So I swapped to a new CDI, with a new wire and plug boot I put on it and hooked it all up, using the black from the engine, and I managed to get it running after a few minutes of trying.
The problem is I had to hold the throttle open to keep it running. I set the idle screw to keep it going and put it up on the chainstay stand, and as soon as I let the clutch lever out it stalled with no load against it except the wheel. I also noticed that I can walk it with the clutch lever released and turn the motor with the plug in today, which is unusual. Without my weight on it that doesn't normally happen.
So, now I'm wondering about compression loss. There's no mess (that I can see) around the head gasket so it's unlikely to be the problem. The next most probable culprit would have to be the rings, wouldn't it?