Originally Posted by tedsander

You have a leak and/or shot compression. See if sealing helps. Make sure all screws are tight, especially the head. "ABC" engines have no ring, and depend on critical clearances when at running temp to give correct compression. Turned over slowly they may feel like they only have a little, spun faster and they feel better. Are best after they have been started and are up to temp. BUT, also easy to run too hot, or a myriad of other issues, that scores the piston/liner, in which case they never will have enough compression.

Hopefully the gasket will resolve the issue, then you can have a more dependable needle setting to resolve the too rich/flooding issue. And running leaner may help with the plug issue - may be a bad plug, or it may be just too much fuel putting the fire out. But the needle won't adjust right until any possible leaks/compression issues are resolved.