WELCOME to AAC!
I am TOTALLY UNABLE TO READ MINDS, and so it will help quite a bit if you tell us what your Honda 3000em actually is, and a few more details about the problem. Otherwise, folks may just provide random guesses, that may not be at all useful.
I presume this is the generator? Theres a owners manual PDF avalable on google with a circuit diagram. It shows an AVR for voltage control. Its most probably faulty.