I am certain Joe knows more about engines than I do, so I won't really try
to answer your question; but...
I know two people with problems similar to yours. They drained their gas
and put the generators away. The next time they went to use them, they were
For anyone else reading this:
1) Put gas stablizer in and start your generator monthly, or
2) drain everything and put oil in the cylinder.
One of them was a mechanical engineer who certainly knew better.