Thank you everyone for helping me. Finally got a few minutes to address this.
The previous owner had put an aux fuse box on the bike. It was so well done that I did not realize the MAIN stock + wire was not connected, but was in fact shoved behind the battery by my clever helper. I saw the aux wire and mistakenly thought it was the main stock wire.
Full disclosure: my friend Steve found the problem.
I think I'll take the whole bike apart soon so I know what goes where when future things crop up.