yes, you should have the rotor checked for proper insulating values, any decent automotive electrical shop should be able to do this for very cheap if not free, (auto zone?) and have the commutator properly turned if it checks out. I have seen large generators cleaned with big orange and a pressure washer, just make sure you rinse it very well and dry it out completely. (The fella didn't dry one of them out thoroughly and it went up in smoke, the others worked fine though)
