1982 KZ750 electrical issues

Greetings,

First real post here. I did some searching and didn’t quite stumble across an answer.

A couple weeks ago I picked up an 82 KZ750 4. The guy I bought it from had gone through the wiring and gotten the rear blinkers to work. It came with a shop manual, he’d done a lot of service and minor repairs to it. Good guy, we spoke a bit, seemed pretty competent. I don’t question his work on the bike. He said he put about 1500 miles on it. Selling because of hard times and new job hasn’t started yet.

I trailered it home 150 bumpy miles. The next day I went on 3 low speed rides around the block, about 10 miles total. On ride 2 and 3 the motor started struggling a bit at lower revs. Felt like the engine was dying. Rode it home, wouldn’t restart.

My cousin is a Mercedes tech with a few years of auto schooling. He helped me with understanding the service manual wire diagram and we used a multimeter to check voltage, it stopped at the ignition harness. I disassembled it, cleaned up the contacts, and had continuity through all the wires. Ordered a replacement ignition, hooked it up and still wouldn’t turn on. If I jump the white wire (power) to the yellow wire (start/stop) the bike fires right up using the start switch and runs fine. Kill switch works as well.

Rechecked the fuses, still all looked fine but replaced with new ones matching the amps listed on the fuse box. Checked all wires connectors are old and tarnished but the wiring looks ok for the most part. Did find one melted black wire in the front left turn signal that was not connected to anything. That signal had been working fine and I never smelled anything burning. The right side has the matching black wire unconnected as well and it’s not melted.

After replacing all the fuses tonight I reconnected the original ignition switch and turned the switch on. I tried the the turn signals again, the rears were the only ones connected and they did work this time. Tried the start button, bike fired right up. Routed the wiring back into the head light assembly, connected the headlight, tried firing it up again to test the head light, dead. No response from the the start button. Tried the turn signals, slow pulse but did activate on the left side. Right side would not activate. They really seemed like they were struggling to activate. Checked fuses, all intact, swapped out the main 30amp anyway, blinkers struggled to come back on and would work briefly but not the start switch.

Jumping the white and yellow still fires right up.

The positive side battery cable has some frays right before connecting to the battery. The negative side is a little dirty but is not frayed.

I have tried 2 different batteries that were topped off with a battery tender. One was 4 months old taken off another bike.

Ideas? And thank you in advance!

Grab your meter
everything must be connected

meter on DC V
Ignition on/engine off
Black probe on negative battery post( post will be the metal part of the battery)
Red probe on positive battery post
Note voltage

Move Red probe to the white wire in the green box.
Back probe the connector as you don't want to separate the connector.
Probe it on the ignition switch side of the connector.
This will test the white wire from the battery to the red probe.
If you have more than a .5V drop from the first reading (battery) then you have high resistance on that wire.


Then move the Red probe to the other wires in that connector but probe the other side of the connector(the battery side not the ignition side)
Note the readings

Turn off the bike

We'll start here first.

sorry, got distracted, the rain stopped--so i went outside to work on the bike..whoops
not really hitting the Ginkgo Biloba.. more like iced vietnamese coffee with milk


photo: www.classiccycles.org/media/DIR_1653304/...ffff84f8ffffe41e.jpg

Where is the green box? Thanks for the help.

F64 typically post a wire Schematic with highlighted color coded areas to guide you to the proper wires to test. It appears either it didn’t post of he needs to refill his Ginkgo Biloba :woohoo:

Tested the battery that was reading over 13 volts the week prior, showed 6.7v, swapped it out with one reading 13.4v. Soon as I did that I connected only the 6 pin ignition harness, blinkers worked, bike started right up. Took a few readings.

Ignition on bike, off at Battery 13.4V, motor warmed and at idle 16.9V. Slight revving put it 18+. (Reg/rec issue there, seemed kinda high?) Turned it off and reconnected everything for readings at the ignition connector. Now it won’t run again.

Now at battery: 12.6 Ignition off
12.6 ignition on

Ignition on: Male side of 6 pin connector at the front of the pins:

11.5 white
11.5 black and white
0.0 at other 4 pins
0.0 at single brown wire

Couldn’t get any readings back probing from male connector or female connector and no readings at the back of the ignition switch.

Right away it looks like there may be an issue with your ignition switch.
I'll look at it more once I get to a computer.

I’ll plug in the brand new one and check readings.

Brand new ignition switch:

Battery 12.5

Ignition off/motor off. Connected ignition 6 pin with female side back probe:
White 11.4
Black and white 11.4
Yellow, blue, red, and orange 0.0, single brown wire 0.0

Ignition on/motor off 6 pin plus single brown wire connected back probe on female connector:
0.0 on all 6 pins and brown wire.

Ignition on/motor off/brown wire disconnected:

White 0.4
White/black 0.4
Yellow 0.4
Blue 0.0
Red 0.0
Orange 0.4

Same conditions tested at the back of the ignition switch:

White 0.5
White/black 0.5
Yellow 0.5
Blue 0.0
Red 0.0
Orange 0.5
Brown(though still disconnected) 0.5

Your readings seem off.
With the ignition on/Engine off
You should have
12v white
12v yellow
12v brown
12v blue
12v red
12v black/white
12v orange

Ignition off
only 12v on (white) and (black/white)

Is your meter on DC V?
all connectors connected?
black probe on negative battery post?
and positive probe on the various pins of the connectors?

How are you able to start the bike?

Photo shows settings used on my multimeter. Black probe is on the negative terminal screw dead center. Red probe is used at all other contact points.

All connectors are connected.

I can reliably start the bike by connecting a wire to the male end connector of the 6 pin that plugs into the ignition harness using jumping the white wire to the yellow wire.

I had a random start 2 days ago when I replaced all the fuses. Had another random start yesterday when I swapped batteries out.

That’s part of the problem I’m having diagnosing, inconsistency in results.

Video of testing ignition on, motor off, brown wire disconnected, probed at the back of the ignition switch. Never mind the 3 year old singing in the back ground.

Never mind. Won’t let me upload.

This shows jumping the white to the yellow.