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My buddies and I have been working on restoring a 1980 KZ550. We have been tinkering with it for a year now and have put it through two riding seasons. Getting ready to head to the Smokies in May to ride the "Tail of the Dragon" and want to take this bike along.

Right now cylinders 1 & 3 are not firing. So far we have done everything we can think of and are just out of ideas. Here is what has went down so far:

1. Bike was running on all fours and just randomly stopped firing on two, as mentioned above.

2. Prior to bike only firing on two cylinders, we did pull and completely rebuild the carbs. We also had them synced by a mechanic, so we know all is well there.

3. We have also rebuilt the petcock, cleaned and coated the gas tank so we know it's rust free

4. Replaced points and condenser as well as plugs

Tested plugs and get spark on all four, but still only two cylinders firing. Looks like cylinders 1 & 3 are dry, figured they'd be wet if fuel was at least getting to them but not igniting, yet, there is fuel in the bowls of the carbs so I guess I can assume (since carbs were just rebuilt) carbs are not the problem. Have not yet replaced the coils, but figured they were still good since spark was getting to all four cylinders.

Pulled the cam covers off thinking maybe the cams on 1 & 3 may have rounded off a bit and were causing trouble. But, to our surprise, the cams were in great condition, timing chain as well. So guessing we can rule that out.

Stumped on this one? Anyone got ideas? Is there something special about 1 & 3 and 2 & 4 pairs that may lead to a diagnosis? I thought the firing pattern was 1 & 4 and 2 & 3, with 1 & 4 being fired off one coil and 2 & 3 being fired off the other...which is why I am stumped. Why would either coil only be firing one of the two cylinders that it operates?

HELP! Been working on this for 6 hrs now with no luck.

- Mike

email: [email protected]
 

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Sparkplug caps can fail too. They unscrew from the plug wires. Z1 Enterprises, Inc. - Specializing in Vintage Japanese Motorcycle Parts sells new ones. To check for spark, put a known good sparkplug in a cap, lay it against the head and turn the engine over. If the cap is good, you will see/hear a snap when the plug fires. If no spark,further inspection is needed.

I'd do this: remove the gas tank,make a digram of where the primary(small wires) go on the ignition coils and using a multimeter set on OHMS, check the ohm rating of the coil(s). They should read between1.8 to 3.3 OHMS.

Have you checked the coils output ports? Pull the plug wires, and using the multimeter set on OHMS, check between the two ports(where the sparkplug wires go) they should read between 10.4 to 15.6 K OHMS.
 

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Yeah, would still swap the coils to make sure that the symptoms did not move with it.

Then I would go back to the carbs unfortunately.
 

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Never "assume" something is OK just because it was fixed already. Anything thats been fixed can still fail again. The plugs are dry so I'd say the valves aren't opening (but you've checked that you say) or gas isn't flowing through the carbs. Could have been some trash or water that made it's way to the carbs after the cleaning/rebuild so thats the first place I'd look. I've seen plugs that would spark when you look at/check them but fail to make the spark under compression. But then that doesn't go along with the dry plugs you describe.

Since it's failing on one cyl off each coil I don't think there's anything to gain by swaping the current coils with each other because they both exhibit the same problem if it's a coil problem.
 

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No mike, he did not say he checked the valves. He said he checked to see if the cams were wore down.

How do you know that 1 and 3 are not firing besides they being dry? That is no indication. You should check compression and valve clearances before you do anything else.
 

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I had an intermittent firing problem on #1 & #2. Everyting was checked & set as per the manual (carbs, ignition, new plugs, etc) & I had spark on all four plugs, but still had the same intermittent problem. Finally, simply redoing all of the spark plug wire connections solved it. The connections become poor over time from oxidation, and the presence of spark does not indicate good spark. Not sure about your bike, but the plug wires unscrew from the coils on my 81 650.
Good point herk. My daughter's car was running poorly and her boyfriend thought it might be the pcv valve. After some checking we found out it was missing on number 2. So we do some swapping around of the plug wires to check the wires and coils. We did not find much difference between them but when we were done swapping around the car had stopped missing. The only thing I could conclude is there was a bad connection due to corrosion which was remedied by our unplugging and replugging of various wires. My wife is telling everyone that I fixed it but I did nothing but help him check. :mrgreen:
 

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No mike, he did not say he checked the valves. He said he checked to see if the cams were wore down.
If the lobes are good then the only option a valve has to NOT open is to break the camshaft or chain/sprockets. Since he looked at the cams I'm pretty sure he would have noticed any of those problems so thus my statement that "he's checked that". :biggrin:
 

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What I was saying...er trying to say anyway...was he could have valve float from lack of clearance. Thus he did not say he checked the valve [clearances] is what I was driving at. And without compression in those holes the plug should not be wet.
 

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Check the plug wires are on the right plugs.

One coil fires 1 & 4, the other 2 & 3.

If you want to confirm spark, pull the spark plugs out of the head and put them in the plug caps - ground each of them on the cylinder head and with the ignition on, turn the engine over with a wrench on the end of the crank. When the each piston comes to the top of the bore, the plug should spark.
 

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Yea sound like you got abad coil. I had the same prolem with my '79 kz1000 and as soon as I replaced the coils it was all good. I sugest that you replace both coils at the sam time since your going to have the tank off and if one failed it's time to replace them both.
 

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The ignition coils on these older bikes have dual ports(where the sparkplug wires go) it makes no difference which port you use, just make sure(at least on my bike) the left coil goes to # 1 and # 4 and the right coil goes to # 2 and # 3.

Some 550's,650's and possibly 750's have it wired backwards to what I said with the right coil to # 1 and # 4 and the left coil to # 2 and # 3.

The way I determine the wiring on the primary side(smalll wires) is to consult the shop manual and then check the firing sequence(again in the shop manual).

I'm not sure why Kawasaki did not make uniform the coil wiring in all it's motorcycles.
 
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