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1980 GS-550 throttle problems

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    #1

    1980 GS-550 throttle problems

    Hi,
    Just bought this bike and notice that when I'm at highway speeds, between 55 - 75 mph, the bike will start to lose power as I approach ~ 75 mph. Most of the time what happens is that I chug along with the bike bouncing between ~ 50 - 70 mph, keeping the throttle constant as if I'm trying to be at 70mph. As it approaches the upper speed range, it just seems to start slowing down on its own. When it gets down around 50, it stays there a while and then starts speeding up again (assuming I'm still throttled for 70).

    Could this be a points issue? I'm not sure when they were adjusted last. What else should I check?

    Thanks
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    #2
    Have you tried dropping a gear and holding the RPM's where they would be at 70mph? Reason I ask, it is a great way to check for fuel starvation. Fuel filter...Float level...crimped fuel line...ect.

    Comment

      #3
      Originally posted by ra5467 View Post
      Could this be a points issue? I'm not sure when they were adjusted last. What else should I check?

      Thanks
      80 GS550 has electronic ignition. No points.
      Check the minor things first: Vacuum line to the petcock, fuel cap vent, crimped fuel line, rust in the tank, decent spark plugs etc.
      Last edited by Guest; 08-29-2006, 02:36 PM.

      Comment

        #4
        Originally posted by 8trackmind View Post
        80 GS550 has electronic ignition. No points.
        Check the minor things first: Vacuum line to the petcock, fuel cap vent, crimped fuel line, rust in the tank, decent spark plugs etc.


        from what i remember when the last time this happened, dropping down a gear causes RPMs to temporarily increase and then, as bike loses more power, speed & RPMs decrease. If there was physically something wrong with fuel delivery, why would it only impact the bike at higher speeds?

        thanks

        Comment

          #5
          Might be fuel starvation caused by a bad petcock. My bike did the same thing and eventually started dying all together. A new petcock fixed me up
          1983 GS 1100E w/ 1230 kit, .340 lift Web Cams, Ape heavy duty valve springs, 83 1100 head with 1.5mm oversized SS intake valves, 1150 crank, Vance and Hines 1150 SuperHub, Star Racing high volume oil pump gears, 36mm carebs Dynojet stage 3 jet kit, Posplayr's SSPB, Progressive rear shocks and fork springs, Dyna 2000, Dynatek green coils and Vance & Hines 4-1 exhaust.
          1985 GS1150ES stock with 85 Red E bodywork.

          Comment

            #6
            The higher the RPMS...the more fuel you are consuming. If their is a blockage in the fuel delivery system ie. crimped lines, clogged fuel filter, or the float level being set too low, you are simply running the bike out of fuel. When you slow down, th system has a chance to recover and your RPMs return. If your fuel vent in the gas cap were clogged, the bike would opperate fine through all RPM ranges until the vaccume within the tank reached a point that its pull would equal that of gravity (no fuel pump on my GS) and the bike would stall as you describe. It would not restart until you either opened the gas cap or it drew in enough air in through some other means.

            My guess is either a clogged fuel filter on the petcock in the tank, or the float level is set too low.

            Tconroy...any additional thoughts?

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