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You win a few, and lose a few... 18 Aug 2022 16:30 #872448

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I'm glad to hear that there's some interest in a thread about carbs.  I'll start one this weekend with details of the two sets I've got currently.

Preview...

Set one: Gang bracket across the top, silver anodized slides, pilot fuel screw, O-rings on the needle jets, two different brackets managing throttle stop and cable holder, brass choke plungers

Set two: Gang bracket across top, gold anodized slides, silver colored pilot air screws (made of zinc?), choke plungers silver colored (material?), two different brackets managing throttle stop and cable holder.  Choke lever has plastic/rubber end.
Ed

Carburetor O-ring Kits For Sale: Mikuni VM & BS/CV, and Keihin CV34 (as used on KZ750E/H/N/Spectre, 400)

www.kzrider.com/forum/forum-index/faq-wi...owner-things-to-know

1981 KZ750E2
www.kzrider.com/forum/11-projects/604901...z750e-project-thread

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You win a few, and lose a few... 18 Aug 2022 20:22 #872453

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Consistent with the title of this thread...

I'm cleaning up parts in anticipation of finishing set #2, when noticing the throttle cable bracket has a chunk broke out of it.  The cable won't stay seated with the chunk missing.  My two sets of parts carbs have a similar bracket, but not the same.  Damn.  Searching ebay turned up one, though.  Thank goodness.  My "good deal" core set just took a dump, but at least I found the part needed.



 
Ed

Carburetor O-ring Kits For Sale: Mikuni VM & BS/CV, and Keihin CV34 (as used on KZ750E/H/N/Spectre, 400)

www.kzrider.com/forum/forum-index/faq-wi...owner-things-to-know

1981 KZ750E2
www.kzrider.com/forum/11-projects/604901...z750e-project-thread
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You win a few, and lose a few... 18 Aug 2022 23:04 #872457

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, choke plungers silver colored (material?), 

All plungers are brass.
Silver ones are thin plated, Pretty sure it's chrome but they are prone to wear and flaking . 
Later ones plain brass.
All the VM/SS ones with the same lifter end are interchangable throughout vm22 to vm28.. 
 

AIR CORRECTOR JETS FOR VM CARBS AND ETHANOL RESISTANT VITON CHOKE PLUNGER SEAL REPLACMENT FOR ALL MIKUNI CARBURETTORS
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You win a few, and lose a few... 19 Aug 2022 05:47 #872466

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I’m looking forward to seeing set 2 that has been described as different, possibly an earlier set
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
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You win a few, and lose a few... 23 Aug 2022 11:08 #872701

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Early VM26 has what looks like teflon liners inside the throttle shaft grommets.  Unfortunately, every set of these grommets I've come across have had the liners coming loose.

Also, before and after bead blasting. 


 

 
Ed

Carburetor O-ring Kits For Sale: Mikuni VM & BS/CV, and Keihin CV34 (as used on KZ750E/H/N/Spectre, 400)

www.kzrider.com/forum/forum-index/faq-wi...owner-things-to-know

1981 KZ750E2
www.kzrider.com/forum/11-projects/604901...z750e-project-thread
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You win a few, and lose a few... 24 Aug 2022 16:04 #872782

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So, the donut seals shown above were made from 1/16" (0.0625") Viton sheet.  For my latest rebuild project, I was going to do the same thing, but realized the old seals are 2mm (.080") thick.  Looking on the internet, and it seems that the UK is the easiest way to get some 2mm sheet stock.  Guess the project will be on hold until I figure this out...
Ed

Carburetor O-ring Kits For Sale: Mikuni VM & BS/CV, and Keihin CV34 (as used on KZ750E/H/N/Spectre, 400)

www.kzrider.com/forum/forum-index/faq-wi...owner-things-to-know

1981 KZ750E2
www.kzrider.com/forum/11-projects/604901...z750e-project-thread

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You win a few, and lose a few... 25 Aug 2022 02:26 #872809

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You will find that the extra 0.4mm of the VM'S correct 2mm thick 75 shore grade B or F viton that must be used for fuel and indent resistance longevity makes a marked difference to the difficulty of install which makes it almost impossible manually by hand without damaging the brass securing edge.
This is why i spent weeks developing and continue to improve and modify the encapsulated insertion jigs,mandrels and peripheral tooling to enable repeatable results without risk of damage. 
Even then many insertions are not successfull on the first attempt and due to the varying swage patterns and orifice sizes that result from the original manufacturing process further steps have to be employed to ensure correct install both mechanically and visually .
The earlier chromed plungers are particularly awkward with the later plain brass less so..
 

AIR CORRECTOR JETS FOR VM CARBS AND ETHANOL RESISTANT VITON CHOKE PLUNGER SEAL REPLACMENT FOR ALL MIKUNI CARBURETTORS
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You win a few, and lose a few... 25 Aug 2022 06:50 #872818

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Hey Zed,
while I DO appreciate your zeal in terms of making your choke plunger rebuilds as good as possible, I'm a little unsure how much details like the grade of Viton matter.  Mikuni used Nitrile for sealing, which works wonderfully because the slight swelling with gas contact affords a good seal.  Could the indent seen on the choke plungers actually be swelling around the seating surface?
Have you ever taken apart some carbs to see if your viton seals are indenting over time?  Regarding rubber thickness, I'm unsure if 2mm is a necessity, compared to a nice to have.  I'm going to get some and experiment.  I might try Nitrile too.  1/16" might be a perfect fit after it swells a little.  Pretty sure the original seals were Nitrile, and they last for decades so...
Ed

Carburetor O-ring Kits For Sale: Mikuni VM & BS/CV, and Keihin CV34 (as used on KZ750E/H/N/Spectre, 400)

www.kzrider.com/forum/forum-index/faq-wi...owner-things-to-know

1981 KZ750E2
www.kzrider.com/forum/11-projects/604901...z750e-project-thread
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You win a few, and lose a few... 25 Aug 2022 09:28 #872823

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It was obvious to me the plungers weren't that much of a problem. I found it in the air corrector jets. If too rich a couple holes in the emulsion tubes did the trick. One more lesson learned from Miller. RIP. 
Steve
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You win a few, and lose a few... 25 Aug 2022 11:38 #872838

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Hey Zed,
while I DO appreciate your zeal in terms of making your choke plunger rebuilds as good as possible, I'm a little unsure how much details like the grade of Viton matter.  Mikuni used Nitrile for sealing, which works wonderfully because the slight swelling with gas contact affords a good seal.  Could the indent seen on the choke plungers actually be swelling around the seating surface?
Have you ever taken apart some carbs to see if your viton seals are indenting over time?  Regarding rubber thickness, I'm unsure if 2mm is a necessity, compared to a nice to have.  I'm going to get some and experiment.  I might try Nitrile too.  1/16" might be a perfect fit after it swells a little.  Pretty sure the original seals were Nitrile, and they last for decades so...

Here in the UK we are now increasingly forced to used Ethanol "enhanced" fuels and the latest move to E10 has seen E5 now classed as premium and non ethanol super very hard and expensive to find ( the equivalent of over $9 per US gallon ) .
It's a massive con and rip off.
This means that anything less then Viton quickly degrades and falls apart in months rather than years.
This may not be the case in the US and of course if it were not for the Ethanol then using the same material as originally used would be fine.
The indent is exactly that. Compressed rubber which has lost its suppleness ,hardened and taken on a permanent set which eventually allows the plunger to bottom out and does not maintain a consistant seal.
The choice of the Viton replacement material must be of such a shore rating so as not to be so soft that it allows over compression and bottoming out and of sufficient ethanol resistance which B and  F are most suitable in constant contact conditions.
Depending on the climate that the plungers come from and grades of fuel they've be exposed to the condition of the seals vary wildly from a rock solid plastic which need chipping out to a soft swollen like jelly which picks out like an oyster and everything in between.
As for my own Viton seals, I've been doing my own plungers for around 15 years and are in my long term daily ride test bed Z1R which i've run for 22 years and counting.
Whilst you cannot avoid visual evidence of where the plungers are constantly sat against the raised seat in the plunger bore they have remained supple and so far not indented, dimensionally changed or swollen out beyond the original surface.
Depending on the swage height and orifice size of the plunger the thickness of the seal can be crucial.
I have originally tried 1.5mm as it was much easier to install but found that heads with a higher lip and smaller orifice can sit on the rim of the raised bore seat, bottom out and not fully seal.
The early chrome plungers tend to be like that so now i just use the correct 2mm which isn't so hard to fit with the tooling i made and of course the 2mm sits higher than the underside of the retaining bead and almost level with the height of the outer surface due to the inclusion of the seals bevelled edge. 




 

AIR CORRECTOR JETS FOR VM CARBS AND ETHANOL RESISTANT VITON CHOKE PLUNGER SEAL REPLACMENT FOR ALL MIKUNI CARBURETTORS
kzrider.com/forum/23-for-sale/611992-air-corrector-jets-





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You win a few, and lose a few... 26 Aug 2022 17:07 #872917

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Made a set from both nylon and delrin, and delrin is much nicer to cut...

 

BTW, my cat loves the ottoman that I use as a photo background.
Ed

Carburetor O-ring Kits For Sale: Mikuni VM & BS/CV, and Keihin CV34 (as used on KZ750E/H/N/Spectre, 400)

www.kzrider.com/forum/forum-index/faq-wi...owner-things-to-know

1981 KZ750E2
www.kzrider.com/forum/11-projects/604901...z750e-project-thread
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You win a few, and lose a few... 26 Aug 2022 17:37 #872919

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Cool, I have a length of delrin and an old lathe. I'm going to make a new set for my carbs.
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