Make power or run? If it quits running when you release the start switch there is a simple fault somewhere. If it stays running but won’t produce power then there is a whole different set of faults. The easiest way to diagnose a problem with these is to find a technical manual, spend some time going over the procedures and terms. Then follow the diagnostics in the manual. I had no power production on mine, took me about a month of off and on reading, researching, read some more, tracing wires, and trouble shooting. In the end it was a corroded relay and the repair cost me about 30 minutes of wrenching time and zero dollars. I spent 10-12 hrs reading and researching. Since I did all the research and learning I know the machine better and I am more prepared to deal with issues. Taking some time to learn more about the machine is well worth the time! Components on these units are not cheap and you can be $500-1000 into a repair when in reality it could have been solved with no money or $20.

You have probably fixed this issue, but what you describe is the stator not providing the excitation voltage for the main generator.