If you will post the full model and serial number. I can tell you when it was built and get you the information you need.
Onan parts prices for the older Onan units are very very expensive. I think they are doing it. To force people to buy new units. I priced a start solenoid today. 193.25 I found an after market one for 11.00.
StudeBaker never built Onan engines. They did own Onan for awhile. But Onan built most of the older engines.
Onan tech since 1980.