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first post here, be gentle :)

I have an (presumeably) electrical issues with my '94 Kawasaki ZZR600 (ZX6). Two weeks ago, I was ready to go to work when suddenly the bike died on me, all electrical power was gone. This happened right after starting the bike. At first I thought about a short/blown fuse, but after waiting a while and turning the key again, power was back. Weird. Fast forward to a trouble-free week later, when the same thing happens, and the bike just completely dies during riding, on my way to work. On the way back home, the bike stuttered violently and rocked me back and forth on my seat. I avoided the highway and take the scenic route home, but the bike seemed to lack power. Also, when the bike was running poorly it almost threw me of the seat, and I could clearly hear a very loud bang coming from my exhaust, similar to when incomplete combustion occurs (running on three cylinders maybe?)

And then this happened

Back home, I expected all my wires and lo and behold....every connector between regulator/rectifier and alternator have MELTED.

enter image description here

More Pictures here

So in short, symptons

  1. Starts very poorly, but (used to) run fine afterwards
  2. Dies completely (loses all electrical power), only to come to alive again a few minutes later
  3. Stalls during riding
  4. The bike violently rocks me back and forth on my seat, like the ignition is completely off
  5. Connectors between regulator/rectifier and alternator are fried, reg/rec unit and junction box are toast

What I've done soo far

  1. I've checked my fuses and measured the battery voltage before, during and after starting the bike, all seemed fine.
  2. Inspected the regulator/rectifier and junction box, by using the method described in my Haynes manual. Both units are defective. The alternator itself is fine.

Questions Since I'm curious as to what has happened and what's the best option to fix it, I now have some questions:

  1. Regarding the cause of all this: I suspect that the reg/rec unit has died, so the alternator couldn't get rid of the higher voltage, thereby melting wires and frying components. Does this sound plausible, or is there another explanation? Maybe the problem originated in the old wiring and connectors?

  2. Why didn't any of my fuses blow? Aren't they designed to prevent exactly this kind of damage?

  3. The connectors between alternator and reg/rec unit are gone. The junction box also took a hit. I have yet to check the other electrical components, but can I expect more damage?
  4. I've already found a new reg/rec unit and alternator and plan to replace the affected wiring and connectors, but would this be sufficient and a good way to fix my damage or is there something I could do better?

I realise this is a long post so thanks in advance for sticking with it so far, and hope you have some ideas to help me. Thanks in advance!

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    Are the contacts in the wiring connectors badly corroded? Corrosion creates resistance which creates heat. Also could cause intermittent connection issues.
    – Mysterfxit
    Apr 13, 2019 at 3:29
  • It's a little hard to tell since the overheating has damaged the connectors, so it's hard to say if they were already damaged or not. But, judging by the state (and age) of other similar connectors I'd say yes, I would guess they were corroded.
    – Joris Janssen
    Apr 16, 2019 at 11:24
  • What does the charred connectors' wires connect to? Is it the only one that over-heated?
    – Mysterfxit
    Apr 16, 2019 at 18:22
  • The charred connector you see here connects to the regulator/rectifier. If you click the imgur album, you can see other charred connectors as well; they connect the alternator output to the wiring harness. The last picture (red connector) seats the main fuse and starter solenoid. It looks like everything in the path between alternator and reg/rec is charred.
    – Joris Janssen
    Apr 16, 2019 at 19:54
  • I meant specifically which wire is the burnt one. I can see three yellows, a black/yellow and white. I'm guessing the three yellow wires go the free end of coils on the alternator and the burnt one is the common one.
    – Mysterfxit
    Apr 16, 2019 at 20:27

2 Answers 2

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I'm going to say the heat was caused by a poor mechanical connection causing arcing or possibly high resistance due to corrosion in the connector or somewhere else along that path in the circuit.

This post shows a similar problem due to a poor mechanical connection:

https://www.vfrdiscussion.com/index.php?/forums/topic/64040-that-famous-burnt-up-white-rr-stator-connector/

You probably back-fired when the ignition power was cut and unburnt fuel went into your exhaust, then the ignition came back and the next exhaust cycle ignited the fuel in your exhaust system.

1) I think the old wiring and connectors killed the regulator/rectifier. When regulator goes your battery is usually the first victim by over charging or under charging.

2) I don't think the AC circuit is normally fused. If it shorts to ground the only thing that happens is no electricity is generated.

The ignition kill switch on my Vespa literally just shorted the run coil to ground. (And sometimes in the rain through my hand)

3) Make sure all the connectors are free of corrosion and inspect for burn marks from arcing. If you find a bad mechanical connection you can't correct some people eliminate the factory connector and make hard-wired connections.

I was constantly blowing the main fuse on an old Honda. The fuse holder was even getting a bit melty. I fixed it by cleaning all the contacts in the connectors. They were all visibly corroded. I used an aerosol product called DeoxIT.

4) With the above I would think it would be sufficient. You may even want to inspect your ignition and run/stop switches and ground connections if you haven't.

Obviously Once you're running keep a close eye on it to see if it's still overheating.

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I think you are right! I've inspected the entire wiring harness and a lot of connectors look crusty, rusty and just very bad. I've dug up another wiring harness and I'm in the process of replacing my old one, cleaning everything I find on the bike as I go, tackling all issues in one sitting. Thanks for the help!

So, summarized:

  • My bike died, lost all electrical power
  • Old age and keeping the bike has corroded many connectors in the wiring harness
  • Higher resistance caused the wires to melt, destroying components in the process and messing up my ignition, causing the bike to shut down and stutter

To fix: - Replace wiring harness - Replace all bad components (reg/rec, junction box and IC unit)

Again, thanks for the help!

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