no carb synch screw

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  • lurch12_2000
    • Feb 2026

    #1

    no carb synch screw

    Amongst other things, I will be synching the carbs on an '83 650G Katana and noticed that the PO had replaced the intake boots. That's good except that the #3 intake does not have a synch allen screw hole to hook up the tool's vacuum tube, just the #1,2, and 4 carbs?
    The pdf manual shows 4 screws and now I am wondering why someone would order a set of new intake boots with one not having a carb synch port? They are marked right and left and appear to be correct position otherwise. So now only being able to hook up 3 tubes from my Carbtune, what would be a proper procedure to synch them?...just #1 to #4 and then #2 slightly lower to them, and assume #3 is correct?
    Last edited by Guest; 05-18-2009, 09:06 AM.
  • bwringer
    Forum LongTimer
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    • Oct 2003
    • 17066
    • Indianapolis

    #2
    Is the sync port screw just missing?

    That would also make it run kinda poopy.
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    Comment

    • Bribird

      #3
      Thats a strange problem. I would think you will need to attach that vac hose to something... you may need to order a new intake boot. i would check it very carefully and make sure the one that is missing the port doesnt have it on the backside of where it should be...?? I may a used one that is in pretty good shape at the shop..... I bought all 4 new ones for my bike during the build. I could send you one, use it to balance your carbs.. then pull it back off and put your new, no vac port intake back on.

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      • Guest

        #4
        Hook #3 up to the vacuum port for the petcock.

        Comment

        • Bribird

          #5
          Originally posted by renobruce
          Hook #3 up to the vacuum port for the petcock.

          Hey! thats the easy way!! forgot all about the bonus vacuum port on the #3 carb.

          Comment

          • skidMarkNZ

            #6
            Originally posted by Bribird
            Hey! thats the easy way!! forgot all about the bonus vacuum port on the #3 carb.

            it's on #2 on the 650's....

            Comment

            • Guest

              #7
              Originally posted by skidMarkNZ
              it's on #2 on the 650's....
              Well, that sucks.

              Sounds like you need to order the proper boot.

              Comment

              • Guest

                #8
                OR...maybe you can flip the boots upside-down and put the left on the right and visaversa. That would leave #2 with a boot without a port, and you can hook up to the vacuum for the petcock.

                I did this with some kawasaki boots for my Skunk because the ports wouldn't work the normal way. You may not have any room to hook up your synch tubes...you'll have to check.

                Comment

                • tkent02
                  Forum LongTimer
                  Past Site Supporter
                  • Jan 2006
                  • 35571
                  • Near South Park

                  #9
                  Drill a hole in the intake runner in the head, tap it, yer done.
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                  Life is too short to ride an L.

                  Comment

                  • TheCafeKid

                    #10
                    Originally posted by bwringer
                    Is the sync port screw just missing?

                    That would also make it run kinda poopy.
                    Huh huh...he said poopy....

                    Comment

                    • lurch12_2000

                      #11
                      Originally posted by bwringer
                      Is the sync port screw just missing?

                      That would also make it run kinda poopy.
                      No, the boot just does not have a hole.
                      So I guess if the petcock vacuum port is off #2 then I will have to drill and tap a hole or get a new boot. The boots are correct with 2 marked L and 2 marked R and mounted properly.

                      Comment

                      • Guest

                        #12
                        I didn't look at the parts fiche, but my 750LX shows L & R intake boots as well. However, the superseded p/n's are the same boot for both sides.

                        If that's the same with yours, you can switch 2 with 3 and then you're back to using the petcock vaccum line for 2.

                        Just a thought.

                        Good luck

                        Comment

                        • waltfen
                          Forum Mentor
                          • Oct 2007
                          • 106
                          • Winteringham, England

                          #13
                          Originally posted by hikermikem
                          I didn't look at the parts fiche, but my 750LX shows L & R intake boots as well. However, the superseded p/n's are the same boot for both sides.

                          If that's the same with yours, you can switch 2 with 3 and then you're back to using the petcock vaccum line for 2.

                          Just a thought.

                          Good luck
                          2 left boots are definitely different to the 2 right boots. You could swap 1 with 2 or 3 with 4, but no other options are available.

                          What may help you is that the GS550 with CV carbs uses the same boots.

                          Part numbers :-
                          Left - 13120-47010
                          Right - 13110 - 47010
                          Last edited by waltfen; 05-18-2009, 10:56 AM.
                          GS1000G

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                          • lurch12_2000

                            #14
                            Not sure if this suggestion has been posted but here is a pic of the setup for the tank off the bike and resting nicely on a saw horse awaiting carb synch. Got this suggestion from my nephew while we're waiting for a few replacement shims to finish the valve adjustment first. The 2 ft piece of clear hose will go to the vacuum port and the 2 ft black hose to the fuel port on the petcock. It fits the tank tunnel perfect, sits at the right height, and I have a bungee(not shown) around the back end of the tank for extra precaution if I walk into it!

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