TOPIC:

79 KZ1000 MKII
The #3 cylinder has a mind of its own. It cut out on me again today. #3 exhaust pipe is always cooler than the rest, but every now and then it totally quits. The coils, wires, caps, and plugs are good. I've always suspected the igniter, but it somewhat matches the repair manual specs. #3 will come back eventually on its own, but i'd like to be able to fix it for good. This problem dates back at least 12 years to the previous owner, but I don't even know if it's electrical. If anyone has any ideas i'd appreciate hearing them. Thanks, Elliot

Float level.

Suggest float bowl service fuel level check.
Quick easy clear plastic tube method.
You know the drill, or can find it in "search"

Too high fuel level can result in excessively rich mixture causing plug to soot and foul out very quickly.

Typical scenerio -- new plug runs great for a few blocks or a few miles, then craps out --- soot-fouled.

Okay, maybe it's electrical. But for me the culprit and cure was fuel level and float tab adjustment.

Hope it's just that simple for you.

The fuel level may be a little low if anything, but they are all the same so I didn't want to mess with them. Changing the plug doesn't always get #3 to work. It seems to come and go.

elwood wrote:

79 KZ1000 MKII
The #3 cylinder has a mind of its own. It cut out on me again today. #3 exhaust pipe is always cooler than the rest, but every now and then it totally quits. The coils, wires, caps, and plugs are good. I've always suspected the igniter, but it somewhat matches the repair manual specs. #3 will come back eventually on its own, but i'd like to be able to fix it for good. This problem dates back at least 12 years to the previous owner, but I don't even know if it's electrical. If anyone has any ideas i'd appreciate hearing them. Thanks, Elliot

Sorry I forgot you already mentioned the "plugs are good."

What are compression readings, and are valve clearances to specs?

I'll work on checking compression and valve clearance, but that won't be as easy for me to check. Thanks again.

Compression is an easy check, and usually done with cold or fairly cool engine (wide open throttle, please).

But marginally too tight valve closing may allow compression to read okay when cool, but allow valve to start leaking as engine temp increases.

Expansion of metal parts due to increasing temperature is reason for allowing the specified valve clearance when cold.

So it's important to also check the valve clearances, even though cold compression figures may read okay.

And, yes, checking the valve clearances involves removing the valve covers, whereas checking the compression only requires removing the spark plugs.

But it's pretty easy to check the valve clearances -- whereas changing the shims to adjust them requires additional effort.

Good luck with finding a cure for this long standing problem.

The thing that gets me is that I don't have to do anything and #3 will come back on its own eventually. Usually when I least expect it, and I just hope I'm holding on at the time.

I just had the same problem with my #4 cylinder. When I finally got to where I had to remove the carbs after all of the other checks, and pulling my hair out, I found out that the PO somehow had smashed the end of the carb holder to where the carb outlet wasn't even inside the carb holder, and it was intermittantly leaking air. I just couldn't see that until I had the carbs out.

If it was the igniter, I would be having trouble with more than just #3, right? At least 2 and 3 would be affected. A main fuse blew today. That's the first time in 10 years. It wasn't the filament that blew. The filament is still intact, but it completely melted through the bottom of the metal end cap. Weird.

I had a tight valve and only registered 45 compression. Checked valve clearances, and found the tight one. Set it to within specs, and got great compression. I'd recommend to start there.

elwood wrote:

79 KZ1000 MKII
The #3 cylinder has a mind of its own. It cut out on me again today. #3 exhaust pipe is always cooler than the rest, but every now and then it totally quits. The coils, wires, caps, and plugs are good. I've always suspected the igniter, but it somewhat matches the repair manual specs. #3 will come back eventually on its own, but i'd like to be able to fix it for good. This problem dates back at least 12 years to the previous owner, but I don't even know if it's electrical. If anyone has any ideas i'd appreciate hearing them. Thanks, Elliot

If valve clearances are okay, might try swapping coils to see if #3 cyl problem moves to #4 which would suggest an ignition issue.