Interesting ignition coil issue (spoiler alert I think its cactus)

[OutbackPhil]

Well not too interesting. Was riding home the other day and the 450 conked at a set of lights. Thought the low idle had just conked it out. Light turned green, a few cars behind me. Hit the starter again, and she didn't want to start. Bit of choke just in case, still nothing. By this time I was getting some horn beeps from the line of traffic so I admitted defeat and wheeled it to the footpath. Long walk home pushing the bike as it turned out. A couple of times I stopped and tried it, thinking if it cooled down it might do me a solid and start. There were some hills coming up! Didn't want to start tho, didn't seem to even want to entertain the idea.

So pulled it down tonight, thought it might be a fuel issue/blockage, despite the fact it didn't start to splutter and die like it was starving of fuel, it just snuffed out (idle is a bit low it's got a wandering idle/hanging up RPM after pulling up at lights which I was just about to start searching for. Anywho, fuel in the float bowls, float bowls look clean enough, plenty in the tank, so save for a blocked fuel filter (unlikely) I guessed the fuel side was ok.

One of the plugs looked a bit black, one looked ok. Did a spark test, left side cylinder sparked fine. Right side, nothing. Swapped plugs, checked other earthing bolts for the spark test. Nothing at all. Noticed the right side ignition coil was getting quite warm to touch, yet the left was still cold (bike hadn't been run for a couple of days so there was no reason for the coils to be so hot after a short cranking duration).

Both coils were showing 0.06v with ignition off on a voltmeter. Ignition on, and left side coil (the sparking side) showed 11.8v. Right side coil, 1.15v. I thought I'd misread the decimal point location, but no. I didn't really have a point to measure the voltage going in to them, but the one wire comes of the CDI plug and splits into two to go to both coils so I'm not too fussed. Plus the good coil is nearly outputting 12v so it's going to be getting that input.

They were a 2nd hand pair of unknown parentage to replace the originals with frayed plug leads so I'm guessing one is dead. I'm a bit surprised (and anyone feel free to weigh in on this one) that it didn't simply run like a bag of *@%^$*@%^$*@%^$*@%^$ on the one cylinder (or at least want to run or start). It was backfiring super loud through the exhaust when the throttle was held wide open and I was trying to start it, but with throttle mostly or fully closed no backfiring; a couple of backfires through the carbs from time to time. I would have thought it would have been obvious running on one out of two cylinders. Am I way off?? Perhaps there's two separate problems with the bike??

I'll probably go for some aftermarket ignition coils, they're cheaper and as long as they fit fine I'll be happy.

Cheers

Phil

 

[OutbackPhil]

So some further testing on this one tonight gave me the following results:

Resistance on each coil between earth wire and 12v wire came to about 4ohms (can't find the specs in Clymers but I assume it's ok because they're consistent).

Resistance on each coil between earth and the HT lead end was about 22-25k ohms (again both fairly consistent).

Still no spark on the right side cylinder, with both frame mounting bolts becoming warm quickly on the non-firing right coil only).

But when I swapped over the individual earth wires within the deutsch plug between the coils and the CDI the non-firing problem swapped to the left side.
Interestingly the warming up of the frame mounts also switched to the left side coil.

So that would tell me the coils are ok, but that the problem lies elsewhere, possibly in the signal generator or the magneto?? Would anyone care to agree or disagree on this one?? I guess my next step would be to test the signal generator but after that I might be scratching my head a bit!

I'm open to suggestions for other things to test tho, if anyone has anything? Cheers

 

[Redman]

Hum.... no responce in 4 days.

I am not making any comment because I have no expereince with the 450 (nor any 2 cylinder), and I gather there are differences.
((four cylinder GSs have two coils, and I dont understand why the 2 cylinders dont have just one coil))
((and I am not familiar with a coil having a ground wire))

But in general, in troubleshooting, if you swap a component and the symptom moves with that component, well, then, the cause of the symptom is related to that component.
If you swapped the ground wire and the symptom moved to the other coil, well, then, your problem is related to the ground wire... somewhere... maybe the connector.... maybe the wire isnt really grounded. Trace out the wire and see what you find. Maybe the mounting that heats up is then carrying current because the coil lost its ground.
(I am taking you word that the wire in question is a ground wire.)

 

[OutbackPhil]

Thanks for that Redman. Hadn't thought of it that way. I'll follow the earths and see where they lead. Perhaps something has come loose (hopefully it has that means an easy fix when I find it). I thought the coils might have earthed onto the frame (or part earthed) but none of the wiring diagrams show they do so I guess the frame is simply a mounting point for them. I'm assuming the igniter is ok for now, but I guess I'll have to test everything if nothing jumps out at me.

Back to it

Phil

 

[Redman]

Any 2 Cylinder guys that can help here.....??

 

[GregT]

So some further testing on this one tonight gave me the following results:

Resistance on each coil between earth wire and 12v wire came to about 4ohms (can't find the specs in Clymers but I assume it's ok because they're consistent).

Resistance on each coil between earth and the HT lead end was about 22-25k ohms (again both fairly consistent).

Still no spark on the right side cylinder, with both frame mounting bolts becoming warm quickly on the non-firing right coil only).

But when I swapped over the individual earth wires within the deutsch plug between the coils and the CDI the non-firing problem swapped to the left side.
Interestingly the warming up of the frame mounts also switched to the left side coil.

So that would tell me the coils are ok, but that the problem lies elsewhere, possibly in the signal generator or the magneto?? Would anyone care to agree or disagree on this one?? I guess my next step would be to test the signal generator but after that I might be scratching my head a bit!

I'm open to suggestions for other things to test tho, if anyone has anything? Cheers

It's difficult to follow with some of your terminology...
"individual earth wires" Do you mean the wires from the ignitor to the coils ?
If those are the wires you're swapping, and the coil and mountings get hot, then there's current flowing from the ignitor which IMO shouldn't be.
Which suggests the TCI (not a CDI) has developed a fault on that circuit.

Borrow a known good TCI and swap it in.

 

[Gorminrider]

yes, you might have a TCI problem...but check the signal generators too. (they are under the crank's small cover..) Your symptoms suggest One might be disconnected, faulty, etc. They are supposed to act somewhat the same as points, they tell the TCI when to spark. No signal=no spark.

By the way, there's no magneto in these bikes. Just a generator that supplies lights AND ignition power.