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Thread: MIKUNI Choke plunger seat replacement and Air corrector jets for GS fours VM's

  1. #11
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    UPDATE - Plunger reseating service now available for Mikuni 10mm diameter rubber tipped plungers as fitted to most CV's etc and not just the 8mm ones as initially advertised.
    Original post now amended to suit.
    Last edited by zed1015; 02-11-2021 at 03:47 PM.
    Mikuni Viton Choke Plunger Seat Renewal.
    VITON Choke plunger seals .KAWASAKI Z1,Z900,Z650,Z1000,Z1R,SUZUKI GS1000,GSXR,RF | eBay

    Air Corrector Jets for Mikuni VM 24, 26 and 28mm carbs .

    https://www.ebay.co.uk/itm/254380193...84.m1555.l2649




  2. #12
    salty_monk's Avatar
    salty_monk is offline Forum LongTimer GSResource Superstar
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    I will likely bring you mine over next time I visit home

    Where are you based in the UK?

    1980 GS1000G - Sold
    1978 GS1000E - Finished!
    1980 GS550E - Fixed & given to a friend
    1983 GS750ES Special - Sold
    2009 KLR 650 - Sold - gone to TX!
    1982 GS1100G - Rebuilt and finished. - Sold

    www.agadisplay.com
    www.parasiticsanalytics.com

    TWINPOT BRAKE UPGRADE LINKY: http://www.thegsresources.com/_forum...e-on-78-Skunk/

  3. #13
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    Quote Originally Posted by salty_monk View Post
    I will likely bring you mine over next time I visit home

    Where are you based in the UK?
    I'm in North Lincolnshire, Little village in the Isle of Axholme where nobody goes unless they are lost or live there.

    Current shipping from the States is pretty fast despite the Covid and all that..
    Just received a set of plungers from Florida in only four days.
    They will be done and going back out today.
    Mikuni Viton Choke Plunger Seat Renewal.
    VITON Choke plunger seals .KAWASAKI Z1,Z900,Z650,Z1000,Z1R,SUZUKI GS1000,GSXR,RF | eBay

    Air Corrector Jets for Mikuni VM 24, 26 and 28mm carbs .

    https://www.ebay.co.uk/itm/254380193...84.m1555.l2649




  4. #14
    salty_monk's Avatar
    salty_monk is offline Forum LongTimer GSResource Superstar
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    I did a few trackdays at Barkston Heath years ago, closest I've got. Not somewhere I can drop off then! I was hoping you'd be near some of mine or the Mrs family, we usually cast a pretty wide net when we come back.

    1980 GS1000G - Sold
    1978 GS1000E - Finished!
    1980 GS550E - Fixed & given to a friend
    1983 GS750ES Special - Sold
    2009 KLR 650 - Sold - gone to TX!
    1982 GS1100G - Rebuilt and finished. - Sold

    www.agadisplay.com
    www.parasiticsanalytics.com

    TWINPOT BRAKE UPGRADE LINKY: http://www.thegsresources.com/_forum...e-on-78-Skunk/

  5. #15
    bwringer's Avatar
    bwringer is offline Forum LongTimer Bard Award Winner
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    Just bumping this thread because this service needs to be more widely known!
    1983 GS850G, Cosmos Blue.
    2005 KLR685, Aztec Pink - Turd II.3, the ReReReTurdening
    2015 Yamaha FJ-09, Magma Red Power Corrupts...
    Eat more venison.

    Please provide details. The GSR Hive Mind is nearly omniscient, but not yet clairvoyant.

    Celeriter equita, converteque saepe.

  6. #16
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    Eh, so do I understand this correctly; these worn seats cause the choke circuit to leak fuel?

    How to test? Cause mine sure as hell don't look like the provided picture. But I have observed a few of the described issues.
    #1: 1979 GS 550 EC "Red" Very first Bike / Overhaul thread        New here? ☛ Read the Top 10 Newbie mistakes thread
    #2: 1978 GS 550 EC "Blue" Can't make it a donor / "Rebuild" thread     Manuals (and much more): See Cliff's homepage here
    #3: 2014 Moto Guzzi V7 II Racer One needs a runner while wrenching

  7. #17
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    Quote Originally Posted by roeme View Post
    Eh, so do I understand this correctly; these worn seats cause the choke circuit to leak fuel?

    How to test? Cause mine sure as hell don't look like the provided picture. But I have observed a few of the described issues.
    Yes! They go hard and distorted with age and depending on wear you can suffer anything from slight rich running, sooty plugs to very poor running, idling issues, loss of power and increased fuel consumption etc.
    It's tricky to test them ( apart from them being visually indented and hard ) but chances are they are most likely leaking to some degree if they are the rubber tipped type found in MIKUNI carbs and with the use of Ethanol fuel accelerating the seal materials degradation their function will only get worse.
    The one in the pic is from a VM slide carb with metering needle attached as used on early GS's and KZs but some don't have the needle as on some Yamahas etc.
    There is no downside to fitting new seals as i use ethanol resistant Viton which they originally didn't so won't degrade with fuel contact once done and then they can be ruled out of any future fuelling problems.
    I can do any Mikuni plungers and originally developed this to repair the obsolete ones that are no longer produced.
    The plungers for some later machines may still be available from the dealers but chances are the seals are Nitrile and not Viton so will still develop problems with modern fuel..
    Last edited by zed1015; 03-25-2021 at 11:19 AM.
    Mikuni Viton Choke Plunger Seat Renewal.
    VITON Choke plunger seals .KAWASAKI Z1,Z900,Z650,Z1000,Z1R,SUZUKI GS1000,GSXR,RF | eBay

    Air Corrector Jets for Mikuni VM 24, 26 and 28mm carbs .

    https://www.ebay.co.uk/itm/254380193...84.m1555.l2649




  8. #18
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    Ah, thanks for the clarification (Luckily, no ethanol fuel around here unless you specifically seek it out).
    #1: 1979 GS 550 EC "Red" Very first Bike / Overhaul thread        New here? ☛ Read the Top 10 Newbie mistakes thread
    #2: 1978 GS 550 EC "Blue" Can't make it a donor / "Rebuild" thread     Manuals (and much more): See Cliff's homepage here
    #3: 2014 Moto Guzzi V7 II Racer One needs a runner while wrenching

  9. #19
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    This looks like a service I will be seeking out as my bike has most of the classic problems outlined. Sooty plugs, lower than expected mpg, etc., etc., etc.

    I will be in touch in the near future.
    Larry

    '79 GS 1000E
    '93 Honda ST 1100 SOLD-- now residing in Arizona.
    '18 Triumph Tiger 800 (gone too soon)
    '19 Triumph Tiger 800 Christmas 2018 to me from me.

  10. #20
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    Aug 2021
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    Portland, OR
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    Just wanted to say I had a great experience with Rob and his work. He rebuilt the choke plungers for my 1980 GS1000G. The bike had never run under my ownership, so I can't do a before and after comparison but the bike is running now after a full carb rebuild and it seems to be running great! I haven't even vacuum balanced the carbs yet and they already feel like they run like new. No idea if the choke plunger rebuild contributed to this, but it certainly hasn't hurt anything. Thanks Rob, for the peace of mind. He does good work.

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