Increasingly high idle from cold start...

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  • JackPanzer
    XSive
    • Apr 2014
    • 28
    • Amarillo, TX.

    #1

    Increasingly high idle from cold start...

    Well guys, I got my leaking problem fixed...now I got another one stumping me. Whenever I rode my bike around yesterday it seemed to run decent aside from needing carb synching. I let it rest a bit and came back to it last night and started it up, bam, high rpms amd they increased dramatically over a few seconds. Pulling the choke slowed it down then increased it again. Adjusted the butterflies to as close as I could off the bike and replaced then, turned the mixture screws until they seated and tried it again. Worked for a few seconds then the same things happened; high (3k+) idle and continually increased until I shut the bike off. Throttle cable does need lubed but it isn't sticking. I don't have money to get starting fluid until next Friday and Google is failing me. Am I just missing something simple or do I just need to bite the bullet and take it to a mechanic when I have money?
    79 SF
  • rdmcguy
    XSive Maximus
    • Jul 2013
    • 515
    • Denver, Colo.

    #2
    increasing idle speed

    You didn't mention if you turned the idle mixture screws back out.
    sounds lean to me or air leak possibly at the manifolds or starving for fuel
    spray some wd 40 on manifolds at idle and see if things change.
    There are a lot of variables it could be .
    Start with clean carbs,no air leaks bench synch,no snagging or sticking cables
    idle screw set correctly.
    One thing at a time.
    Good luck
    78standard,79 & 80 Specials; 2 x 650 Maxims; 4 x RD350's; yz450; 2 x Honda tlr's;2x jt1 mini.

    Comment

    • BA80
      Doctor of XSology
      • Oct 2010
      • 9980
      • Tulsa, Ok

      #3
      Does the idle increase without you moving the throttle at all or does it seem to increase a little more each time you rev it?
      Greg

      Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

      ― Albert Einstein

      80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

      The list changes.

      Comment

      • JackPanzer
        XSive
        • Apr 2014
        • 28
        • Amarillo, TX.

        #4
        Originally posted by BA80
        Does the idle increase without you moving the throttle at all or does it seem to increase a little more each time you rev it?
        It imcreases withoit me moving at all. I backed out the mixture screws quite a bit. Same thing. Nothing changed with WD-40. Gonna break 'em back down and see what I did between yesterday afternoon and last night.
        79 SF

        Comment

        • JackPanzer
          XSive
          • Apr 2014
          • 28
          • Amarillo, TX.

          #5
          Originally posted by rdmcguy
          You didn't mention if you turned the idle mixture screws back out.
          sounds lean to me or air leak possibly at the manifolds or starving for fuel
          spray some wd 40 on manifolds at idle and see if things change.
          There are a lot of variables it could be .
          Start with clean carbs,no air leaks bench synch,no snagging or sticking cables
          idle screw set correctly.
          One thing at a time.
          Good luck
          Appreciate the advice. I do just need to take it slow. Just being impatient.
          79 SF

          Comment

          • BA80
            Doctor of XSology
            • Oct 2010
            • 9980
            • Tulsa, Ok

            #6
            The reason I asked was I've seen throttle linkage hanging on boot clamps many times. It usually will be a throttle movement that will change the speed.

            The engine speed CANNOT increase without more air being allowed into the cylinder. It can only put out what it takes in. It doesn't create it. There are only a couple places it can come from.

            1: Obviously the butterfly valves in the carb throat.

            2; Vacuum leaks ( boots, nipples, clamps not sealing).

            A set of carbs not properly, or at least closely, synced will act that way.
            Greg

            Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

            ― Albert Einstein

            80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

            The list changes.

            Comment

            • JackPanzer
              XSive
              • Apr 2014
              • 28
              • Amarillo, TX.

              #7
              Originally posted by BA80
              The reason I asked was I've seen throttle linkage hanging on boot clamps many times. It usually will be a throttle movement that will change the speed.

              The engine speed CANNOT increase without more air being allowed into the cylinder. It can only put out what it takes in. It doesn't create it. There are only a couple places it can come from.

              1: Obviously the butterfly valves in the carb throat.

              2; Vacuum leaks ( boots, nipples, clamps not sealing).

              A set of carbs not properly, or at least closely, synced will act that way.
              I'm checking the boots after a quick run for a burger. I'll be bench synching as best I can whilst I do that. But unfortunately neighbours complaining about noise. Too late to start it up again tonight. Will let you know how it progresses. Thank you again.
              79 SF

              Comment

              • BA80
                Doctor of XSology
                • Oct 2010
                • 9980
                • Tulsa, Ok

                #8
                Greg

                Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

                ― Albert Einstein

                80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

                The list changes.

                Comment

                • JackPanzer
                  XSive
                  • Apr 2014
                  • 28
                  • Amarillo, TX.

                  #9
                  Haha, that'sthe method I used. Split the first hole down the middle.
                  79 SF

                  Comment

                  • BA80
                    Doctor of XSology
                    • Oct 2010
                    • 9980
                    • Tulsa, Ok

                    #10
                    Doesn't it make any difference if you back the idle screw down?

                    I know when I start my bike up I use the throttle lock to keep the thing running (without the choke) while it warms up because it won't idle cold. As it warms up, if I'm not there to slow it down, it'll gradually increase to 3500 - 4000 RPMs.

                    I don't like using the choke because it kills plugs FAST.
                    Greg

                    Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

                    ― Albert Einstein

                    80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

                    The list changes.

                    Comment

                    • JackPanzer
                      XSive
                      • Apr 2014
                      • 28
                      • Amarillo, TX.

                      #11



                      Well....I have found one issue.
                      79 SF

                      Comment

                      • BA80
                        Doctor of XSology
                        • Oct 2010
                        • 9980
                        • Tulsa, Ok

                        #12
                        Originally posted by JackPanzer



                        Well....I have found one issue.
                        Your picture didn't show and I can't pull it up.
                        Greg

                        Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

                        ― Albert Einstein

                        80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

                        The list changes.

                        Comment

                        • JackPanzer
                          XSive
                          • Apr 2014
                          • 28
                          • Amarillo, TX.

                          #13
                          Originally posted by BA80
                          Your picture didn't show and I can't pull it up.


                          Sorry about that.
                          Last edited by JackPanzer; 04-24-2014, 07:22 PM. Reason: mistake
                          79 SF

                          Comment

                          • JackPanzer
                            XSive
                            • Apr 2014
                            • 28
                            • Amarillo, TX.

                            #14
                            Originally posted by BA80
                            Doesn't it make any difference if you back the idle screw down?

                            I know when I start my bike up I use the throttle lock to keep the thing running (without the choke) while it warms up because it won't idle cold. As it warms up, if I'm not there to slow it down, it'll gradually increase to 3500 - 4000 RPMs.

                            I don't like using the choke because it kills plugs FAST.
                            It's a huge increase in a short amount of time. It's acting like I'm pegging the throttle. Many k's of rpms increase. I can only turn the bike on for a few seconds at a time.
                            79 SF

                            Comment

                            • BA80
                              Doctor of XSology
                              • Oct 2010
                              • 9980
                              • Tulsa, Ok

                              #15


                              Not exactly sure what your trying to show here. If your host has an IMG code, use that.
                              Greg

                              Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

                              ― Albert Einstein

                              80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

                              The list changes.

                              Comment

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