Great manual, tried backtracking site to select my generator but couldn't do it.
Onan Marquis 5500 BGM.
I have the installation and owners manuals but they don't have the details like your parts and repair manual.
Specifically looking for info on carb, didn't use for 5 months so most likely gummed up carb.
Like most carbs it does have fuel bowl but where the bolt holding it on would be they installed a lever for altitude. It would be a good starting place to clean, without having to take the genset out, very little exposed parts where it sits.