1980 gs450 petcock question!

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  • JohnESuspekt
    • Feb 2026

    #1

    1980 gs450 petcock question!

    ok, so finally found an oem replacement for my petcock but rather than having one side as off, one reserve and one fuel, it just has reserve and fuel. Where the off button used to be is a gold screw. There is no gas coming from the petcock and if i back the screw out some comes out but leaks out of the screw slightly. Does the screw need to come out and be capped of or something? anyone any ideas?
  • JohnESuspekt

    #2


    heres a pic

    Comment

    • Guest

      #3
      On the front left side of your left carb there should be a nipple there which is the vacuum port. You need a 6mm inside diameter hose for it.

      These are vacuum operated fuel taps so when she fires up it causes a vacuum which sucks open the fuel tap.

      The brass screw is the prime screw. If the carbs are empty, open that for 30 sec's or so to prime with fuel then close it up again.

      You can clearly see in this pic where the vacuum line goes:

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      • JohnESuspekt

        #4
        i have the vacuum line on there but wasnt sure what the screw was for... thanks pete

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        • Guest

          #5
          Originally posted by JohnESuspekt
          i have the vacuum line on there but wasnt sure what the screw was for... thanks pete
          Cool, no worries

          I only just found out a couple of months ago what is was for... all these years I've owned mine I never knew

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          • 7981GS

            #6
            So the OEM petcock on the 450's has a screw to open for Prime?
            Or is that only on the new OEM replacement petcocks available now?

            Daniel

            Comment

            • Guest

              #7
              Originally posted by 7981GS
              So the OEM petcock on the 450's has a screw to open for Prime?
              Or is that only on the new OEM replacement petcocks available now?

              Daniel
              Yup they sure do

              From what I can see the 450's always had this style, whereas the earlier 400's and 425's had the three position tap with the circle as the indicator.

              Going by the price difference on Bouldevard's fiche, I'll stick with the screw style ($78 vs. $258 )...

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              • Hornswaggle

                #8
                FWIW, my '81 450T has the traditional three position petcock - reserve, on, prime and as far as I can tell it is original. Could that be specific to model type E/L/T ?

                Comment

                • Guest

                  #9
                  Originally posted by Hornswaggle
                  FWIW, my '81 450T has the traditional three position petcock - reserve, on, prime and as far as I can tell it is original. Could that be specific to model type E/L/T ?
                  Looks like it was, according to the fiche your model was the only one using that from the 450 range, but it was used on 550's, 650's, and 750's as well...

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                  • Hornswaggle

                    #10
                    Originally posted by pete
                    Looks like it was, according to the fiche your model was the only one using that from the 450 range, but it was used on 550's, 650's, and 750's as well...
                    Thanks Pete, I always knew my bike was special

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                    • Guest

                      #11
                      Originally posted by Hornswaggle
                      Thanks Pete, I always knew my bike was special
                      Hahahaha indeed it is! I still say you got a real nice T there

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                      • terrylee

                        #12
                        My wife's 81 450T also has three position. terrylee

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