81 kz550 dead on 2 cylinders

Hey everyone
I was riding to work today on my kz550. I stopped at a light after riding for about 15 minutes and the engine shut off. When i touched the headers both cylinders 2 and 3 are cold and 1 and 4 are hot. They are attached to different coils so i ruled that problem out. What else should i be looking at so I dont have to tow it home?

If 2 & 3 are attached to different coils you have them hooked up wrong. Ed

nickleo373 wrote: Hey everyone
I was riding to work today on my kz550. I stopped at a light after riding for about 15 minutes and the engine shut off. When i touched the headers both cylinders 2 and 3 are cold and 1 and 4 are hot. They are attached to different coils so i ruled that problem out. What else should i be looking at so I dont have to tow it home?

Where 2 and 3 were cold right after engine shut off, the engine had likely been performing with combustion happening in just the two outside cylinders 1 and 4 .

Numerous possibilities, but here are some random thoughts.

Out of gas?

Is any black goo oozing from the ignition coils?

Loose spark plugs?

Valve clearances within spec?

Good Fortune!

Sorry i must have mixed up the coil wires when looking at it. They are hooked up correctly. The bike was running good until i had it stopped fo a couple seconds. It just shut off. It didnt sputter or anything. The tank is full, valves just adjusted a couple months ago. I'll have to take the tank off in a little while to look at the coils and wires

You were riding for 15 full minutes on 2 cylinders and didn't notice a foul running engine? If 2 pipes were cold to the touch after riding that far, then they weren't firing at all and odd you got that far without noticing a problem and stop to investigate. As Patton said it cld be one or a combination of several possibilities, starting with the 2/3 coil wld be best place to start. Good luck. ......................................Mike

Vroom-vroom!!!.

Perhaps the over-worked two outside cylinders 1 and 4 simply over-heated, and will run after allowing to cool.

But of course won't resolve the 2/3 non-combust issue.

Perhaps #2 and/or #3 spark plug has fouled out?

Is a tool kit available for removing #2 and #3 spark plugs to watch for sparks on them while spinning over the engine?

Perhaps installation of new plugs in 2/3 would enable combustion long enough to ride home (for example if too high fuel level was causing a plug to load up until it eventually quit firing).

Good Fortune!

I ended up towing it home from work because I wasn't able to figure it out in the parking lot. There is no spark on cylinder 2 and 3. I made sure the connections at the coil were tight and it didn't make a difference. Is there a way to test the coil itself?

When you check for spark, make sure both plug wires have a way to spark. They must make a complete path to each other, be it through the engine, or some other piece of metal. Failing to do this will damage the coil or igniter eventually.

So check for spark on all plugs. You can do that several ways. The easiest is to take the plug wires off of the plugs in the engine, and put spare plugs into both plug wires and lay them on the engine so you can see if they spark.

For the 1-4 coil, use a screwdriver to tap on the center of the pickup with the black and blue wires going to it. The plugs on the 1-4 coil should both spark.

For the 2-3 coil, use a screwdriver to tap on the center of the pickup with the red and yellow wires going to it. The plugs on the 2-3 coil should both spark.

If the 2-3 fails to spark, remove the skinny black wire on the 1-4 coil and put it in place of the skinny green wire on the 2-3 coil. Then try the tap test again on the black-blue pickup. If 2-3 sparks, then the igniter or red-yellow pickup is bad, and the 2-3 coil is good.
You can put the skinny green wire onto the 1-4 coil, and try to tap the red-yellow pickup. If 1-4 sparks, then the igniter and red-yellow pickup are good, and the 2-3 coil is likely bad.

Switch the electrical wires between the two coils to see what happens to the spark. That will tell you if the problem is the coil or the ignitor/signal generator.

Alright so in a strange turn of events, I switched both ignition coils from one side to the other and now every cylinder is sparking and the engine is running like normal. The round ground connector on the 2 and 3 ignition coil was a little bit loose but I'm not sure that'd cause this problem. I let it idle for a few minutes and everything seemed to be back to normal. Is it possible that a coil or igniter would fail after a little bit of riding and not fail right away?

Yes. Sometimes when a coil I going bad, it works ok until it gets hot and then suddenly dies.

It's been a couple weeks since I've had problems with the bike but yesterday I turned it on and let it warm up in the driveway. About 2 or 3 minutes after starting it, the bike shut off just like it did the day I had it towed. The coils have been switched to different cylinders but cylinders 2 and 3 are still the ones that are not firing. Does this narrow the problem down to the ignitor?