Since it is a Funyun-ized bike, I would check the battery cables, he sure knew how to "rig" stuff up. Maybe it is as simple as that
When I first got my quad the seller didn't know why it wouldn't start. Got it home put the battery on the charger and once it was charged it took a few times then it started up, then the smoky exhaust came out for a bit then it was fine. After that we did an oil change, new gas and spark plug.
Sometimes it just the little things that are needed to get it going.