Hi Bolens, there are two basic types of generator, they both involve spinning a copper winding inside of another set of windings. In one type, the electricity generated is taken from the rotating windings, in the other type the electricity is taken from the stationary windings. Without a lot more information and photographs it is very difficult to determine which type you have and to offer any advice as to how to to flash the generator. Could you also please provide some information on how the voltage is regulated, I would expect that it probably has an old selenium rectifier and wire wound rheostats.
More info please.
Bob