Have you checked the voltage output at the armature terminal with the field wire grounded? It's possible the generator is working right and the regulator isn't allowing the charging current to get to the battery. There's a pretty simple procedure to test that possibility, but it's not a subject to tackle with a keyboard.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!