lol i did this with my phone, very hard to do with my ape fingers.
Basically, I started at the battery and followed the wires to the starter, to the relay, to the ammeter to the ignition switch and so on. its how i figured out my two little starter wires were backwards, i touched that SOL wire in the center and got lots of sparks. Realized it shouldnt be a constant hot. pulled the starter and sure enough, backwards.