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1979 GS1000 idles fine but races when the throttle is twisted

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    1979 GS1000 idles fine but races when the throttle is twisted

    I got the bike idling nicely today but when I twist the throttle it races and will not settle down. I can only reduce the idle by turning out the throttle screw but of course that closes the sliders and cannot start the bike without turning it back up. I slackened both sides of the throttle cable but it doesn't make a difference. I can hear the sliders hit top and then bottom when I twist the throttle.

    #2
    1A) (NEW) Trying to diagnose running problems on a bike with an unknown maintenance history. Common maintenance items like clean carbs, properly adjusted valves, no air leaks in the intake system (airbox, carb boots), a clean gas tank (no rust), and a properly functioning petcock are 100% mandatory for the bike to run properly.
    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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      #3
      This is not helpful. I completely dismantled the carbs and replaced all o-rings and gaskets etc.

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        #4
        Did you remove the intake boots and flex them, checking for cracks? Did you replace the O-rings behind the intake boots? Vacuum sync the carbs?
        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


          #5
          I purchased new boots and they included new o-rings. I did a bench sync but haven'd done a vacuum sync yet. One thing I did notice is that the clamps for the air box boots are tightened right up and air may be leaking there. I will buy and install new clamps. I am also looking at the cables - there isn't enough free play. However, the cables are not getting hung up and the slides are dropping to the bottom.

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            #6
            Originally posted by dubwicht View Post
            I purchased new boots and they included new o-rings. I did a bench sync but haven'd done a vacuum sync yet. One thing I did notice is that the clamps for the air box boots are tightened right up and air may be leaking there. I will buy and install new clamps. I am also looking at the cables - there isn't enough free play. However, the cables are not getting hung up and the slides are dropping to the bottom.
            Carbs can be bench synced absolutely fine, but the engine can run like a sack of sadness until the vac gauges are on it.
            Rule of thumb - if you ever disturb the carbs, put the gauges on them.
            There are idiots out there who will tell you it's not necessary. Ignore them, they are braying asses.
            Dave
            '79 GS850GN '80 GS850GT
            Only a dog knows why a motorcyclist sticks his head out of a car window

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              #7
              Thank you for the advice - I will vac sync them.

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