Cylinders 2 and 3 not firing

[Phare Est]

I just took my '81 XS11 out of storage and quickly discovered that cylinders 2 and 3 weren't firing (the bike doesn't start at all). I removed the spark plugs and inserted them back into the caps to check for a spark (by placing th plugs against the head or the frame). The was no spark coming from the coil going to cylinders 2 and 3. When I switched the plug-ins feeding the coils, the plugs for cylinders 2 and 3 were now producing a spark but the ones for cylinders 1 and 4 were not. I checked the plug-in wires, lead wires and plug caps with an ohmmeter and everything is within speck according to the manual. Hence, the coils and the plugs are probably not the issue.

The next step was to test the ignition unit (TID14-04). I swapped it with a spare one I had lying around that was working perfectly late last season. No luck : the same problem persisted.

As for my battery, it's brand new and has 13.2-13.3 volts when fully charged.

Is there any way to check the resistance on the pick-up coil wires? Could the problem lie elsewhere (grounds? relay switches?)

Thanks for the help !

[Bonz]

You switch the primary leads and the problem switches cylinders. The only thing that you changed was which coil is firing which plugs. The coil is the only variable at this point. Everything before the coil and everything after the coil works when you swap the leads.

I may have missed something but it sure sounds like a coil.

[Phare Est]

You switch the primary leads and the problem switches cylinders. The only thing that you changed was which coil is firing which plugs. The coil is the only variable at this point. Everything before the coil and everything after the coil works when you swap the leads.

I may have missed something but it sure sounds like a coil.

Actually, I switched the plug-ins (one has red and white wires while the other has red and orange wires). I did clean the terminals with a liberal amount of electrical contact cleaner. Is it worth testing the plug-ins coming out of the harness with a voltmeter?

[Bonz]

LOL, I had a brain fart in just switching those leads going into the coils wouldn't be the test. Cutting up too much brush out in the yard in the hot Colorado Sun this afternoon!

Pick up coil wires coming out of the unit can be a problem. Because the plate rotates with the vacuum advance feature those wires crack internally. They may look good externally but get down where they come out of the unit and pull on the wires if the coating stretches then you know you have a wire that's compromised.

[Radioguylogs]

Based on your testing, it is almost assuredly the pick-up coils/pick-up coil wiring

[Phare Est]

Based on your testing, it is almost assuredly the pick-up coils/pick-up coil wiring

Thanks Radioguylogs. I changed the pick-up coil wires two years ago: looks like I'll have to go through all of them again. I did install a new neutral sensor switch (https://www.partzilla.com/product/ya...KM-82540-00-00) on the bike over the winter. Could that also be the culprit?

[Radioguylogs]

If a safety feature was locking out IGN, then all the cylinders would be dead.

Can't be the neutral sensor switch.

[Phare Est]

The issue is finally resolved. I opened up the wire loom coming out of the pick up coil and running along the engine. Two of the five wires had broken off the crimp connectors. I'm pretty sure it happened when I pulled on that loom while installing the neutral sensor switch. Anyway, I changed all of the crimp connectors and made sure they were properly heat shrunk. All cylinders are firing again 🙂.

[Radioguylogs]

Congratulations, and thanks for the report!

[skids]

The issue is finally resolved. I opened up the wire loom coming out of the pick up coil and running along the engine. Two of the five wires had broken off the crimp connectors. I'm pretty sure it happened when I pulled on that loom while installing the neutral sensor switch. Anyway, I changed all of the crimp connectors and made sure they were properly heat shrunk. All cylinders are firing again 🙂.

Good find and good trouble shooting my friend!