Alright, in the interests of spreading good info here, it was the fuckin' tank ground. Had nothing to do with the lights, somehow, unless having a bit more load was just too much for an already crap ground. I replaced the ground with a larger gauge wire, ground away some of the crap at the contact points with sandpaper, started right up. However, things I learned:
The board will happily turn on at 8.5 or 8.7 volts; I'm reasonably sure that the actual acceptable voltage is just <12v.
You can replace that bullshit diode at Mouser
, they're like $.35 a pop. If you're screwing around with the ignition, this can either be soldered in at the normal spot, or at the back of the bike, going into the pink wire. The board doesn't care which.
If you want or need to re-key a 919, the best way is to order the base contact portion of the ignition from Partzilla, here
. This will get you the correct, US ignition base, with the right wire setup and the diode already in place. This can be mated easily to any of the 919 keysets from China, available off eBay or wherever. This is not hard to do, but is pretty annoying. I'ma make a post on just that bit, I think.
You can also make an Asian-market 919 ignition work by splicing in a diode. If you open up the butt of your ignition and don't see a pink wire at all, you have an Asian-market ignition. If the diode fails, or just isn't there, the bike will throw a FI light and refuse to prime the pump. You won't get any blinking error codes or anything.
Taking apart the entire ignition is something I would now recommend at like 20k. Mine was filthy at 40k, bad enough that it was grinding internal parts. Note that there are a few springs that you will want to keep track of, and note that the plates in the actual cylinder can and will fall out. Make sure that, if that happens, you test to make sure you have them back in the right order. This is what lets your own key turn the cylinder.
Last but not least, do not in a million years trust the insulation color of a wire to tell you what it does. Test with your multimeter, or at least one of those 12v circuit testers. The switch for the HF lights I got was wired as white-hot, black-ground, and blue-neutral return, which would have at a minimum blown a fuse if I hadn't checked.