It's been a long time since I have worked on a generator system but it seems that the generator may need to be polerized.
Get a jumper wire and connect it to the battery and then touch it to the A (amature) for about a second. Then see if it charges. I can't remember if this needs to be done with the bike running or not. I would try it first with the bike off and if that doesn't work try it with the bike running.
__________________ What do I know, I ride a Shovel