Shaft between generator head and motor snaped. Can the shaft be replaced or must the intire generator head be replaced. What is the cost of a new generator head? Also the motor was not ideling smoothly, it would alwasy be reving up and down if there wasent much of a load on it and the lights I was powering would go bright and dim. I put a volt meter in the generator and found the voltage would vary between 115 and 105 volts. what would cause that?