Yep, you were right on with that one, mates. I had used a decent amount of electrical tape to try and hold the cheap wire connections together better, but it just didn't stand up to the Arizona heat. The adhesive melted and one of the connections slipped out. It was contacting enough to give me spark as long as the rear wheel was still forcing the engine to turn. The fact that I ran the clutch cable, next to these wires probably didn't help.
I should have figured it was, a) something stupid, and b) something electrical.
I'm thinking of cutting the stock connections off, stripping the wires back a tad, and using nice automotive ones. Pretty easy modification and will probably hold up much, much better.