Grand Prix 500
Main Motorcycle: 1973 TR7
Join Date: Jul 2012
Location: Hickory Creek, TX
10 volts isn't near enough. you Headlight draws considerably more than stock, but it shouldn't be that high of a draw. Check the output at 3000 with the lamp off and see what you get. Be willing to bet it still won't be above 12v.
You need to determine if the zenner has bit it, teh stator, or the regulator. Meter your 2 stator leads for A/C voltage where they plug into the harness. Should see upwards of around 9 volts A/C when running loaded at around 2500-3000RPM on each leg (white/green and green yellow wires if memory serves). If one is low, swap the leads where they plug into the harness and test again. If the low leg still reads low plugged into the different connector you either have a problem with the connection or the stator itself. If the voltage drops on the previously normal stator leg, then you have a problem with the harness or rectifier.
If you check solid on both leads, then you need to check the output going to the zener, after the rectifier before the zener. You will be checking D/C voltage at this point. If the zener is bad and shedding to ground too soon, you will read low period. In essence, you need to disconnect the output from the rectifier to the zener and check raw output through your meter to ground. There are several ways to get it done, but not sure I can acurately describe how to do so, and do not want to risk spiking your Boyer Box (bad news if ti happens). Maybe someone else can step in and describe this step. If not, I will make the attempt, but will reccomend extreme caution doing so to ensure unregulated voltage doesn't reach the Boyer.
A GOOD friend will bail you out of jail, a TRUE friend is sitting on the bench next to you saying "Damn, that was fun!".