Choke Enrichment not working.

1978 kz1000 Ltd. I recently rebuilt a set of 28mm with accelerator pump, from a 1980 vintage kz1000 Ltd. Installed them with new manifolds and also the air correctors that Zed1015 offers. Everything was working great. Bike has never run this well. My problem is the last few starts the choke has no effect. It is needed to start the bike, but once started regardless of choke lever position there is no change in rpm. Up down or middle, nothing, almost like the physical connection between the choke lever and the plungers has come uncoupled. I’ve had to sit on the bike and twist the throttle open and hold it to allow the bike to warm up... once it’s run a minute or so everything is normal. It idles well at 1K. It’s running so well This has completely baffled me. How can a mechanical system that worked for the first 3 months just stop functioning. Just so I’m investigating the proper circuit I’ve identified what I think is the enrichment parts in the attached photos. Please confirm I’m in the correct ballpark. If anyone has suggestions I greatly appreciate any and all advice.

You might want to check the O rings on the plungers situated under the brass nut arrowed.. If they are not sealing the choke does bugger all. Be surprised if all four went simultaneously though.
I assume the lever is lifting the plungers. I have heard cases where the lever to shaft joint arrowed has become loose and the lever just swivels on the shaft and doesn't moved the plungers wherever the lever is.
Just had another look at your pictures. You lever is in the off position but your plungers appear to be fully open. The shaft has a V cut into it which runs along the back edge. Each Lifter fork has a crosshead screw with a point on it which should lock the lifter fork to the shaft. If you inadverlently forgot to tighten those then again the lever would do bugger all except turn the shaft but not the lifter forks. Doesn't explain why your plungers appear to be stuck open though. On all my VM carburated bikes the bottom of the white collar sit on top of the black rubber seal when the choke is off and the lifter forks are on the bottom of the white collar.. On yours you can see a good 5 or 10mm of the brass plunger rod and the lifter forks are at the top of the collar.
I suspect something is assembled incorrectly.

As Warren has spotted it appears the plungers are not fully closed.
If this is the case there may be something under one of them holding them open.
Maybe a piece of plunger seat that has disintegrated and fell out.

zed1015 wrote: As Warren has spotted it appears the plungers are not fully closed.
If this is the case there may be something under one of them holding them open.
Maybe a piece of plunger seat that has disintegrated and fell out.

Its the forks position I cant understand though. If the lever is level then the forks should be pushing the plungers down by the bottom of the collar but they are still at the top in the lft position.
My suspision is a loose joint between lever and bar and the lever has partially twisted on the bar so when you operate the lever its no longer turning the bar.

Warren3200gt wrote:

zed1015 wrote: As Warren has spotted it appears the plungers are not fully closed.
If this is the case there may be something under one of them holding them open.
Maybe a piece of plunger seat that has disintegrated and fell out.

Its the forks position I cant understand though. If the lever is level then the forks should be pushing the plungers down by the bottom of the collar but they are still at the top in the lft position.
My suspision is a loose joint between lever and bar and the lever has partially twisted on the bar so when you operate the lever its no longer turning the bar.

Yes! Enlarging the pic shows a gap between the bottom of the collar and circlip so they are not fully pushed down.
As you say possibly the lever is loose on the shaft and lifting it barely fully lifts or closes the plungers.

Thanks Warren3200gt. I'll double check the lever to rod connection and the cross head set screws. I’m almost 100% sure I did it correctly when rebuilding the carbs. I remember playing with the plunger lifting forks to get them positioned correctly to get smooth full open and closed travel while they were on the bench. I replaced the plunger O-Rings, I used Keyster kits for parts but reused the factory plungers. I firmly remember matching up O-Ring sizes with original to make sure I used the float bowl O-Ring on the float bowl screw, they were very similar in size to the choke plunger O-Rings. The Keyster plunger are a different design without the pin/needle on the bottom of the plunger. I know I installed new plunge spools and dust caps. So with that much attention to the choke circuit during rebuild I’m hesitant to say I missed something. I had to source one new plunger because one on the carb rack was bent. Must of had something fall against the #4 carb long before I purchased them.

If the lever to rod connection failed it has done so after rebuild. More pictures of the inspection and cleaning process.


All this is hypothetical till I can get home and actually put my hands on the bike

I zoom in and see the fork resting on the bottom lip of the spool and see clearance between the top of the spool and the e clip.

The plunger spring should be closing that gap. Whatever the issue is those plungers should be with the bottom of the spool touching the dust cover with the lever in the closed position. If the forks werent there would the plungers spring to the closed position?
Without the forks on you should be able to lift the plunger with your fingers, let go and they snap shut. If they dont do this it is possibly your issue.

Waren3200gt, thanks I will check the range of motion on the plungers this afternoon. My counter to your assessment is, why then does the bike run better than ever if the choke plungers are not fully seated. And how dose that condition explain the lose of the choke functionality

Im not sure is the truth. However what I am sure of is those plungers are not seating correctly. The reason for that could be they are sticking, the lever and rod connection is suspect or a zed1015 said there is a piece of crap under one of them. Or it could be something else entirely. All I can say is what I see from the pictures you have posted. It may even mean that once you have resolved the choke issue you may find that you need to retune your carbs.
First thing you need to check is that the lever actually lifts all the plungers and that they will all close fully.

Wow. If there is better performance in the future of this bike then I’m really excited. It flat out impress’s me. Mind you it’s been 35 years sense I rode my big bore 900. Maybe I just don’t remember. That KZ900 had andrews cams, 1105 bore. 29 smooth bores dyna S and a 14 tooth primary. It was a rocket. My current bike is not in the same class but very impressive in itself.