Bergy, because it will start immediately if you prime it, your problem is most likely in the carburetor. Being an 80202, your engine has a PulsaJet carburetor, which has a built-in fuel pump. The pump uses a rubber-like diaphragm, mounted behind a plate on the side of the carburetor in your horizontal crankshaft version of the PulsaJet. It is not unusual for the diaphragm to deteriorate eventually, and yours has been in service since 1976, which is a long time for a rubber-like substance exposed continuously to petrol.
Part of the diaphragm is a pair of flap valves which act as the fuel pump intake and output valves. Sometimes they curl up a bit after the first thirty or forty years, and when they do, the pump can become reluctant to prime. The pump is located above the fuel, so it has to suck fuel to prime itself.
I suggest that you consider cleaning the interior of the carburetor, inspecting it, and replacing the diaphragm. You could also clean the fuel intake screen, which tends to become clogged with grass over time.
