1981 750H electrical issues

I am not getting spark to the number 1 and 4 cylinders on my 1981 kz750H. I am thinking that it is probably the left coil but I am not 100% sure. I started thinking that perhaps there is a problem with the wires leading to that coil. I looked at the wiring diagram but I don't really know what I am looking at. Are there 2 sets of wires running from the battery or is there one set of wires that splits to 2 somewhere before the coils. Probably a dumb question but I wanted to make sure. Thanks in advance.

A quick check would be to switch the wires from coil 2&3 to 1&4 to see if you have spark. If you have spark, put the wires from coil 1&4 on 2&3 to check the wiring.

Do not do this with the spark plug caps attached to the sparkplugs unless you switch everything else around.

The coil has been tested and it is good, so the problem is somewhere else. Short of rewiring the entire ignition or taking it to a shop, what are my options? Where is the most likely place to look for the problem?

I did have one leg of an electronic ignition go down. It was an old Martec brand one and I had to spring for a Dyna. No easy solutions just re-check wires , connections and look for shorts. Meter your volts at all connections until you find the dropout.

If the IC igniter has a fault could it still work on two cylinders or would it just quit working completely?

I had this problem too, and it was one side of the pick-up unit that had an intermitent fault. Each side feeds two cylinders (either 1 & 4, or 2 & 3). I bought a used set of pickups on eBay, and the problem was fixed. A number of the other members here have had this problem before, with the same cause. If you search, you will probably find the old threads discussing this.
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Thanks for the advice. The coils tested good, condensers tested good, CDI box tested good(I am not 100% sure), wires are good, plugs are good(and gapped right). That leaves the pick-ups and what else? I am leaning towards it being the pick-ups but have had some strange readings on the Ohm meter.

osirus_4 wrote:

If the IC igniter has a fault could it still work on two cylinders or would it just quit working completely?

Solid state junk can fail in sections. It could easliy lose the drivers that run a single coil. You could try swapping and see if the spark follows the output line from the CDI.

I had a similar problem on my 81 650 CSR which is basically the same bike as the 750 LTD. After trying several different swaps with known good parts it turned out to be just a dirty connection where the pickup coils plug into the harness. Just follow the wires where they come out of the rt side of the crank until you find a small square 4 pin connector. Take it apart and clean real good. It could be something else but this would be the cheapest fix.

0sirus, Your answer kind of bothers me. First, you didn't say how the coil was tested. Then you say that the "condensers" tested good. You don't have any condensors. You say the CDI box tested good. You don't have a CDI box. You state that the wires and plugs are good.

I don't see any real analysis of the problem. I suggest you do the following:

First, test spark plugs... swap #1 and #4 plugs. If the non-firing issue stays in the same location, then the plugs are likely not the issue.

Next, swap the #1 and #4 plug wires. They come off the same coil. If the problem stays in the same place, then it is likely the problem isn't with the wires.

Next, remove the #1/4 coil and physically swap it (and the wires) with the #2/3 coil. The #1/4 coil has the primary leads that go to the #1 and #4 spark plugs. If the problem stays in the same location, the problem is with the IC Ignitor box or the pickup coil. It isn't likely that the problem is with the IC Ignitor box or the pickup coil because the problem would most likely affect the associated spark plug... that is, if the #1 isn't firing and your IC Ignitor is bad or your pickup coil associated with the 1/4 side is bad, both the 1 and 4 plugs would not fire.

Your problem is most likely with the spark plug, wires or the connection to the coil... that is why I put them first in the trouble shooting order. Check these things in the order and manner described and you will soon figure out what the problem is.

osirus_4 wrote:

Thanks for the advice. The coils tested good, condensers tested good, CDI box tested good(I am not 100% sure), wires are good, plugs are good(and gapped right). That leaves the pick-ups and what else? I am leaning towards it being the pick-ups but have had some strange readings on the Ohm meter.

I don't mean to sound sarcastic but I am not a master mechanic so my terminology isn't great at times, my mistake for calling an IC igniter a CDI box. As far as the condensers go if it looks like a duck I just assume that it is a duck, I will need to do more research to correct my incompetence. All the things that the above post stated have been previously done in pretty much that order. The coils were tested in a bike shop with the wires attached and me standing there. The IC igniter was tested using an Ohm meter and sending a current through it to the coils and both sides had a current go right through and the coils both worked. The plugs have been changed three times. When I try to send a current through the pick-up coils I get a reading through one side but not through the other, that is why I think the problem is with the one pick-up coil. I also tried to get the pick-up coil to work by running a screwdriver by the pick-up and only the one set of plugs sparked. The problem is that both #1 and #4 won't spark. I hope this cleared up some of the misunderstandings from my previous posts.