So this is how it should work.
Here's the black with a little jumper on it to make things easier.
The plan was to use an Ohm meter in "buzz box" mode.
Case to blackwire should be continuous until the points open.
Some adjusting and checking.
Looking about right, this is open.
Check the gap.
Here's the function check. The buzz board didn't really work because the light in the description just dims and doesn't go out. So we put it to just impedance read out, but we weren't convinced it was correct.
So we pulled the rotor back off and disconnected the generator stator wire at the breaker.
We taped the wire so it would connect again, and reinstalled the rotor.
This test was better. We used a battery charger to case and to the testlight at the points breaker.
So after this we pulled the rotor, attached the stator wire to the breaker, reinstalled the rotor, and properly torqued the rotor nut. Hopefully it will make a spark at the correct time when the coil and sparkplug get connected.