Ok sorry Doug, I just re-read your initial post, so it is a sidepull, what threw me was you were pulling the flywheel off,why? I thought it was an early one with points ignition. You say spark is good and with new plug. My guess is that the float needle will be the culprit. Get a can of starter fluid and give it a quick squirt in the plug hole, put the plug back in and give it a pull and if it attempts to fire you can be 99% sure it is the carby problem. The other 1% then can be is crank seals leaking but that is not very common
