[Voltage regulators for generators are adjustable >I have never had the cover of one for and alternator My 1922 Model T speedster has a 3 brush generator and a cut out relay. It is adjustable by moving the 3 rd brush location in the generator. another option might be changin your pullies. In the 50's A high reving engine could explode the generator windings.
Is there such? I want to have my m/c battery charge a little higher, so that it powers the MSD box properly.
From MSD "The Ignition will deliver full voltage with a supply of 9 - 18 volts."
Anyway, depending on your regulator if its ground is through a wire and not from being bolted on, you can add a low ohm resistor in the ground line. It would be hit and miss but I'd start at about 3.3 ohms, 1/2 watt or maybe 1 watt would be enough. The higher the resistance, the higher the output voltage. That is the ground wire from the actual regulator to ground. Not the alternator ground.