Stupid mistake...

Been a busy couple weeks, but finally got some time to mess with her. Plugs are dry. Took a temp on the cylinders. None of the are “cold” but 4 & 6 are significantly cooler. Time to pull the carbs? 

6-131F
5-199F
4-132F
3-236F
2-190F
1-200F

I'll assume it's still running like a dog??
What did the sparkplugs look like on #4 & #6 ?? Black and sooty or .....??

The temp readings are "interesting". How did you take them? fire up the bike them once it was off   choke take the readings??

You still have the stock exhaust on the bike if I remember right so it still has the double walled down pipes. Sometimes especially with the old pipes, the inner pipe can rot away and expose the outer pipe to the raw exhaust and temp checks can be very different. Something to keep in mind and I'll assume you didn't take base readings when it was running properly so you have nothing to compare to.

If the main jets were blocked on #4 and #6, then there would be no gas to the Main circuit and also the idle circuit so the bike would end up running on 4 cylinders all the time sand $4 and #6 would show cold. 
If the idle circuit was blocked on #4 and #6 then your temp checks would show cold if taken just after warm up and if you did your temp checks when running down the road hard, would start showing up closer to the other pipes.

Diagnosing can be a bitch. Your observations tell you something is wrong so you need to "test" to hone in on the problem. What tests will you do and what results will lead you to the problem. Also, you need to know how the components all work together to make it run. 

The KZ carbs are a little tricky in their design. Fundamentally, they are 6 individual carbs with conjoined float bowls and throttle plungers.

Before I were to answer your question "Time to pull the carbs?" I would like to know more about your "Testing procedure"

Hang in there. We'll get you through it.
KB

She’s running pretty rough. The idle is bad so it’s stalling quickly, even with the choke up. I kept it reved for a couple minutes until it warmed up a bit.  Turned it off and took the temps with a laser. And you are correct. I unfortunately did not have a baseline for comparison. The plugs looked fine, no significant carbon build up. I do have the original exhaust. I looked in the pipes with a light. Of what I could see I didn’t notice any deterioration on the inside. 

Now I'm really lost. If you can't keep it running on choke something's really off. So probably time to pull the carbs. Specifically look for debris in the float bowl. The choke fuel pick up tube is the brass tube that fits in a bore in the float bowl. On the end of the pick up tube should be a brass orifice that's about .020" in diameter. if for some reason debris got into the float bowl, that orifice could be plugged and starving fuel to the choke circuit. (and why it struggles to run on choke)
 

Also, in the bottom of the float bowl there's a port that feeds gas into the bore in the float bowl that the choke fuel pick up tube goes in.
 
That's the fuel supply port to the bore that feeds the choke fuel pick up tube. On the 3 carbs I had that came with my bike, 2 of the 3 ports were blocked with crud and I had to poke them out with a drill bit. Note- there's a fuel supply control orifice in the bottom of the float bowl with as I remember it a .025" - .030"  diameter. You wouldn't see it unless you spotted it with a flashlight. (like I did.)

Then off the top of my head, as I remember it, that choke fuel pick up tube is also an emulsion tube and has small air ports in the sides of the tube, which need to be free and clear. Clearing the choke fuel pick up tube orifice requires compressed air to reverse flow from the choke plunger to blow clear that orifice. If you find ANY debris in the float bowl, Likely the idle jet (s) are plugged as well since they are smaller than the choke orifice. Bottom line- If you find debris in the float bowl, you need to understand how it got in there in the first place. Do you know the specs of the fuel filter you are using??Is it possible that something between the fuel filter and the float bowl broke free due to the fresh gas dissolving the varnish that held the debris to that part of the fuel system??These carbs as previously stated are 6 individual carbs with conjoined float bowls, but each of the 6 carbs are feeding gas to a cylinder of 220 cc's which is not much larger than a chainsaw cylinder so all of the jets, emulsion tubes orifices and air jets are really tiny compared to say a 4 barrel carb feeding a 5 liter engine.. Working on them you need to keep that in mind and realize that cleanliness is next to Godliness. Be patient. You'll get through this. and as always, we are here to help.
KB 

KB, Wow, just Wow. 
You amaze me.

dcarver220b wrote:

KB, Wow, just Wow. 
You amaze me.

Really not meant to amaze anyone. As a Chrysler mechanic back in the early 1980's, the entire Chrysler, Dodge Plymouth line up had a "Lean Burn" system which was early computerized Ignition and all the cars idled like crap. It almost became the demise of Chrysler. As a tune up mechanic, I was constantly under the gun to "fix" these rough idlers, so I had to come to understand why they had problems and figure out what to do to get them to run so the customer was happy and get the Service Manager off my back. I developed a greater understanding of the issues because if I didn't , I had to deal with a whole bunch of very unhappy people.
Chrysler used Carter 2 barrel and Thermoquad carburetors. I studied them to death and got really good at figuring them out and overcoming their short falls.
35 years later, here I am reading posts on this site over and over and over about all the issues with the Mikuni BSW32 carbs and it brought me back to my early days  with the Chrysler's. So I did what I had done before. Take them apart and study them to death, one circuit at a time.
My nuclear experience raised my understanding of what it meant to be a "mechanic" In nuclear, you can't work on a system without understanding how the system works and then "apprenticing" with a Journeyman qualified on that system. I took that understanding and applied it to my Automotive Technician Licence and realized that as a certified mechanic, I knew how to take cars apart and look for damaged parts and replace them to get the car back on the road. That attitude would never fly in nuclear, so I came to realize that most everyday mechanics are really good at "putting a band aid on a cut" but don't trust them to diagnose a "cardiovascular issue" and fix it.
I've spent countless hours studying these BSW32 carbs to better understand "how all the circuits work" in an attempt to better understand why these carbs are such a problem. If I had to guess at how many times we talk about carbs on this site, it would probably be north of 80%. And that is shameful in my mind. This site should be more about how to overcome the parts non availability, like what to do if an igniter craps out and there's non available. Or how about updating to a standalone computerized engine management system.
Scotch and I "discuss" thoughts/ ideas about the carbs and I know Scotch has spent more time studying/working on these carbs than I. I have great respect for his abilities, especially with the carbs. I try to hold off replying to these drivability issues but understand that when members post looking for help, somebody needs to jump in and offer up thought provoking answers and I guess I can be something of an air hog jumping in. I really have to work on holding off and letting others in to assist.
I could easily see a 40 page tutorial on all the circuits in these BSW32 carbs and it would be more than the average KZ1300 owner would want to understand, so we tend to just address each issue as it comes up and hopefully, what we provide is enough to fix the problem. For those that keep following along all the issues, I'm sure some of you have picked up tidbits that have raised your understanding of these carbs and will help you along the way and that's all I could hope for.
Cheers,
KB