GS450 carb woes

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  • rangerdanger
    • Feb 2026

    #1

    GS450 carb woes

    so this is a new issue, even for me. I purchased a set of used carbs online, rebuilt completely with OEM gaskets and o-rings, stuck em on the bike and ran AWESOME!

    Tuesday night, bike ran perfect. Wed morning i get a phone call from my girlfriend saying that the bike is leaking. Wonderful.

    So i went down and looked, the bike is literally, pouring, fuel out of the number 2 carb vent, and struggling to fire. Where do i even start?
  • Dave8338
    Forum LongTimer
    Past Site Supporter
    • Aug 2006
    • 11608
    • Annandale, MN

    #2
    Originally posted by rangerdanger
    so this is a new issue, even for me. I purchased a set of used carbs online, rebuilt completely with OEM gaskets and o-rings, stuck em on the bike and ran AWESOME!

    Tuesday night, bike ran perfect. Wed morning i get a phone call from my girlfriend saying that the bike is leaking. Wonderful.

    So i went down and looked, the bike is literally, pouring, fuel out of the number 2 carb vent, and struggling to fire. Where do i even start?
    Replace your petcock, with a new one. That or try to tap the side of the float bowl for #2 and see if it is just a float hanging up.

    My money would be on the petcock...

    Comment

    • Guest

      #3
      Could be the float valve too.

      Number 2 on a 450 doesn't have the vacuum port, so not sure if that rules the fuel tap out or not...

      Comment

      • koolaid_kid

        #4
        What was the petcock set to, PRI, RES or ON?
        If it was set to either ON or RES the petcock is faulty. By design it should not flow any fuel unless there is vacuum on the vacuum line, which only occurs when the engine is running.
        If it was set to PRI there may not be anything wrong at all.

        Comment

        • rangerdanger

          #5
          petcock was set to ON. bike does not flow fuel with the engine not running.

          Im just at a loss because this is like..50 miles after a COMPLETE overhaul. clean everything, weird.

          Comment

          • tom203
            Forum Guru
            Past Site Supporter
            • Aug 2010
            • 8925
            • Norway,Maine

            #6
            Originally posted by rangerdanger
            petcock was set to ON. bike does not flow fuel with the engine not running.

            Im just at a loss because this is like..50 miles after a COMPLETE overhaul. clean everything, weird.
            There's only one place for the fuel to keep flowing from...... that's right ,the petcock! Not convinced, disconnect both lines from tank, add some gas ,and be patient.
            1981 gs650L

            "We are all born ignorant, but you have to work hard to stay stupid" Ben Franklin

            Comment

            • koolaid_kid

              #7
              I agree with Tom. You only have a sample size of 1, which is not enough to state that the petcock does not flow. You have a sample size of 1 which showed it will flow with the engine off. That should be enough to realize that it are bustificated. Get a new OEM unit and wait another 30 years for it to start leaking again. Also, take a whiff of your oil. It is entirely likely that it smells like gas. If so, time for an oil and filter change.

              Comment

              • Nessism
                Forum LongTimer
                GSResource Superstar
                Past Site Supporter
                Super Site Supporter
                • Mar 2006
                • 35788
                • Torrance, CA

                #8
                Rust in the gas tank fouling the #2 float needle?
                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

                • Dave8338
                  Forum LongTimer
                  Past Site Supporter
                  • Aug 2006
                  • 11608
                  • Annandale, MN

                  #9
                  Originally posted by Nessism
                  Rust in the gas tank fouling the #2 float needle?
                  Was my mention for the "rap on it and see" comment.

                  Still...if the petcock is working correctly and is set to ON or RES, there will be no fuel to leak past the seat, other than what is in the line and I doubt that would happen to the extend that he explains.

                  Never know...

                  Comment

                  • rangerdanger

                    #10
                    Figured it out.

                    Comment

                    • koolaid_kid

                      #11
                      Oops. Is is fixable?

                      Comment

                      • rangerdanger

                        #12
                        Hard to tell. I could attempt at soldering the seals. May be more reliable to just buy a new float.

                        Comment

                        • koolaid_kid

                          #13
                          You could try the parts wanted section here. There are lots of carb guys here, perhaps someone can help you out with a gently used float.

                          Comment

                          • Nessism
                            Forum LongTimer
                            GSResource Superstar
                            Past Site Supporter
                            Super Site Supporter
                            • Mar 2006
                            • 35788
                            • Torrance, CA

                            #14
                            I'd solder it. Get some plumbing solder. Not the stuff for electrical bits. And test for leaks afterwards.
                            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

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