Jim,
Did you polarize the voltage regulator? If not, when you turn off the ignition, current flows back to the generator (it becomes a motor). This might be the problem.
Anytime you remove the battery or disconnect any part of the charging circuit, it is a good idea to polarize the system by briefly placing a jumper wire between the "Batt" terminal and the "Gen" terminal on the voltage regulator - a spark will fly.
Tim
