2/3 Coil only fires half the time!!! RESOLVED :)

Great looks like a decent one.
black in the center for these Ohm and voltage tests. Black would go in the hole on the left if you wanted to Test up to 10 Amps of current. the red stays on the right.
In about the 7:30 position on the dial there is a 30K Ohm scale. That should be the one to use for checking the wires. See if you can get a steady reading.

Ok, all plug wires tested the same, so they're good. I pulled the #2 and #3 plugs, and the #2 is wet with a gas smell, so I now know which cylinder is the problem.I will swap the #1 and #2 spark plugs and try that tomorrow. If the problem jumps to the other coil, then it's the plug.

OK, now I kind of got involved late on this.
Can you clue me in, did you check compression on all 4 and what was the #'s? Also If Compression is OK, have you made sure the Float valve in the carb is functioning properly? That would be to use a clear piece of tubing attached to the float bowl drain, routed along the side of the carb, pointed up. Then with the drain screw open and the petcock on "Prime/ or ON" so gas flows. Use the clear tube as a gauge to see if the fuel level is just below the gasket mating surface of the float/ fuel bowl, within 3mm. Not above it.
Does any fuel come out the carb overflow tubes?
Maybe you've done this before going to the ignition? If it is only 1 plug, it could be another issue.
Using something like this on the #2 while everything else is hooked up, would let you watch the spark. www.harborfreight.com/automotive-motorcy...rk-checker-4445.html
Inline spark checker

The only things that were not eliminated in the swapping tests were the actual spark plugs and cylinders, and possibly the plug wires, depending on if you swapped them or not. But they (plugs and wires) were new.

The final test we did meant it had to be the green-2/3 channel in the igniter, or the actual green wire.

You are no longer using the green wire, so that should be out.


There is a chance one side of the Dyna S is bad. You can do the same swap test to determine that.

Flip the dyna S rotor, and swap the small wires on the coils. If it's the Dyna S that's bad, the probem will move to 1/4. If it's the plugs, it will stay on 2/3.

You could also just swap the plugs.

BTW, after going back and reading the earliest posts... You know not to run the bike, or check for spark, without giving the spark some sort of path, correct?

Pulling a plug wire and just letting it lay there while running the bike can break down the coil and/or damage any igniter. There shoud be no more than 1/4" or so, gap, for the spark to jump when checking for spark. Just disconnecting the plug cap will lead to way too much gap.

That test could be done somehwat safely on old distributor cars because the spark could jump from one spark teminal to another in the ditstibutor cap. A bike doen't have that, so damage occurs.

Its very possible that he is just now fighting a plug that was fouled from the previous bad Ignitor. Everything else might be fine, hopefully that is all it is.
Also another way to check out the signal from the ignitior to the coil, would be a simple test light. Using the ground pulse from the, now Dyna, ignitor, and a 12v source. Light should of course blink as the signal is made. An O-scope would be beautiful for checking all of this. but not many have the access.
Go to love the simple test light. Of course I'm old school, had to use a test light and Ohm meter to diagnose everything for years.
That meter could also be used to measure "Dwell". Now that would be a very useful value to check on each side of the now Dyna ignitor.

Looks as though the meter you linked doesn't have a Dwell Measurement. Thats to bad as it would be a cheap test for you to do.

A scope with a 100:1 or 1000:1 reduction would work. But a test light only shows if the igniter transistor is switching on and off. It doesn't show high voltage breakdown which is a common failure. The igniter has to withstand up to 300 to 600v spikes under normal use. The protection is provided by high voltage zeners. When the zeners fail, the transistor still works, so it will turn a test light on and off, but will not hold up the 300 to 600v spike. This means the coils will turn on and off, but no inductive spike will occur.

The wave form will show up on a scope, so a scope can be used to see it, but you need special probes to reduce the high voltage. I could only see up to 600v spikes, but they could be higher. since they are such short duration, the probes likely attenuate the spikes. (It' like Heisenberg, trying to see the signal, alters the signal.) Dead Zeners will show the typical inductor signal (exponential rise and fall), whereas a good igniter will show an impulse spike when the igniter creates the spark.

Testing for a dead cylinder while pulling plug wires can easily pop an igniter (and coils). The Dyna S seems particularly susceptible to this and probably acounts for a good portion of the reported failures. This could also explain why the initial problem was found on 1/4.

I was thinking that the test light would just verify that the signal was there. Also the report so far was 1 wet plug, hopefully the Dyna is still good.
So it was the other channel, 1/4 that failed? now the problem is #2? Or 1/2?

Yes, if the signal was not there, then it would definitey be bad. (It just can't be used to verify the signal is good. A high-voltage-only breakdown will show good with a test light, but will produce no spark).

Originally it was 1 or 4, but I think after coils and wires (and plugs?) replaced, it was 2/3.

However, if testing was done like on old cars (pulling wires while running), the problems may have been induced from the testing. (As explained in the earlier post.)

Right now, I think we agree: swap plugs, and/or do the rotor-flip-test on the Dyna S (also described in earlier post).

Seems I remember you posting that the Dyna did not work well under low voltage, then of course many other issues for quick failure. He said the voltage at the coils was down 2-3v from batt voltage. I hope he didn't damage it. To bad, but it looks like his meter does not have a Dwell measurement. That would be all under load normal operation and inexpensive to confirm the trigger from the Dyna.
Pulling plug wires was never mentioned as I saw, either a spark tester, in-line, or just using the timing light to check for spark. So hopefully he didn't pull wires off when running.

It appears that the spark plug was either bad or fouled. I swapped it to #1 and had the same issues. I swapped the coil and pickup wires, and had the same issue. I put in one of theplugs I had previously removed and it sounds like it's running right....but don't worry, it was just for the test and I will replace it with a new one today. Strangely though, the tach still reads 1/2 the rpm, so I will give a difinitive answer after rewiring the kill switch and riding the bike. And since it was brought up...the only plug wire I had removed with the original ignition components was #4. When I did, there was no change in the way the engine was running, which is why I originally thought it was the #4 cylinder. Thanks for all your help guys. Hopefully the only reply I will make on this thread after this one will be saying that the spark plug fixed it.

~Clutch

I'll keep my fingers crossed.

Try the tach on 1/4 and see if it has the same issue.

The Dyna S dwell is so long that a tach may not be able to register the frequency properly. As long as the bike is running properly, we can probably come up with a small adapter to get the tach straightened out.

She runs great now! :woohoo:

Here is my run down of what I think happened:

I noticed a slight hesitation. At first (and this was for quite some time) at WOT. I passed this off as a carb or timing issue. Eventually the hesitation became noticeable at all speeds. My first diagnosis was that the spark plug wires were bad, as they were literally falling apart when pulling them off. I replaced those, and the coils. The hesitation was still there, and eventually became a dropped cylinder. My theory is that the IC Igniter was going bad for a while, and then failed on the 2/3 circuit half the time...probably soon to be all the time. So I replaced the stock ignition with Dyna-S (since I had bought the 3 ohm coils by mistake). I still had the issue, which turned out to be a spark plug that had been fouled by gas from not firing. All seems well now thanks to you guys. I learned a lot about ignitions, how they work, and fixing any issues. She runs smoothly, and sounds even better than before!

As for the tachometer, I was going to ask if it might read differently with the Dyna-S. Since I have an Acewell computer, I simply changed the settings to 1, instead of .5, and now it displays properly.

Now, I need to tear out all the 30 year old wiring and replace that. Luckily, I have a lot of experience with this sort of work (as well as troubleshooting), so my thread on that should simply be a project thread, rather than a "What the heck did I do wrong thread" like this one. Again, thank you very much to all that helped me figure this issue out!

~Clutch