How do you take a generator head off of a generator motor?

I have an old generator that the motor doesn't run. I want to salvage the generator head and make something like a wind, steam, or bio diesel generator I haven't made my mind up yet. But for now I need to dismantle the head from the motor. I think it has some kind of a ratio box on it too I'm not sure I've never done this before. I sure would appreciate any help!