When polarizing the generator as Stuart described, it is good practice to ground the generator field terminal as well. That way you don't risk damage to the current and voltage limiter contacts in the voltage regulator. The possiblity of regulator damage is small, but since it is unclear what is going on with your system, the extra step may save you trouble. Grounding the field terminal with the engine running should give you full generator output, limited only by the battery and the resistance of the armature windings- which isn't much. So don't leave it that way very long.

Harvester