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  • #1

    Carb Sync Issues

    Finally got my MNS carbs to stop leaking gas out of the float bowls but I'm having should trouble bench (pre-)syncing them. I followed the guide on here for pre-syncing them in the tech-tips but I'm having a strange problem.

    When I go to set the #1 carb butterfly even with the screw all the way turned in it will still not open the butterfly enough to match the gap with the other three carbs. I'm not sure if there is a way to reset the adjustment but I can't adjust the part that turns it since it is slotted to only fit in at a certain angle.

    Any ideas why the #1 butterfly would not be able to open as far as the others?

    They are a set of 1980 MNS carbs for reference.
    78 E - 2to1 exhaust, dynatek coils, special headlight [SOLD!]
    79 F - gas tank refurb, headgasket change, straight pipes, late model carbs, virago lowering shocks, special headlight and gauges, TC fuse block, GSXR-1100 carbs (WIP)


    "May my tires not fail me, nor my engine grow cold"
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  • #2
    Are you using this thread as a guide? http://www.xs11.com/forum/showthread.php?t=88
    2-79 XS1100 SF
    2-78 XS1100 E Best bike Ever
    80 XS 1100 SG Big bore kit but not fully running yet.
    Couple of more parts bikes of which 2 more will live!

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    • #3
      This one is better.... http://www.xs11.com/forum/showthread.php?t=36021

      The only reason I can think of why you can't adjust that is you don't have the #1 carb linkage engaged right with #2. Pics would helps....
      Fast, Cheap, Reliable... Pick any two

      '78E original owner - resto project
      '78E ???? owner - Modder project FJ forks, 4-piston calipers F/R, 160/80-16 rear tire
      '82 XJ rebuild project
      '80SG restified, red SOLD
      '79F parts...
      '81H more parts...

      Other current bikes:
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      • #4
        Originally posted by crazy steve View Post
        This one is better.... http://www.xs11.com/forum/showthread.php?t=36021

        The only reason I can think of why you can't adjust that is you don't have the #1 carb linkage engaged right with #2. Pics would helps....
        Ooo...that is better. I'm going to give that one a try and take pictures if/when it doesn't work out.
        78 E - 2to1 exhaust, dynatek coils, special headlight [SOLD!]
        79 F - gas tank refurb, headgasket change, straight pipes, late model carbs, virago lowering shocks, special headlight and gauges, TC fuse block, GSXR-1100 carbs (WIP)


        "May my tires not fail me, nor my engine grow cold"

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        • #5
          OK, so I'll ask the stupid question, are you sure your using the right screw? down in the tunnel is the mixture screw, that adjust the fuel ratio at low speed / idle. Further down, between the carbs is the synch screw, that screw adjust the difference in butterfly plate position between the two carbs it adjoins.
          Life is what happens while your planning everything else!

          When your work speaks for itself, don't interrupt.

          81 XS1100 Special - Humpty Dumpty
          80 XS1100 Special - Project Resurrection


          Previously owned
          93 GSX600F
          80 XS1100 Special - Ruby
          81 XS1100 Special
          81 CB750 C
          80 CB750 C
          78 XS750

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          • #6
            Originally posted by DGXSER View Post
            OK, so I'll ask the stupid question, are you sure your using the right screw? down in the tunnel is the mixture screw, that adjust the fuel ratio at low speed / idle. Further down, between the carbs is the synch screw, that screw adjust the difference in butterfly plate position between the two carbs it adjoins.
            On the MNS carbs there aren't idle mixture screws from what I can tell, right? They have caps over them and you'd have to drill them out according to this:
            http://www.knez.org/photos/photoinde...carb%20balance

            With idle screws:


            Without idle screws:


            But yes, I am adjusting the right screw and I don't blame you for asking
            78 E - 2to1 exhaust, dynatek coils, special headlight [SOLD!]
            79 F - gas tank refurb, headgasket change, straight pipes, late model carbs, virago lowering shocks, special headlight and gauges, TC fuse block, GSXR-1100 carbs (WIP)


            "May my tires not fail me, nor my engine grow cold"

            Comment

            • #7
              To get the carbs set up right you need to remove those caps and get to the mix screws.

              Plus you can't fully clean the carbs without removing those.
              Last edited by natemoen; 12-03-2013, 12:43 PM.
              Nathan
              KD9ARL

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              1978 XS1100E
              K&N Filter
              #45 pilot Jet, #137.5 Main Jet
              OEM Exhaust
              ATK Fork Brace
              LED Dash lights
              Ammeter, Oil Pressure, Oil Temp, and Volt Meters
              Green Monster Coils
              SS Brake Lines
              Vision 550 Auto Tensioner

              In any moment of decision the best thing you can do is the right thing, the next best thing is the wrong thing, and the worst thing you can do is nothing.

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              • #8
                Ok, just to clarify for you, Other than the bodies being painted black and the diaphragm covers being gold, there is no difference between MNS carbs and all other 80-81 model carbs. All of the 80-81 carbs came with the pilot air jet/mixture screws having those caps over them. And yes, you need to drill them and put a screw in the hole to pull them out so you can adjust the mixture.

                The pic With Idle screws shows the 78-79 model carbs, the lower pic shows the 80-81 model carbs. They have screws, they are just down inside the tunnel under those caps.

                Glad your adjusting the correct screw. The way I always go through this is to start by adjusting the idle adjustment screw (which controls the no 3 carb butterfly) so the butterfly on 3 is where I want it. I tend to use the small wire/bread tie method. I then move on to adjust 2 and 4 butterflies to the same opening, then adjust 1.
                Last edited by DGXSER; 12-03-2013, 02:25 PM.
                Life is what happens while your planning everything else!

                When your work speaks for itself, don't interrupt.

                81 XS1100 Special - Humpty Dumpty
                80 XS1100 Special - Project Resurrection


                Previously owned
                93 GSX600F
                80 XS1100 Special - Ruby
                81 XS1100 Special
                81 CB750 C
                80 CB750 C
                78 XS750

                Comment

                • #9
                  Originally posted by crazy steve View Post
                  This one is better.... http://www.xs11.com/forum/showthread.php?t=36021

                  The only reason I can think of why you can't adjust that is you don't have the #1 carb linkage engaged right with #2. Pics would helps....
                  I realize your link is better if you are setting them up and know the correct procedure. My point in posting the other was to be sure he was doing the procedure right and not turning the wrong screws or something silly.
                  While the thread you point to is better, I wonder if we could maybe add to it in some way that shows the procedure to get the butterflies to that point. JAT as many do not look for more info, and just dive into the deep end.
                  2-79 XS1100 SF
                  2-78 XS1100 E Best bike Ever
                  80 XS 1100 SG Big bore kit but not fully running yet.
                  Couple of more parts bikes of which 2 more will live!

                  Comment

                  • #10
                    Butterfly adjustment

                    Originally posted by D0wn5h1ft View Post
                    Ooo...that is better. I'm going to give that one a try and take pictures if/when it doesn't work out.
                    Just hold them up to the light so you can see the gap per the light of the silvery moon as you adjust until all are equal.
                    76 XS650 C ROADSTER
                    80 XS650 G Special II
                    https://ibb.co/album/icbGgF
                    80 XS 1100 SG
                    81 XS 1100LH/SH DARKHORSE
                    https://tinyurl.com/k6nzvtw
                    AKA; Don'e, UD, Unca Don'e

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