If you still have the old original mechanical regulator, it probably just needs to be adjusted to increase it's max output a little .....
Check both gaps first. On my '78, they were off and just re-setting them correctly raised the output. I didn't even need to mess with the adjustment screw. But eventually I replaced this antique with an automotive VR115. It works much better, much more consistent output. Once I installed a voltmeter, I noticed the output on the original was all over the place, often dropping off at higher RPMs when it should have been giving max output. All I can figure is the vibrations mess with the points inside it.
Check both gaps first. On my '78, they were off and just re-setting them correctly raised the output. I didn't even need to mess with the adjustment screw. But eventually I replaced this antique with an automotive VR115. It works much better, much more consistent output. Once I installed a voltmeter, I noticed the output on the original was all over the place, often dropping off at higher RPMs when it should have been giving max output. All I can figure is the vibrations mess with the points inside it.