Pretty sure that is a generator engine. I've never heard of one going bad so I can't tell you about rebuilding it, but gump and Marboro Man have them and have had several of them. One of them may be able to help you.
I wasn't really comfortable til I was following Pauly. I'm not good at riding with new people and I have followed him before and know what he's gonna do and that he won't get me into trouble. Major reason I don't do group rides that I didn't put together. Which has been years.