81 kz750 ltd H2 harness short circuit problem

I recently picked up a new project.
81 KZ750 H2.

I rode it home about 30 miles from where i bought it.
Battery in the bike was dead, and to make things worse the positive lead of the battery was exposes and shorted out as it vibrated and touched the frame\battery basket.

I made it home and the first thing i went to do was put the charger on the battery.

As soon as i connected the the battery to some juice, a wire, black\yellow, that runs form the starter solenoid to the harness, and loops back to the other side of the bike (ground and negative terminal) literally flamed out.

After taking the harness apart i found the following:
1. the 20 Amp fuse was missing and the two wire leads shorter and bunched together to close the circuit.
2. The green wire going in to the signal selector switch (bottom left handle bar) was broken off and shorted out against the metal of control housing.
3. Only one of the turn signal switches works (not sure if it is the hazards or turn signal unit).
4. two wires running to the rectifier were burned - The white\red wire was damaged pretty badly and melted the wire down to the core fairly close to the rectifier, though left enough lead to solder on a new wire - the brown wire that runs in to the 6P plug was burned as well.

I took the harness apart and replaced the burned out lead wire with new similar gauge wire, good solders, and new isolation for all exposed locations.

After replacing the burned wires i put back the harness together on the bike, and installed the missing fuse - everything seemed to be working, and i even had starter - this was before i found all the other shorts - and after hitting the signal switch all fuses exploded.

I have taken the harness off again, and out it back, this time with new fuses and no shorts.

I have head light, i have signals, dash lights (on high beam only for some reason).
No starter, no neutral light - the neutral lead, wire and bulb are good, the bike is in neutral as well as no rear lights at all. Fuses are no longer popping.

I am at a loss and not sure where to proceed from here.

Any and all help is welcome.

Would this help?

kz.bike-night.com/media/KZ750-H2-US.jpg

I have the shop manual and i am following that chart as best i can.
I guess i am looking to see if there is anyone out there who has experience with this sort of thing.

"As soon as i connected the the battery to some juice, a wire, black\yellow, that runs form the starter solenoid to the harness, and loops back to the other side of the bike (ground and negative terminal) literally flamed out.

After taking the harness apart i found the following:
1. the 20 Amp fuse was missing and the two wire leads shorter and bunched together to close the circuit.
2. The green wire going in to the signal selector switch (bottom left handle bar) was broken off and shorted out against the metal of control housing.
3. Only one of the turn signal switches works (not sure if it is the hazards or turn signal unit).
4. two wires running to the rectifier were burned - The white\red wire was damaged pretty badly and melted the wire down to the core fairly close to the rectifier, though left enough lead to solder on a new wire - the brown wire that runs in to the 6P plug was burned as well."

As you Know the Black/ Yellow is the Ground wire for the bike. If the Rectifier has bad Diodes it can melt wires real easy as it is not fuse protested. You can test that with either a Ohm meter or test light. But sort out the other issues with it un=plugged for now, just in case.
Sometimes you can have a problem where the Negative battery cable is not making contact, which is what the starter motor needs, and will find the ground through the harness instead. All that Starter Current going through the small ground wire, ouch.

The Brown wire which melted at the R/R plug, is ignition power, it runs through most of the bike supplying power to the gauge lights, brake switches, etc. It runs through a terminal in the Ign switch, and the R hand control. On/ Off/ Run switch. But at the R/R it is the Voltage Sense Wire for the 6 wire R/R system. It needs to see as close to Battery Voltage as possible, so it can charge correctly. If it sees a lower voltage do to circuit resistance it will overcharge the battery. If it is disconnected it will put out full output.
The PO was a Dip S*** for taking out the 20 amp fuse and twisting wires together, :sick:

Yes the PO was a complete nitwit.

At this point i have no power other then the oil pressure light with the switch on and the break and head light stop lights.

No other lights or ignition. Signal units click and activated but do not light up the lights in signals or in dash.

I have taken apart and checked the start stop switch and all other leads i can find and see. all seems well, and tested for resistance - checks out ok.

All leads seem to be good. I cannot see any disconnect or a missing ground.

The starter solenoid is not even clicking.
How\where should i check the ground of the starter motor?

When the wires burned out at the beginning, 2 of the wires going in to the rectifier were burned and one melted pretty badly - i soldered new wires as best i can.
Is there any chance the rectifier is completely dead? would this cause no starter or other no power?
How can i test the R\R?

Thanks!

you may have a damaged Ign switch.You can unplug it and do a jump around for each or the contacts to test. the series of contacts in each switch position is explained on the wiring diagram.
Ground for the starter, first is very mechanical, where it bolts to the engine. then the connection to the battery neg is the cable running from the neg battery post to the engine block. This handles the ground side of the heavy current load of the starter motor.

UPDATE: I have found and eliminated 5-6 shorts on the bike.
While the harness was undone and loose over the bike - i was able to get EVERYTHING working with no shorts.

So i figured OK i can put it back together. So i did, and as soon as i finished putting everyhing back together with a charged battery - no starter.

Everyting else works, except for the neutral light (bulb id good, and wire is good, i suspect the switch isent working properly). But - with the harness loom undone this was not a problem the starter switch worked fine.

So back to finding the next short.

OK - today i rolled the bike out the garage to clean up my work space, and just for kicks i put the switch on - low and behold - everything works!!!!
The nuetral switch was probably stuck in position and was not allowing the starter to run off the switch.

The bike starts and idles ok with my 200amp external power, but does not idle and runs rough when on battery only.
This battery did have MANY shorts and was pretty dead when i got the bike.

Would a bad battery cause rough running?

New battery is on the way in any case.

These bikes need a good,steady source of electrical power for the ignition. If your battery is questionable, have it load tested. Most bike shops and some auto parts stores can do this for you. They also need to do a specfic gravity test. This envolves using a glass tubed devise that has floating balls in it, they tell the charge condition by the number of balls floating.

If you don't have it load tested, you start the continual search for carb problems that may not even be there.