TOPIC:

I would love to hear any ideas on how to replace the small rubber pad at the bottom of the brass fuel enrichment plunger .
Thank you Greg

I would get some sheet nitrile or viton rubber & use leather hole punches that makes hollow holes.

I’ve thought about this also. Have you tried to get the old one out yet. The heavy roll on the end might make it difficult to reinstall without damaging the rubber

No eBay APP ID and/or Cert ID defined in Kunena configurationA member here, "zed1015". He is in Great Britain. He is a very knowledgeable, Z1 Dragracer, Restorer, Machinist. He is the one who makes the air corrector jets, that have been seen and sold on here. I have bought a set.
He sells on ebay with the same nickname. He has developed the process of making the rubber out of Viton material and rebuilding these choke plungers. He also has a new old stock set for big $$.
Or you can just buy old carb parts of off ebay, and hope they are better than yours. What I do with the old carb choke plunger part is to soak with wintergreen oil. Then keep them in a plastic bag with silicone grease smeared over them till I need them. It rejuvenates the rubber!
Here is a link to ebay for his parts:

Yes! I have been offering a plunger re-seating service here in the UK using modern fuel resistant Viton.
It was mainly for the early obsolete plungers on the SC carbs but will do the late 24/26/28 SS as these are also obsolete as a genuine item and pattern ones are scarce with the Keyster ones only available in the big rebuild kit and they don't have the brass needle attached which isn't good.
It's £50 per set + post but I haven't advertised overseas or on the forum because of the two way shipping .
It's a tricky process as the original seats were installed and the brass edge rolled over to secure them.
With the tooling and jigs I made I can fit the same size pad without disturbing the rolled edge so that the seats are held captive as original and not just undersized and pushed in the hole.
The ones on Ebay are Genuine as new NOS Mikuni which are rare and come with new Mikuni dust caps and the price is comparable to the last pattern ones I saw but to account for the selling fees and taxes i've had to add 20% on top.
Out of Ebay I want £100 for them which is what they cost me.

What's the purpose of that rubber part anyway? I've rebuilt dozens of sets of VM's and never found the need.

Nessism wrote: What's the purpose of that rubber part anyway? I've rebuilt dozens of sets of VM's and never found the need.

The rubber seal shuts off the enrichened fuel supply when not needed for cold starts.
If the seal is not doing its job it can be the overlooked cause of unsolvable rich running issues , idle creep and lower MPG etc.
Much like running with the choke partially on.
It's becoming more of a noticeable issue now that they are getting over 40 years old and also degraded by ethanol rich fuels.

>>> "The rubber seal shuts off the enrichened fuel supply when not needed for cold starts.
If the seal is not doing its job it can be the overlooked cause of unsolvable rich running issues , idle creep and lower MPG etc.
Much like running with the choke partially on.
It's becoming more of a noticeable issue now that they are getting over 40 years old and also degraded by ethanol rich fuels. "

Yep, if the seal leaks the bike runs rich.

I've tried the Keyster choke valves (with the flat bottom) but gave up on them. Carbs seemed to be unstable at idle. Why do they not work as well as the originals with the point on the bottom?

Do the Keyster parts have the rubber seal?

TexasKZ wrote: Do the Keyster parts have the rubber seal?

The Keyster ones do have a rubber seal but they don't have the brass needle so don't have the sensitivity of the originals.
The brass needle acts like a jet needle but a bit cruder and allows the fuel to be feathered in.
The ones without are more all or nothing in operation.

Keyster vs KHI