1978 Indian Moped won't charge the battery.?

The battery is new, if I charge it using a battery tender it will hold a charge. But the bike will not charge the battery.

Checked to be sure the battery has a solid ground, and there is continuity from the negative terminal to the frame/engine. But the rectifier has no continuity from either terminal. I am assuming that would be my problem, but there are other readings that make me wonder if there is more to it.

Testing the voltage from the magneto to the ground, per service manual recommendations returns about 20v steady, when the acceptable range is supposed to be 2-6v according to the manual. This seems like low voltage to me, but I am not the expert.

This is where I am stuck. Help!