80 GS550: Why are there plugs in the pilot jet tubes?

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  • Speed_Demon

    #1

    80 GS550: Why are there plugs in the pilot jet tubes?

    I have a 1980 GS550L running the stock Mikuni CV carbs. The bike was given to me in pieces. I cleaned out the carbs and it runs smooth but dies if I let it idle for more than a few seconds. If I crank it for a while with the choke on and pull the plugs they are perfectly dry. Its definately a fuel starvation issue.

    The second time I pull the carbs I pay more attention to the plugs. As far as I can tell there is no functional low-speed curcuit with the plugs installed.

    What are these black plugs and should they be there?
  • Guest

    #2
    They do need to be there. There is a small passage way that connects the pilot circuit with the main jet. Maybe this is is plugged. Also did you check valve clearance, bench sync your carbs, adjust each idle mixture screw with the highest rpm method and then sync the carbs with a manometer.

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    • Speed_Demon

      #3
      Originally posted by chef1366
      They do need to be there. There is a small passage way that connects the pilot circuit with the main jet. Maybe this is is plugged. Also did you check valve clearance, bench sync your carbs, adjust each idle mixture screw with the highest rpm method and then sync the carbs with a manometer.
      The valve clearances are fine and the carbs are sync'ed. These carbs don't have an idle mixture screw. They are preset from the factory and not adjustable.

      As far as the connection to the main jet curcuit thats good info.

      Please keep it coming.

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      • Guest

        #4
        They are adjustable. On the CV carbs there is a small circular hole on top of the carbs right at the intake. They drill out very easily and under the caps is the idle mixture screws which may need new o-rings.

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        • Guest

          #5
          Also check fuel flow from the tank which is controlled by a pos 80 Suzuki petcock which is NOT one of their finest moments.

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          • Speed_Demon

            #6
            Originally posted by chef1366
            They are adjustable. On the CV carbs there is a small circular hole on top of the carbs right at the intake. They drill out very easily and under the caps is the idle mixture screws which may need new o-rings.

            http://www.cycleorings.com/
            Thats good to know. For now though I don't want to mess with any factory settings until I sort out the problem at hand.

            I'm going to go test the passages connecting the pilot to the main jet crcuit.

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            • spots25

              #7
              also, the low speed jet has little tiney holes, and they're probably plugged. I had the same problem on my interceptor, but I ran a 011 guitar string through it, and it cleared it right out

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