Intermittent engine fault

Have you checked your spark plugs? Are a couple of them they sooty, or are they all running about the same? Can you tell which cylinders misfire? Ed

Sounds like you are getting weak or erratic coil firing. Let's split it into two things. Your coils rely on two things, your battery and your ignition. The coils have to be at a certain potential (voltage) in order to pack the punch needed to fire the spark plugs and they need the properly timed switching from the ignition to cause that punch.

Scenario 1: The electronic ignition is failing, and this is exacerbated due to heat. The pickups will fail when they get hot.
Ride the bike with the points cover removed. See if the problem goes away or takes a lot longer to appear. If it does, it's your pickups or igniter. Ditch all of that and get a Dyna S and get new Dyna wires too. For S&G, you can get a can of spray electrical contact cleaner and spray your ignition parts to cool them down when you expect the problem to appear and see if that does anything. If you are to that point though, might as well be ordering some parts. I got an old GS550 to limp along for a few weeks that way in my youth...

Forgot to mention grounds. Make sure your grounds are in good shape and are clean and tight! Not just battery ground but all of the other ones, too!

Scenario 2: Your coil voltage is probably being dropped somewhere preventing the coils from having the needed punch. Follow the current path from your battery to the coils and you will see all of the connectors and switches that could be contributing to this. Some guys, myself included, have wired in a relay to bypass all of that and get battery power directly to the coils and ignition but that's another story.

Hell, it could be both things. Gotta love that vintage stuff!

KBillZ wrote: 1980 KZ550 with '81 EI
I got my coils and installed them...seems like it's heat related. It's only ever done this once when it was cold.
I'll describe the symptoms again. When I ride my bike it runs great until I shut it off and restart it. Then it seems to drop two cylinders. It will start running fine again at no particular time or reason. I've gone through quite of bit of diagostics trying to find it. I'm going to install another IC igniter and see what happens.
What's frustrating me is that by the time I get my bike to the side of the road, the symptoms go away. I get on my bike and ride and they come back! arrrgh!
I have one question. If the ignition switch is faulty, could it reduce voltage enough sometimes to make these symptoms?
If my coils weren't ancient, I would feel as though I wasted my money.....
Any tips would be greatly appreciated.
Bill

Forgive if already suggested.

Use clear tube test to assure correct fuel levels.

Clean, clear, unobstructed air filter, and not over-oiled (if applicable).

Assure correct valve clearances.

Is battery weak or running down while riding?
At idle rpm, voltage across battery terminals should measure 13+ volts.
At 3000~4000 rpm, voltage across battery terminals should measure 14+ volts.

Assure integrity of connection where the negative battery cable attaches to rear of engine.

With ignition switch ON, voltage measured at ignition coil primary terminal should ideally be the same as voltage measured across the battery terminals.

Good Fortune!

Pilot circuit may be too rich. And tending to fuel-foul the spark plugs.

Thinking carbs are manual slide with side-located air screws.

Could experiment by turning each air screw out counter-clockwise, say 1/2 turn, to achieve leaner part-throttle condition. Then test ride to see whether it makes any difference.

Good Fortune!

If your bike the Kawasaki supplied electronic ignition, do this check out procedure of the pick up coils:

Ohm Checking Pickup(Pulsing) Coils

The pickup(Pulsing) coils on the Kawasaki’s with the factory supplied electronic ignition can sometimes fail or become intermittent due to heat and vibration.

1.Trace back from where the pick up coils are mounted,(BEHIND A RIGHT SIDE, CD SIZED COVER) locate and disconnect a small 4 pin connector. Using a multi-meter set on OHMS and range of 2K, check between the BLUE and BLACK wires(#1 and #4 sparkplug wires) for between 360- 540 OHMS.

2.For #2 and #3 sparkplugs the wire colors will be YELLOW and RED, again 360-540 OHMS. The 550’s,650’s & 750’s may be backwards to the Z1’s,Kz900’s,Kz1000’s & Kz1100’s.

3.If the pickup coils are suspect of failing due to heat, they can be stressed using a hair dryer without the need of the engine running.

4.A replacement set of pickup coils might be obtained from a dealer who serviced the police Kawasaki’s.

5. If replacement pickup coils are not available, your next choice would be to order a Dyna “S” electronic ignition system from www.z1enterprises.com It replaces the IC igniter with a smaller module located where the mechanical ignition advancer was mounted.

6. Checking with Kawasaki.com website has determined that the Pick up(pulsing) coils are available . The pulsing coil # is 59026-1133 and replaces the older # 1002, 1012 which were used from the MKII motors until the 2005 P24.

7.Check the small 4 pin connector that the pickup coils connect to for corrosion/loose pins too.

Make sure the air vent on the fuel cap is open. Mine kind of did that. Just take the cap apart and check the little pin hole for obstructions.

Thanks folks,
That's a lot to absorb but I'm on it.
I've done quite a lot of what's been suggested already but I'm going to pursue the idea that heat is the culprit and affecting my igniter or pick-up coils. I like the hairdryer idea. Getting it to fail when I have the bike on the center-stand would allow me to pinpoint what the problem is.
I have an extra pick-up coil....
I have a used ingniter on the way....
I'll be all over this thing with an ohmmeter today.
Thanks,
Will let you know how it goes.
Bill

Did a lot of diagnosing today, but can't say I've found the problem or at least the source of the problem.
I went through the entire wiring from the ignition to the stop/run button and all the connectors under the tank. I found what I thought might be the problem in that the voltage at the red/white wire is 11.6 or so and battery voltage is around 12.4.(with ignition on, lights etc.) Looks like there's some resistance somewhere, but I haven't found it yet.
I tested the pickup coils using a small torch to heat them up while on the ohmmeter. I had initially around 440 on one and 480 on the other. Well within the given range. As they were heated, the ohms went up and one side went over the 540 limit. Somehow, I think that 544 ohms probably would not cause it to fail, but I could be wrong. The resistance does, however rise with temp and I assume that is the normal state.
The idea of a relay is appealing right about now.
Bill

You don't need the "Relay", you need to find the voltage loss. Resistance does this. Start at the Battery, then the fuse panel, following the harness along each connector etc. Probably the main fuse or the wires right close to the fuse clips. But could be one or more of the switches. The ignition switch could be an issue.
but the real problem, is the intermittent cylinder loss. Try using a test light, once the problem shows up. Hook between the coils primary wires and see if it flashes when either cranking or running. It should flash as the Ignition coil is fired. If it doesn't then see if the 12v feed is there on the red wire. Then if the 12v feed is there on the red, and no flashing, I suspect a bad pick-up coil. But it could be the Ignitior. Member Loudhvx has a good test to determine which one. This is done by switching both the of the wires going from the pick-up coils to the ignitor, and also the wires to each of the ignition coils. If the problem moves, then the pick-up is bad, or if it is the same, then Ignitior. This is after trying the coil and lead swap, which I think you've done.

Unfortunately, if it is an intermittent pickup, that will be a difficult to diagnose problem unless you can identify exactly which cylinders are not firing.

The heat test you did seems to show they are normal, like you said, the resistance should go up quite a bit with heat. Vibration is the one part missing from the equation, so the pickups could still be the cause.

As Motorhead stated, it is important to find the missing voltage since it will cause other problems in the bike, like over-voltage to the battery, which will shorten battery etc.

The most common culprit are the fuse holders. If they look discolored or burned, that is likely the cause of the voltage loss. In an extreme case, I suppose it could affect the ignition as well.

I think I'm a reasonably good bike tech, considering (no formal education at it), so the problem I'm having would likely be the same for most of you. It just won't run crappy when I want it to and I need it to so I can pinpoint the problem.

It's probably going to be down to swapping parts until the problem goes away.

But, recent suggestions gave me a bit of an "aha" when the fuse box was mentioned. It has given problems before......

I'll keep ya posted...

Thanks for all the help.

Bill

My bike started running like crap just as I was coming home from a short ride yesterday. It stayed running that way long enough to at lest pull a couple of sparkplug leads to see what was happening. (I got a couple of JOLTS, of course) One and four didn't make a difference but were both sparking hot and blue. I cleaned the plugs and leaned up the pilot circuit a little and went for a ride. Runs great with no problems to report. I don't know if I've fixed anything, to be honest. I do know my bike a lot more intimately than ever, that's for sure.

After rebuilding Triumphs and Nortons for many many years, working on something well engineered like this little KZ is a bit of a revelation.

When you take something apart, fix it then put it back together, you can expect it to work. Not so with ancient English hardware.

The exercise of tracing the voltage from battery to coil terminal showed me a gradual loss of voltage and additive resistance. This will nag at the back of my mind until I do something about it, like install a relay.

I think I'll keep a set of plugs and a wrench in the toolkit.....

You guys are great.

Bill