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    Replacing Carb Diaphragms?

    I'm going through a set of BS34's where the previous owner used RTV to seal the slide diaphragm's to the carb body. The RTV is holding tenacious to the diaphragm's so replacing them, or the entire slides, seems like the only path forward. The OEM Mikuni slides are fabric covered with rubber. There are a few options for aftermarket diaphragm's including some from JBM industries also options from the UK and China. Those diaphragm's look to be all rubber.

    Has anyone ever traveled this road and if so, what did you decide? Please share.






    .
    Last edited by Nessism; 11-18-2020, 08:48 PM.
    Ed

    To measure is to know.

    Mikuni O-ring Kits For Sale...https://www.thegsresources.com/_foru...ts#post1703182

    Top Newbie Mistakes thread...http://www.thegsresources.com/_forum...d.php?t=171846

    Carb rebuild tutorial...https://gsarchive.bwringer.com/mtsac...d_Tutorial.pdf

    KZ750E Rebuild Thread...http://www.thegsresources.com/_forum...0-Resurrection

    #2
    Originally posted by Nessism View Post
    I'm going through a set of BS34's where the previous owner used RTV to seal the slide diaphragm's to the carb body. The RTV is holding tenacious to the diaphragm's so replacing them, or the entire slides, seems like the only path forward. The OEM Mikuni slides are fabric covered with rubber. There are a few options for aftermarket diaphragm's including some from JBM industries also options from the UK and China. Those diaphragm's look to be all rubber.

    Has anyone ever traveled this road and if so, what did you decide? Please shre.
    I have a set of OEM ones if you need them, bought a set of carbs on ebay but several had broken posts that were JB welded on so using them for parts.

    David.
    2018 Honda Africa Twin AS
    2013 DR 650 Grey, sold 1981 GS 650E Silver,

    1980 GS1000ST Blue & White, X2

    2012 DL650 Vstrom Foxy Orange, in storage
    1981 CT110 X2 "Postie Bikes" Gone to a New Home.
    2002 BMW 1150 GS Blue & White - Sold
    1975 BMW R90/6 Black - Sold 1984 GS1150EF Sold
    1982 BMW R100 Africa trip, Stolen - Recovered- Sold
    1977-1980 Suzuki GS550, GS1000E, GS1000S GSX750, GSX1100,s
    Hondas ST90, CR125 CB175 , CB350 CB750, NSU Quickly, Yamaha RD's 350/400,

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      #3
      The only bike ive replaced them on is the 77 Yammy XS750. I oiled the lip that goes between the plastic rings and stretched the diaphrams to work them into the rings. Once in go around them a few times and spot stretch them again to be sure they are fully seated against the slides.
      MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
      1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

      NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


      I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

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        #4
        If/when you do get the new diaphrams on, make sure they are clocked correctly.

        When the tab on the diaphragm is in its notch, the vent hole in the bottom of the slide should be directly downstream from the needle.

        .
        sigpic
        mine: 2000 Honda GoldWing GL1500SE and 1980 GS850G'K' "Junior"
        hers: 1982 GS850GL - "Angel" and 1969 Suzuki T250 Scrambler
        #1 son: 1986 Yamaha Venture Royale 1300 and 1982 GS650GL "Rat Bagger"
        #2 son: 1980 GS1000G
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          #5
          Before ordering new diaphragms I thought I'd better make my best effort towards removing the RTV. Tried an over night soak in mineral spirits but that did virtually nothing.
          Ed

          To measure is to know.

          Mikuni O-ring Kits For Sale...https://www.thegsresources.com/_foru...ts#post1703182

          Top Newbie Mistakes thread...http://www.thegsresources.com/_forum...d.php?t=171846

          Carb rebuild tutorial...https://gsarchive.bwringer.com/mtsac...d_Tutorial.pdf

          KZ750E Rebuild Thread...http://www.thegsresources.com/_forum...0-Resurrection

          Comment


            #6
            I wonder if gasoline might do it...silicone based stuff is not good with gas I think.

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