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    Mikuni BS32 throttle plate opening at idle

    Got an '82 GS650GL, Mikuni BS32's, recently un-ganged and dipped. Everything is shiny and reassembled now with fresh brass and o-rings.
    My only question is... How far should I screw the idle adjuster in? Or... How open should the throttle plates be on first firing?
    My guess is just a "smidge." Basically the diameter of the straitened out pin I used to bench sync them prior to un-ganging.

    Even if it doesn't matter, I'd still like to hear what people think.
    Last edited by Guest; 03-30-2017, 09:49 PM.

    #2
    Do you have them on the bike yet? If not, re-do the bench sync, but use LIGHT, rather than anything solid to check the openings.

    Hold the carbs up to a light or a bright wall, have the engine side towards you. If you look through the carbs, you will see a sliver of light at the bottom of the plates. By moving the idle speed screw, you can see which carb approaces closed first, then sync the others to that. I find this MUCH more accurate than a pin, paper clip or any other mechanical device.

    When you are done with that, back the idle speed adjuster out until it does not touch the carb linkage (cam?), then turn it until it just touches, plus 2 turns. It might be a bit too much, so be ready with the KILL switch when you try to start it.

    .
    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
    Family Portrait
    Siblings and Spouses
    Mom's first ride
    Want a copy of my valve adjust spreadsheet for your 2-valve per cylinder engine? Send me an e-mail request (not a PM)
    (Click on my username in the upper-left corner for e-mail info.)

    Comment


      #3
      Hey! Thank you so much for that! It makes a lot of sense.

      The carbs are still sitting on a table so I'm gonna go get to it now!

      Comment


        #4
        Here is what you will be looking for, the sliver of light under the plate:



        .
        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
        Family Portrait
        Siblings and Spouses
        Mom's first ride
        Want a copy of my valve adjust spreadsheet for your 2-valve per cylinder engine? Send me an e-mail request (not a PM)
        (Click on my username in the upper-left corner for e-mail info.)

        Comment


          #5
          Originally posted by Steve View Post
          Do you have them on the bike yet? If not, re-do the bench sync, but use LIGHT, rather than anything solid to check the openings.

          Hold the carbs up to a light or a bright wall, have the engine side towards you. If you look through the carbs, you will see a sliver of light at the bottom of the plates. By moving the idle speed screw, you can see which carb approaces closed first, then sync the others to that. I find this MUCH more accurate than a pin, paper clip or any other mechanical device.

          When you are done with that, back the idle speed adjuster out until it does not touch the carb linkage (cam?), then turn it until it just touches, plus 2 turns. It might be a bit too much, so be ready with the KILL switch when you try to start it.

          .
          Works for me. Pretty much the same way I do the initial bench sync.

          1980 GS1000GT (Daily rider with a 1983 1100G engine)
          1998 Honda ST1100 (Daily long distance rider)
          1982 GS850GLZ (Daily rider when the weather is crap)

          Darn, with so many daily riders it's hard to decide which one to jump on next.

          JTGS850GL aka Julius

          GS Resource Greetings

          Comment


            #6
            Originally posted by Tony View Post
            Got an '82 GS650GL, Mikuni BS32's, recently un-ganged and dipped. Everything is shiny and reassembled now with fresh brass and o-rings.
            My only question is... How far should I screw the idle adjuster in? Or... How open should the throttle plates be on first firing?
            My guess is just a "smidge." Basically the diameter of the straitened out pin I used to bench sync them prior to un-ganging.

            Even if it doesn't matter, I'd still like to hear what people think.
            Exactly what do yo mean by "fresh brass"? I hope you didn't install new aftermarket jets.

            1980 GS1000GT (Daily rider with a 1983 1100G engine)
            1998 Honda ST1100 (Daily long distance rider)
            1982 GS850GLZ (Daily rider when the weather is crap)

            Darn, with so many daily riders it's hard to decide which one to jump on next.

            JTGS850GL aka Julius

            GS Resource Greetings

            Comment


              #7
              Originally posted by JTGS850GL View Post
              Exactly what do yo mean by "fresh brass"? I hope you didn't install new aftermarket jets.
              Good catch, JT, I missed that when I glanced through.
              .
              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
              Family Portrait
              Siblings and Spouses
              Mom's first ride
              Want a copy of my valve adjust spreadsheet for your 2-valve per cylinder engine? Send me an e-mail request (not a PM)
              (Click on my username in the upper-left corner for e-mail info.)

              Comment


                #8
                Well, you can thank the PO for not including anything original or even close to a correct size. Unless I get my hands on a time machine, these OEM equivalents from Jets 'R Us will just have to do the trick.

                But I appreciate your input.

                Comment


                  #9
                  Originally posted by Tony View Post
                  Well, you can thank the PO for not including anything original or even close to a correct size. Unless I get my hands on a time machine, these OEM equivalents from Jets 'R Us will just have to do the trick.

                  But I appreciate your input.
                  Jets R Us sells OEM for just a couple bucks more then the knock offs. The OEMs are well worth the price difference.

                  1980 GS1000GT (Daily rider with a 1983 1100G engine)
                  1998 Honda ST1100 (Daily long distance rider)
                  1982 GS850GLZ (Daily rider when the weather is crap)

                  Darn, with so many daily riders it's hard to decide which one to jump on next.

                  JTGS850GL aka Julius

                  GS Resource Greetings

                  Comment


                    #10
                    Originally posted by JTGS850GL View Post
                    Jets R Us sells OEM for just a couple bucks more then the knock offs. The OEMs are well worth the price difference.
                    Wow, I didn't realize that the two columns were different types. I bought from the left side thinking they were all just "equivalents" and that the list just continued on the right side. I'm surprised, yet grateful, that Mikuni still supplies such things.

                    I also checked my fittings for the mikuni double-square stamp and they have them. So rest easy guys and thanks for the tips!

                    Comment


                      #11
                      Originally posted by Tony View Post
                      Wow, I didn't realize that the two columns were different types. I bought from the left side thinking they were all just "equivalents" and that the list just continued on the right side. I'm surprised, yet grateful, that Mikuni still supplies such things.

                      I also checked my fittings for the mikuni double-square stamp and they have them. So rest easy guys and thanks for the tips!
                      Good to hear. Sometimes you just get lucky.

                      1980 GS1000GT (Daily rider with a 1983 1100G engine)
                      1998 Honda ST1100 (Daily long distance rider)
                      1982 GS850GLZ (Daily rider when the weather is crap)

                      Darn, with so many daily riders it's hard to decide which one to jump on next.

                      JTGS850GL aka Julius

                      GS Resource Greetings

                      Comment

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