KZ550 carb issue?

I recently found an 82 kz550, dirt cheap, but it's only running on 2 cylinders. A quick check revealed that I didn't have any spark in cylinders 2 and 4. A swap of the plug wires resolved that issue, but it's still not firing on those cylinders. I'm new to motorcycle repair an maintenance. Is this likely a carb issue, and what would you all recommend as a first course of action?

Thanks in advance!
CVM

Would recommend new spark plugs first, if there is any doubt about the old ones. If you have spark on all four cylinders that is good! Personally use NGK D8EA in my KZ550. Be advised that I had a misfire on two of my cylinders recently and ended up replacing both coils and that resolved that issue. Also consider replacing the spark plug caps. They are reasonably priced from Z1 Enterprises. Then you can consider possible carburetor issues from there. If you have the TK-22 carburetors, they are relatively easy to work on. KZrider member Loudhvx is very knowledgeable and helpful on these carburetors.

Here are the plugs. Like I said, they're all firing now. I have a set of coils I can use from my parts bike, but if I'm getting spark on all four when they're grounded to the block, I assume the coils are good. I'd like to see a bigger spark, I guess, but there is definitely spark there.

As you can see, #2 is clean and wet, and #4 has indeed been firing at some point, but not right now. I think I'm going to swap the plugs around and see if the problem moves with the plugs.

The thing about coils is that they can work intermittently, especially if those are the original 29 year old units. Mine tested fine with an ohmeter, but failed in actual service. Would still put in new plugs and consider new spark plug caps and go from there.

Here are the plug caps that I recommend from Z1 Enterprises.

NGK spark plug caps

Cool, thanks! I'll try a local cycle shop tomorrow, but if they're more than $5 apiece there, I'll go with Z1.

If you get the NGK spark plug caps, the ones that say LDO5F are what is called for on our KZ550's.

Another tidbit for you, when/if you replace the spark plug caps, the ignition wires are solid core. When you unscrew the old caps, you will see the wire and it doesn't hurt anything to cut off a little bit of the old ignition wire so you can see a fresh inner core wire. Then just push and screw the new cap on. I apply a little dishwater soap on the new rubber part that goes on the wire so it will slide on easier.

As GPZ550 said, make sure it's not ignition before messing with carbs.

Just to confirm, you have one coil firing cylinders 1 and 4, and the other one firing 2 and 3, correct?

If that's the case, then there are other tests you can do to verify the ignition by swapping parts around.

First is to swap both coils. To do this swap the wires from one coil to the other. That means plug wires 2 and 3 with plug wires 1 and 4, AND the small black wire with the small green wire at the coils.

If the problems move, then the coils are bad.

If the same cylinders have the same problems, then it can be the plugs, plug wires, igniter or pickups. Similar swaps can be done to check those as well.

When you are eventually done verifying ignition, I have tk-22 info here .

Thanks!
I work tomorrow, so no motorcycle work, but now I've got more stuff to try on tuesday.

Even with properly timed adequate spark and perfect carbs with ample good fuel supply, combustion failure within a cylinder may result from inadequate compression due to whatever reason.

If not already done, would perform a compression test on every cylinder, and assure all valve clearances are within specs.

A leak-down test could be helpful toward pin-pointing the source of any compression loss.

Good Fortune!