1982 KZ1300 - Acts Like Direct Short When Battery Connected

1982 KZ1300. Cleaned out the carbs, changed the oil/filter, topped up the coolant, filled the float bowls today. Hooked up a car battery (original battery long gone) hoping to get it to fire.

Attached the car battery using jumper cables directly to the bike's battery cables, checking the polarity several times. Lots of sparks, like a direct short, when I connected the ground cable momentarily, but no sparks/smoke/smell from the bike.

The security/hazard/seat latch switch is completely disconnected, as are all the wires from the headstock/gauge cluster to the original full fairing, which is dismounted.

Fireworks with or without the key in the On position. Also found a four-conductor male-female plug set disconnected under the Cluster--fireworks both with and without this connected.

I haven't done my Full Diligence yet, but I was hoping this was something obvious to you gurus.

Thoughts?

grd wires can be black with yellow stripe ( at least on the 79's as well as black only) sounds to me like you've got a grd mixed up with a positive wire somewhere.

Glad to see you stopped before completely messing things up.
You need to find this short before going further. You can do this safely with an Ohm meter since the Ohm meter uses a 9 V battery at milliamps.

A few of checks for you to do to eliminate some of the circuits.
First- Hook up your Ohm meter between the 2 battery leads and note a resistance of "1". Then one at a time, remove the fuses and see if the resistance drops to "0". If it does, then you've found the circuit which is drawing the current and then you can focus on that circuit.

If pulling the fuses doesn't reveal the source of your short, then disconnect the pigtail for the alternator regulator rectifier and see if the Ohm meter drops to zero.
You stated major fireworks. That could also be a short in the starter but only if the starter relay got fried closed and is stuck closed so you could also disconnect the red lead going to the starter.

These 3 tests should point you in the right direction.
My big assumption here is this is a new bike to you that came as a "basket case" and you're working through getting it running???

Another thought - You haven't mentioned whether your starter motor spins freely or whether it spins when you try "jumping". None the less - You may have the "+" that goes from the battery to the starter solenoid, on the wrong side of the solenoid. This would account for the "sparks" due to the high current draw from the starter motor.

Yeah, I'm old enough to know when to walk away, especially as the sun was going down!

This is not a "basket case" in the sense of having come as a basket of parts that I had to assemble. It's a 5600-mile original that I got fully assembled, but I'm at least the third owner. The bike has been sitting outside for over 12 years, apparently mostly uncovered, but in a semi-arid climate more-or-less in the shade. The carbs were remarkably clean, but show signs of having been worked on before (scars on the heads of the main/needle jets).

The bike is known to have been dumped at very low speed (I'm betting on gravel) after which the owner's wife forbade him from riding it! The damage to the original Kawasaki-by-Vetter tupperware, and a couple of minor scrapes that didn't need to be repaired are what tell me that "fell over" would be a better description than "crashed."

The amount of sparks made me think that if the short was in a fused circuit, the fuse would have blown immediately.

This suggestion came from the "Kawasaki Z1300" Facebook page:

"(Mike Reed) Narrow the search. Connect battery to starter + lug and battery - to frame and see if it cranks over. On these old 2 communicator starters it is not uncommon for them to hang between and short. Turn the starter by hand some then re-energize."

That was news to me, but it would explain a high-current short very neatly.

Another excellent suggestion, Scotch!