Phil,
Before you give up, Make sure that you know how to get the unit out of where ever it is.
Next, get on the web or the phone and find a local friendly small engine shop. When you talk to him, have the model numbers and all the information at your side. If you find one that will even look at it, you are half way there.
Onan engines of all manner power small machines all over the industrial world. The generator is just an engine attached to an electric machine and it doesn't sound like that machine has any issues.
Good Luck
Matt
