a new gasket set and it fired right up. However, after a few minutes running it started to smoke. No idea what color the smoke was as this was a few months ago.

So I just now got around to tearing it back down to find the cause. When I removed the cylinder head there was a small pool of oil above the piston and the gasket was wet with oil all the way around even though it wasn't leaking to the outside. Obviously the engine has been shifted around during removal so oil can travel up the timing chain cavity but I'm not sure how it would get into the cylinder.

I haven't pulled the cylinder off to remove the piston so the rings have not yet been checked. Rather I wanted to have an idea where to look before I went that far.

Has anyone seen this before? What should I look for as a possible cause?

Thanks!