Hard to imagine it being anything else,with a one-piece cylinder. Maybe the rings transitioning because they're new (?). If it's the piston, you'll be able to see an extra hole through the plug hole. That would be the first one I know of.
I'm still putting my money on the plug (Old and stubborn..). lol Mine got real easy to turn over the other day. It was the plug. The engine was new, and I hadn't run it much. New plug, and it started, and tuned up for me.
~ Jim ~
