81 400 died strangely

adam2189

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Hey guys, so I've been researching and fiddling for over a week now and am finally resorting to starting a new thread...

I was riding home one night and everything was completely fine. All of a sudden my headlight, the lights behind my gauges and engine all died simultaneously. I grabbed the clutch, still rolling, and tried hitting the starter...nothing...so I let the clutch out, engine turned over freely but no fire or headlight or gauge lights. Something shook loose? Battery dead? I ask myself as I coast to an optimally placed street light to see what's going on.

I pull the headlight and check wires, remove seat check wires, fuses (blade fuse conversion forever ago), check battery, etc. Now here's my immense confusion: the neutral, oil, and turn signal lights work on the cluster, the blinkers work, the license plate light, brake/running light and horn all work. Jump the starter solenoid and the starter turns over but no spark (plug against head in boot to check). I've looked, researched, and stared at the wiring diagram for days now. I'm stumped...and it was 75 and sunny here today.

Does anyone have any suggestions or similar experience? Also sorry for the novel. Thanks! Adam.
 
Check the ignition switch. I had similar issues and it was corrosion in the switch. The switch isn't difficult to take apart, just be careful for springs...
 
Thanks for the quick response! I took apart the kill switch and it is clean and corrosion free...I didn't check the connector for corrosion though. I'll check that and try to jump the 2 red/white wires at the connector. My head hurts from looking at the rainbow of lines that is the wiring diagram.

I assume you mean the kill switch when you say ignition switch? In looking at the diagram it seems that the keyed ignition switch simply completes the power circuit to everything. Since, when the key is on, all the lights besides the ones mentioned above come on I assume it's doing it's job and completing the power circuit. Meaning the power delivery is bad somewhere else. My first thought was the kill switch, but I hadn't thought to jump it at the connector. Am I missing something about the keyed ignition switch? ...like I said all the colors are making my head hurt.
 
The headlight, signals, and spark(ignition) are all off the same line before the fuses. So if you are sure the fuse box is all connected right, and the fuses are good, that leaves only a few possibilities. Do you have a multimeter? If you do, you should be able to figure this out pretty quick.

You know the problem is on the ignition line out of the fuse box. You aren't getting power to the starter solenoid from the start button. You say you checked the engine stop switch(off/run/off). With the bike power on, see if you have voltage going in to that switch, and coming out. That's the proper way to check it, instead of just eyeballing it. If you have power in and out of that switch, then I don't know what to tell you. The safety relay, if bad, will prevent you from using the start button. But if that were bad you'd still get spark when jumping the starter solenoid. If the TCI is bad, that would prevent you from getting spark, but what are the chances of that going bad at the same time as the safety relay? I suppose it's possible, but unlikely.

First thing first, recheck that off/run/off switch. The start relay, coils, and TCI all get power off that switch, so it's only logical.
 
This is the wiring diagram I'm using:
full

It looks like there are two different sources, one for ignition, one for headlight etc. the only common i see is in the kill switch. I do have a multimeter and will check everything again this evening. I think I just need to go back and go through everything again, ugh. the joys of electrical systems from the 80's. I'll update if anything changes. Thanks again.
 
That's the one you want to use.

Our electrical on these old bikes is actually pretty ingenious, and somewhat simple compared to Honda's from the same time frame.

Problems tend to arise from people poking around and changing things they shouldn't, as well as the fact that a lot of these bikes sat dormant for 15 years or more in the elements. wire and connectors were not meant to survive that long with no maintenance!
 
Samething happened to me couple weeks ago and it was a blown fuse because of a bad contact in the headlight bucket ! A bare wire was touching the metal of the bucket causing a electrical issue .
 
Didn't get a chance to look at it tonight, I'm in the process of moving so this was the "perfect" time for this to happen, haha. Thanks again for everyone's input. Hopeful Wednesday I'll get a chance to look for shorts, corrosion and go back through and check everything carefully.
 
finally got a chance to get into it last night. It was indeed the kill switch wires, red/white. Although it wasn't immediately apparent. I was getting sporadic voltage at the kill switch and found the harness inside the headlight to be causing it. For some reason the connector inside the plastic harness had "welded" itself together thus causing an intermittent connection that would show voltage then no voltage. I had to cut the wires and bullet connect them back together. It took a pair of pliers to pull the plastic harness apart, it didn't break but the metal connector inside snapped in half. Cleaned all contacts and refitted them with dielectric grease while I had everything apart. Electrical fixed...for now. Always a project, never perfect. That's what makes it fun though!

Thanks again for yalls input! It helped immensely! Now I can enjoy this 80 degree fall day.
 
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