Problems with the throttle electrical harness

So I recently bought a '78 KZ650 from some jerk on Craigslist who said it "runs great" and "has no electrical issues". Well, turns out after about 60 miles riding, it's has problems.

Turning on the headlights basically kills power to the ignition. On top of that the headlight was really dim, the front blinkers are barely perceptible when they are blinking. Rear blinkers were not functioning at all. This isn't a problem with the battery because it held its charge.. It seems like there is a short somewhere in the electrical. I should also note, the kill switch has been completely deactivated. The two wires have been pulled clear and are taped off in the handlebar.

We think the problem has been isolated into the front wiring harness, possibly in the right throttle handle bar. Before taking it apart does anyone have any idea what wire or switch could be causing this? Is this a normal problem on the old Kawasakis?

Does anybody have any experience with this in general?

Sure sorry to hear about that. It sounds like there is a lot of resistance in the circuit. I would suggest starting by giving all the electrical contacts in both sides of the handlebars a good cleaning. Might see if you can undo any electrical changes the po did. That's all I have. Some jokers shouldn't be aloud around electrical.

A multimeter would be useful, and since they're so cheap definitely worth the investment. Turning on your headlight drops power to the ignition - that means either +12V power is restricted, you grounding is restricted, or your battery/alternator can't provide enough power. But we can rule out you battery alternator if your battery keeps charge.

Since it's a range of issues, I'd put my bets on your connections - as unisher11b stated, try disconnecting all your terminals and giving them a clean. Keep in mind that engine oil isn't conductive - clean all oil of your terminals with WD40 or something similar, that will get rid of moisture and oil.

Also check all your grounding wires. It varies from model to model, but all will have a big grounding wire from the battery to the body, and many small ones for each different component going to the body. On my KZ the grounding wire is black with a yellow stripe.

+1

Bad grounds and corroded connectors are common on old motorcycles. Special repairs only complicate matters. Instead of WD40, I recommend Deoxit. It is made especially for the task and works fabulously. It can be bought at Radio Shack, electrical supply stores and online. It is more expensive, but I have had much better luck with it. Some small brass brushes are really helpful for the especially cruddy connectors.
A multimeter and a factory service manual (it will have a detailed wiring diagram and other essential information) should also be on your list of acquisitions.

P. S. Search this site for posts by MFolks. He has some really helpful tutorials on electrical system diagnosis.

Deoxit wotks great, but don't waste your money buying it at Radio Shack, I learned the hard way, I didn't even clean 1/2 of my connections before I ran out, so I checked the internet & was able to buy a can with 10 times more, for the same price as R.Shack, If you don't want to wait , you can go to a Home Depot & buy a can of contact cleaner to clean up all your terminals, another wire to check is your ground wire from the battery to where it connects to your engine or frame, on these old bikes many times you'll get rust & or corrosion, or loose bolt holding it where it's attached & you wont have a proper ground
Pete

I'd carefully open up the left and right handlebar "Switch pods", as they have factory soldering connections that may be failing. If you find ones in bad shape, I've got a repair procedure, just ask...