My bike was in similar condition when I bought it. Wiring was totally screwed. The grounds are shared by a bulk bullet connector, that's a good place to start. Find the connector that has 4 slots, this is your ground. from there your tail light has a parking light positive (check it with your headlight switch on) and a stop light (check with foot on brake and or hand brake lever) using a multimeter with black attached to ground...or you can use a test light with the alligator clip clipped to ground (fyi frame is ground so long as you put it on something NOT coated in paint...battery is better though. good luck its not as bad as it looks