Hi Charlie. On a Generac 4 hours of run is not enough to burn out your brushes and its more likely that one of the oil sensors (temp and pressure) are bad and making the CCG board shut the engine down. Dead give away is that it worked fine and then suddenly would'nt stay running. The first version switches were too sensitive and were prone to failure. Make sure you get the newer version. I replaced my pressure switch already and am in process of doing the temp switch now. They are located above the Oil Filter adapter housing but under the sheet metal. I suggest you learn from my mistake and replace both while you've got it down. If I knew where the CCG board is located I could test to see which one is actually bad. Does anyone know the location of the CCG Board? If you don't have the Generac, I don't have a clue. If you don't have the manual for the Generac tell me and I'll send you the PDF.