Try running a ground wire from the base of the regulator to the generator housing. Sometimes the firewall sheet metal where the regulator mounts doesn't provide a good enough ground for the relatively low current it takes to operate the field circuit. Just a couple of ohms of resistance between the regulator housing and the generator field frame can mess up the regulator operation and result in a "no charge" situation.
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!