80 KZ1000E - no spark on #3 and #4

Hello all,

I have no spark on #3 and on #4. Doesn't make much sense to me as coils are hooked 1 4, black and pink on left and 2 3 green and pink on right. Plugs are clean and gapped, but they are the old plugs. They look fine. As I remove spark plugs while running 1 and 2 affect the idle. #3 and #4 had no spark and no effect when removed.

It will back fire every once in while and I assume that is gas collecting in number three or four to hot enough to pop. I suppose I will test #3 and #4 wires for continuity. I replaced the spark wire but not the boots but all tested fine. The #3 and #4 pipes are far less hot and water does not instantly evaporate.

What order should I do things? Can a coil lose one output and not both? Could both coils lose one output? Perhaps IC ignitor or rectifier? Any help appreciated.

R
1980 KZ 1000E2

One way to test the caps and the wires coming out of the coils would be to swap the #1 and #4 wires so they are on opposite cylinders. If the dead cylinder switches from #4 to #1 there's very likely a problem with a spark plug wire or cap. If #4 is still the dead cylinder the caps and wires aren't the problem. Then try the same test by swapping the #2 and #3 wires to see if the dead cylinder moved from #3 to #2. Ed

Plugs and caps, they're old. If not bad they will be soon.
Steve

Are you sure you have no spark on 3/4? Swapping plug wires as Ed suggested is one way to check. If you've got a timing light, try the pick-up on each plug wire. I had similar symptoms, cold 3/4 cylinders with occasional backfires. The spark checked good. Turned out to be a split hose in the Clean Air system to the reed valves in the cam shaft cover. They are divided between 1/2 and 3/4. It was sucking in so much air that the mixture was too lean to fire.

The clean air system is gone and properly blocked off. Will replace the 35 yo caps and plugs. 1st things 1st. R