Intermittent engine fault

New to the forum and still navigating around. If this is the right place to ask, I would like to seek advice as to where to look for the fault I have on my '80 KZ550. It is stock aside from the solid state ignition from the next year.
Mostly my bike runs like a dream. I had the top end off to replace cam chain rubbing blocks and a re-seal about two months ago. Everything was much better. Then an intermittent miss started happening. It seems to drop to two cylinders suddenly but usually will run OK at near full throttle when this happens. It usually goes back to running like before all by itself after a short while. Frustrating. If I could get it to just quit, I could find it....
It mostly happens after the bike has been ridden, stopped and re-started.
I have gone through a number of things to find the fault. I rebuilt the petcock. I went through all the ignition wiring cleaning and applying dielectric grease to all terminals. I thought I found the fault yesterday when I found a spark-plug lead up against the head that looked like it was arcing.
I consider this a life-threatening type of fault. I could get nailed if this happens when I'm trying to cross a busy intersection...
BTW I have removed the whatchallit clean air system and blocked all holes, oh and unblocked the idle screws and enrichened them up a tad. (long time ago)
Bill

If the coils are original, I would punt them into the can and get new coils from Z1 Enterprises. Intermittent missing after warmup is a classic failure mode of an old coil.

Thanks for the reply. I already had one coil just quit over a year ago and replaced it with a used one from Ebay.

I did use the search function and it works much better than other forums. Nice.

I was considering replacing the coils and now I think I will sooner rather than later. I have the coils spec'd for EI but they were used when I bought them.

Big help and big thanks,
Bill

Never mind. I called Dynatek and got the part numbers. Thanks.


[strike]I just searched the Z1 site and found these.
www.z1enterprises.com/Dyna-Dual-Output-2...-pair-DC41-1306.aspx
Would these be the correct coils for solid state ingition? Thanks in advance.
BTW my coils are 2.7 ohms.[/strike]
Bill

alot of people just run the 3.0 ohm green dynas. some people runs accels also.

I would still be leery of the spark plug wires and caps. If you saw arcing be before when the wire was close to the head, then they are leaking and I would replace them as well. If the spark plug caps are the are the screw in type, you may want as a quick trial, to cut off some of the end of the wire (less than 1/2 depending how much slack you have) and reinstall the cap onto the wire. This may solve your problem without need a new coil. Easy enough to try. Just say'n. I had leak wires once. And the bike would stutter, especially when you crack the whip on it. Good luck.

Joe

My 80 750 would do something very similar. Ride for a bit, then it would drop 2 cylinders. At very low RPM's it would be ok, but anything more it would cut out. I could still coax the RPM's up, but the bike had nothing for power. I replaced one coil with another original one. That lasted for maybe 4 weeks, and wouldn't you know it, the other coil went to a better place. Apparently the coils just couldn't live without each other after 28 yrs. I replaced them with the grey 2.2 ohm dyna's and haven't had any issues since, except I had to make some makeshift mounting brackets using some steel angle brackets from a local hardware store. When I sold my 750 I put my 550's coils on it and put the dynas on my 550. The mounting brackets on my 550 frame were much better orientated and they bolted right up. Not sure if the coil mounts on the 550 changed from 80 to 82...

KBillZ wrote: Thanks for the reply. I already had one coil just quit over a year ago and replaced it with a used one from Ebay.

Me too. The "good used one" I got lasted about three months before it failed. Coils don't age well.... :ohmy:

The place where the ignition coils mount is not a good one for cooling, as it traps the engine heat. Add years of this heat, along with the occasional stop and go traffic on a hot day, and the coils have had their life baked out of them.

Gray Dynas are what you want for the factory electronic ignition, as Apbling said.

30 year-old coils are a stranding-waiting-to-happen.

If you can determine which cylinders are dropping out, you can swap parts until you positively identifyt the bad part. But starting with new coils will put you ahead of the game.

I've had nothing but bad experiences with dieletric grease on terminals when I am troubleshooting someone else's bike. Usually I end up replacing all of the connectors that had the grease put on them, before all of the gremlins go away.

There is a lot of info in my signture for 550's. Especially read te warning about the valve train and the valve cover.

Thanks everyone.
I ordered new coils from Z1 and I think I'll ride my other bikes until they get here. I def don't want to get stranded. I think I'm due though. 40 years since I had a bike in the back of a pick-up. Knock on wood!
I ordered wires to go along with them since I'm pretty sure that 32 years is a good long life for plug wires, too.

BTW just a bit of history. I bought an '80 KZ550 new back then and I loved it. Then I went to the bike show and they had the GPZ550 there. With black chrome exhaust and handlebars, Please give me a ticket bright RED, I was a goner. I still remember the new bike smell....
I got one of the first 10 GPZ550's in the country. The other 9 went to a road race school.
Years later when I was thinking of getting a daily rider I mused over the Kawasakis and quite frankly I found the KZ to be a better day to day bike. I still have a bit of lust over that GPZ, though.

My bike has all the '81 upgrades like EI, taller gearing, taper roller steering bearings and so on.

Thanks again.
Bill

1980 KZ550 with '81 EI
I got my coils and installed them. It's been raining alot so I just sneaked in there between showers and took 'er for a spin.
No good. Still does it just exactly like before.
It really 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