TOPIC:

1981 KZ1100 with electrical tachometer

While riding down the road I randomly lose power and tach drops to 0 rpms. I can keep the bike running relatively easily with throttle so I suspect I am only losing one coil. During this time the ignition is going in and out with the tach spiking back and forth matching the loss of ignition. My tach gets its signal off the 1&4 coil so with my handy dandy manual and its wiring diagrams I have narrowed it down to 3 possible culprits. The 1&4 coil, the ignitor, or the 1&4 pickup coil.

Because this problem is intermittent and doesn't seem to do it until the bike is warmed up and under a load I am dreading trying to diagnose it. Where do you guys think I should start? Since even with the tach sitting on 0 and a huge loss of power on the bike I can continue to accelerate. That tells me I'm getting good fire on one coil and just losing 1&4 so would that rule out the ignitor? Does any of these symptoms sound like a classic failure of one of these parts? I have my fingers crossed the problem part has a bad measurement and this doesn't turn into a classic electrical gremlin that causes my hair line to recede further than it already has.

Are you running stock coils?
I've seen Dyna coils run into the same issue when the supplied wire connector (the clamp/guillotine type) intermittently loses connection and cuts power to one of the coils.

Yep stock coils. First thing I did was verify the wiring was all intact on and around the coils since I had an issue with that wiring when I first received the bike. If it is a wiring issue it isn't an obvious disconnect at the coils.

Try running it in the dark without the tank, wiggle some wires and watch for sparks to see if anything is shorting?

Also check the spark plug lead ends for corrosion. If found nip 1/4" off the ends and screw the caps back on, reconnect the coils too.
Steve

Could result from too high fuel level in #1 or #4 carb allowing running okay until warm and then one of the plugs fails due to excessively rich mixture which breaks the secondary loop whereby neither plug fires (no combustion in either outside cylinder) .

Would perform clear tube tests and assure fuel levels are within specs.

Would also spin over engine with plugs removed to hopefully see fat blue sparks, which indicates a strong ignition.

Could also try leaning the pilot circuit a little bit. And assuring that there's not a loose main jet.

Good Fortune!

Could this be an electrical problem? May want to check your battery voltage with a multi-meter. Check for 14.0 Volts DC @ 1500 RPM's or higher.
I've seen ignition systems cut-out before, when the voltage drops below 11.0 Volts.
Also, make sure your circuits have a good ground. Even a loose battery cable can cause probs.

Had a similar issue some years back, but in my case the whole bike would shut down. The 30A main fuse would blow after becoming loose in the retainer clips. Cleaning contacts helped some, but ultimately the problem was straightened out when the rotor, stator, and voltage regulator were replaced.

I would suggest, if possible change which coil fires which set of plugs. If the problem moves to 2 and 3 then it is most likely the coil, if it stays on 1 and 4 it is not the coil and you will have to look else where to solve it.

The weather allowed me to get to the bike today. I figured I would go for easiest first so I popped the timing cover off to check the ohms on the pickups. Getting something like 460 on one and a broken circuit on the other. Checked out the wiring and the one showing open circuit is infact the 1&4 pickup

And it appears to be the factory pickups. So I believe I'm gonna start off by replacing my 38 year old ignition pickups. I dont have $120 to fork out for new ones atm so I will update this thread when I get my hands on new ones and test them out.

I'm not sure this would be financially possible, but I think you can go with a Dyna-S - ignition system. Just in case the old one is too far gone.
Just a suggestion.

That's what I plan to do is go with a dyna s ignition module. I cant find an OEM replacement for the pickups and used ones run just $30 less than a brand new Dyna S. I'll order it this weekend and post here if that does end up being culprit. It was so easy to find I'm worried its pulling a fast one on me lol