Kz1000ltd running rich? Help needed

I’ve been restoring a 1981 Kz1000ltd for the last couple of years. You can see the entire story here if you look for “piston hole” in the engine section.

Carbs have been cleaned thoroughly several times on an ultrasonic machine and carb cleaner, compressed air, etc, and all o rings and float valves are new (keyster). Carbs are synced and have standard 122,5’ jets. Float level has been set with tube clear and is set to standard height (measuring float height would make carbs overflow). Pilot jets are at 2,5 turns.
Intake boots are new and Kawasaki original, and have been installed with some sealant, to avoid vacuum leaks. Brake cleaning fluid sprayed on boots makes no effect on engine running.
Valves have been adjusted. Plugs are Ngk B8ES

Bike behavior:
- starts really easy, almost at first touch of starter button (with choke) from cold 
​​​​​​- keeps a steady and healthy idle
- Runs great, clean acceleration, good low end power and a certain “kick” around 3krpm

but…
- starts running a bit rough after heating up
- rpms (when hot only) return slowly to idle, with a little bump on 2k rpm (see video)
- feels like it loses a bit of power
- once warm, it will not start if you don’t give it some throttle 
- plugs are quite black and sooty





I have what I think is an overly rich condition, but I thought I would solve it with getting the right fuel level, and doesn’t seem to have solved anything.

Suggestions? Thank you in advance, and have a happy new year all!

Have you had the choke plungers seals repaired ?

 

No, Zed, I have not. 

I’ve read a lot of your posts about it. Would these symptoms be compatible with damaged choke plungers?

cartal wrote:

No, Zed, I have not. 

I’ve read a lot of your posts about it. Would these symptoms be compatible with damaged choke plungers?

Yes!
The 'Choke' is an enrichener and when the rubber seals are worn or hardened etc the seals do not fully close off the fuel supply from the float bowl.
The choke effectively remains on which causes rich running that has an increasingly negative affect as the engine warms up..
Symptoms are sooty plugs, rough running, power loss, reduced mpg etc.
 

It must be that, then, as I cannot find any other reason.

Please tell me what your preferred approach to sending the plungers to you is.

thank you!

cartal wrote:

It must be that, then, as I cannot find any other reason.

Please tell me what your preferred approach to sending the plungers to you is.

thank you!

As there seems to be no forum messaging system please email me at     zed.1015@yahoo.co.uk     and i'll provide all the details of where to send etc.
Thanks.

Sent. Thank you!

Actually, I just took the plugs out. These are brand new b8es plugs, with less than a hour firing.



in order, 1 to 4 from left to right.

cyl 4 is starting to look better, but still 1 and 2 look horrible.

Additional question: these spark plugs are brand new. Can they be cleaned and reused?

For Your consideration Cartal. These BS34's by design can be prone to "over fueling choke" issues. They don't utilize a conventional spring to push the plunger back down, Suzuki did. You'll note the accordion bellows on your set. They instead use the choke rod lifters with springs on the rod inside the lifters and a circlip to index them. The fork in the lifter piece pushes down on the plunger. You Have to set-up this choke rod and bits correctly!! Note in picture of what Your set is and what a BS34 Suzuki loose plunger look like. Just something to think-about and double check..   

That engine doesn't sound right.  Are you sure it's running on all four cylinders?

You might want to start it up from cold, and after it just starts to warm up, very carefully touch each header pipe to see if they are all warming equally.  Needless to say, be very careful.  Gotta work fast.

The symptoms are sort of conflicted here; rich running, but a slightly hanging idle (which suggests lean).

You might want to check your plug caps for resistance.  Snip off 1/4" of the end of the spark plug lead also, for a fresh electrical contact.  

Thank you Ed. It is. I checked again yesterday with an infrared thermometer and all 4 headers get hot.

If I go back to the restoration moment when I did the carbs, something got a little overlooked, as I focused on my broken carb, rather than on absolute certainty.

First, the main jets (which I believe control Wot, so should not be the problem here). I run 122,5, but some phony plastic jets, rather than brass (bike came with them). I don’t know if these are good but maybe I should try some brass. I have some 120 available.

second, the needle, and this is important, as controls mostly part throttle. Bike came with needles on the second notch from the top, and I moved all to notch #4, essentially making the bike a lot richer.

I think I should try to get those needles back to #2, and see from there.

Ed, ignition cables are new, as are spark plug caps