How do you find a bad wire

Okay, so I origanally posted this question on the engine board, but then it got moved over to Carbs, now I'm thinking my problem is electrical.

Here is the Post

Here are the basics:
1980 KZ550c
The bike wil not idle (or run well) on all four cynders. When the bike is physically moved (on or off side stand, shaking it back and forth, kicking the tires... I kid you not) the other cynders pick up and it runs great for a couple of seconds and then dies back down. I think I have traced the problem down somewhere in the wiring harness. How the heck do I find my problem in there?!?! Am I just facing a lot of trial and error testing one line after another? Is there some kind of short cut that anyone here knows?

Have you changed your coils, or upgraded your ignition system lately?
Sounds like one of your coils may be cutting in and out. The wires that power the coils run under your gastank... look for connections there that may be loose or corroded.

start checking for loose plugins,corrosion;)