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Discussion Starter #1
Hey guys looking for some input, I've had a CX500 for about six months now, it was running fine up until I put her away yesterday night, I went to start it this morning and have determined that neither side is sparking.
I looked into electrical tests I could do on the forums here and went through one that tests the resistances leading from the stator to the CDI and coils, I think. (Took apart two connectors under the seat, one an 8 plug with 1 empty, and one a two plug) all of the resistances were well within specs, or at least what I could find to be "spec". I then found an interesting test that said you could test the voltage coming out of the CDI to the ignition coils by reading the pink, and yellow lines that come from CDI to Coil and ground. I performed this test and it only ever showed at most 4 to 6 volts on either line. (Pink to Coil and Yellow to Coil both with end on ground) Could this mean my CDI is the issue?
Also I check the battery to be safe, it read 12.3~12.6V sitting, no load. I also have swapped out to new plugs, just to try that route too.
Thanks,
Nigel
Bike is a stock 1980 CX500C Custom.
 

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A sudden failure like this says "kill switch" to me.
 

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Discussion Starter #3
I suspected that at first too, so I looked into the handlebar switch its' self but didn't see any wires loose or cut. Is it possible for the switch to fail without visual signs, and if so do you know of an easy way to test to see if it is the switch, I'm still searching down a wiring map for it so I can try and isolate the switch out.
 

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You can try starting it with the black/white wire from the cdi disconnected. That should remove the kill switch from the troubleshooting steps.

I'm going from memory, though, no access to my bikes or fsm. Anyone else?
 
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Cdi could be the problem as well, but the sudden failure smells fishy.
 

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Just for curiosities sake, have you checked the clutch free play adjustment?
If it gets too close to not disengaging when the lever is released it will not engage the intelock and you will have no spark.
 

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I then found an interesting test that said you could test the voltage coming out of the CDI to the ignition coils by reading the pink, and yellow lines that come from CDI to Coil and ground. I performed this test and it only ever showed at most 4 to 6 volts on either line. (Pink to Coil and Yellow to Coil both with end on ground) Could this mean my CDI is the issue?

Bike is a stock 1980 CX500C Custom.
This looks like the smoking gun to me. You should be seeing voltages up around 150 from the CDI on both of those leads. A for-sure test would be to borrow a working CDI from someone and swap it in. I'm fresh out of spares at the moment, but perhaps someone else on the forum has one they could loan you. If you don't have any luck finding one, I've got a Finnbox I could send you temporarily. Nuisance there would be shipping charges back and forth US to Canada.
 

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I knew if I kept commenting, someone who knows something would get involved. :)
 

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Test the white wire TO the CDI in the same manner outlined above for the pink and yellow wires coming from it.

If you get the same voltage on the white wire as on the pink and yellow wire the stator is fubar.

If you have 100 + volts going in but 6 coming out the CDI is fubar.
 

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Make sure the wiring around the CDI is good. Could be as simple as a loose or corroded terminal.
Check all the simple things first.
 

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Discussion Starter #13
Tried out some more of the tests today,
Started with a simple continuity test on a lot of stuff, all of them came up good, next moved on to the kill switch, did a continuity test on that : Green Wire > Black/White; on the connector located behind the Honda emblem right on the front forks, it came up with what I think is correct : switch on - no continuity, switch set to either off position had continuity. Next I rechecked the resistances from the stator to the CDI all of them were in good standing according to the numbers I can find online except one, the Source Coil Low Speed, it was about 40 ohms less than what the numbers said it ought to be (344 ohms measured). I am unsure if that's enough to kill my spark or not. Lastly I did a voltage check on the White wire TO the CDI. (the one on the two wire connector Blue + White) It showed the same voltage 4~6 V as the CDI to Ignition Coils did, (pink + yellow) I'm not the most skilled on the electrical side of things but I tried as much common sense stuff as possible; I also checked the clutch switch, which was engaging and disengaging normally. Looked around in-case there was anything loose but found nothing that seemed off.

Is it possible for a failure in electrics to suddenly happen without any real warnings?
I did have the bike out and running the night before all of this started so it seems odd to me that it could just stop working. The only thing I did notice were a few misfires and backfires on engine braking, but that happened to me all the time which I thought was fairly normal for a machine of this kind of age.
Cheers,
Nigel
 
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