Onan 4000 Microquiet KY no start - Oil level switch bypass

That is a pretty good trick. You could take a wrench and grind the outside edges very thin so you can get on that bottom nut. But first try the screw on the bottom to empty the bowl and then hit the prime switch to run gas out of that outlet and see if it might clean it out. And when your turning it over to start it tap lightly on thay gas soleniod and see if it helps.
Its called the float bowl drain valve in the op manual you may have a little water in the bottom of the carb so try to drain it.