Golfoh,
Now you have some guesses, and that is all anybody can do from internet land...
So, put aside the time to run it and do a diagnostic. The first and simplest should be to pull a plug wire and put a screw driver in the cap and hold it near (1/8~1/4") something and crank.
Do you see/hear a spark??
Yes, then it is a fuel problem and probably the pump.
Put the wire back on and squirt some fuel into the carburetor.
Does it fire now? Fuel problem confirmed.
No, then you have an ignition problem.
There things are neolithic (new stone age) technology, so get out the Onan book and track it down.
Mine are both 45yo and have bouquo hours and the one in the coach will start and run as long as I keep it supplied with fuel. The other one does not have a battery because I stole it to start the snowblower.
Matt