Burbling on decel - K&N?

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  • UncleMike
    • Jan 2026

    #1

    Burbling on decel - K&N?

    Recently cleaned and re-oiled my K&N OEM replacement air filter. Not pods. Found I had most likely over-oiled it when I installed it so I took the advice I'd read on the forum and oiled it quite lightly.

    I've been noticing a burbling when I decel. I've adjusted my mixture screws but now I'm down to around 1-3/4 turns. Everything on the bike is stock, except for the K&N.

    Perhaps I under-oiled it this time and it's causing too much air to flow? I can't imagine needing to richen the mixture on a stock bike more than I have already, or is that normal?

    I can't find any leaks anywhere else. All new boots last year when I re-did the carbs and the airbox has been sealed. Exhaust gaskets, perhaps?
  • Guest

    #2
    As long as it's not popping I wouldn't worry about it.

    Comment

    • UncleMike

      #3
      Originally posted by chef1366
      As long as it's not popping I wouldn't worry about it.
      What's the difference between burbling and popping? It's not a full backfire by any means, but it's definitely sounding a bit like muffled popcorn.

      Just can't seem to get these mixtures screws dialed in right.

      Comment

      • Guest

        #4
        Stock pipes hmmm
        Are you running with the stock pilot jet?

        Comment

        • UncleMike

          #5
          Originally posted by chef1366
          Stock pipes hmmm
          Are you running with the stock pilot jet?
          Yup. Only things changed from stock include the K&N and for my main jets I'm running 122.5s in all four instead of the 120s in 1&4.

          Comment

          • Nessism
            Forum LongTimer
            GSResource Superstar
            Past Site Supporter
            Super Site Supporter
            • Mar 2006
            • 35787
            • Torrance, CA

            #6
            It wouldn't hurt to try 2.5 turns open on the idle mixture screws to richen it up some. Also, oil the filter again. K&N's don't scrub the air that great so it's best to make sure it's well oiled.
            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

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            • UncleMike

              #7
              Originally posted by Nessism
              It wouldn't hurt to try 2.5 turns open on the idle mixture screws to richen it up some. Also, oil the filter again. K&N's don't scrub the air that great so it's best to make sure it's well oiled.
              I was under the impression that turning the screws out would let more air in - clockwise to richen, counter-clockwise to lean.

              Comment

              • Nessism
                Forum LongTimer
                GSResource Superstar
                Past Site Supporter
                Super Site Supporter
                • Mar 2006
                • 35787
                • Torrance, CA

                #8
                Originally posted by UncleMike
                I was under the impression that turning the screws out would let more air in - clockwise to richen, counter-clockwise to lean.
                It's not an air screw, it's a mixture screw. An emulsion of fuel/air comes up the carb passage, which is then metered by the mixture screw before it enters the air stream. Open is richer.
                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

                • UncleMike

                  #9
                  Originally posted by Nessism
                  It's not an air screw, it's a mixture screw. An emulsion of fuel/air comes up the carb passage, which is then metered by the mixture screw before it enters the air stream. Open is richer.
                  What an a**hole I am.

                  Comment

                  • Guest

                    #10
                    Originally posted by UncleMike
                    What an a**hole I am.
                    You are the master of words my friend.
                    With that K&N I bet you should be out 2-2.5 turns out.

                    Comment

                    • UncleMike

                      #11
                      Originally posted by chef1366
                      You are the master of words my friend.
                      With that K&N I bet you should be out 2-2.5 turns out.
                      Thanks guys.

                      Seriously, what an ass.

                      Comment

                      • Nessism
                        Forum LongTimer
                        GSResource Superstar
                        Past Site Supporter
                        Super Site Supporter
                        • Mar 2006
                        • 35787
                        • Torrance, CA

                        #12
                        Hey Mike,
                        If that's the worst thing that happened today I'd call it a great day!
                        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

                        • UncleMike

                          #13
                          Originally posted by Nessism
                          Hey Mike,
                          If that's the worst thing that happened today I'd call it a great day!
                          Good point.

                          I even called a friend for confirmation on this one!

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