Gas Leak

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  • mcycle-nut
    Forum Guru
    Charter Member
    Past Site Supporter
    • May 2002
    • 8382
    • Victoria, British Columbia, CANADA

    #1

    Gas Leak

    Ok, my '78 GS750 has become stinkor. It leaks gas, not puddles, but enough to stink up the garage and house. New float bowl gaskets, o-rings, and yellow teflon tape around the fuel tubes have been installed. Petcock is good. The carbs are wet just on top of the float bowls, and when I pull the carbs, they're wet inside the filters, and carb boots. Upon dismantling, I found gas between the large plate that the carbs mount to and the carbs. I'm thinking needles and seats. Anyone?
    Kevin
    E-Bay: gsmcyclenut
    "Communism doesn't work because people like to own stuff." Frank Zappa

    1978 GS750(x2 "projects"), 1983 GS1100ED (slowly becoming a parts bike), 1982 GS1100EZ,
    Now joined the 21st century, 2013 Yamaha XTZ1200 Super Tenere.
  • mortation

    #2
    Make sure your float needles are not stuck. They should be springy. Make sure your float height is correct. Those things with a good petcock should not allow any gas to leak.

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    • mcycle-nut
      Forum Guru
      Charter Member
      Past Site Supporter
      • May 2002
      • 8382
      • Victoria, British Columbia, CANADA

      #3
      Originally posted by mortation
      Make sure your float needles are not stuck. They should be springy. Make sure your float height is correct. Those things with a good petcock should not allow any gas to leak.
      They're not, and they are. Float height is correct. Floats even float! I think I am starting to answer my own question here. I figure when the bike gets shut off, the residual fuel between the petcock and the carbs is getting by the worn needles and seats, overflowing the bowls, causing wetness and stink. Am I on the right track?
      Kevin
      E-Bay: gsmcyclenut
      "Communism doesn't work because people like to own stuff." Frank Zappa

      1978 GS750(x2 "projects"), 1983 GS1100ED (slowly becoming a parts bike), 1982 GS1100EZ,
      Now joined the 21st century, 2013 Yamaha XTZ1200 Super Tenere.

      Comment

      • TallBoy

        #4
        i have an 81 gs850 and i was leaking gas out of the boots between my airbox and my carbs on the left side. i disassembled and reassembled and jumped up and down to no avail. then i started parking it on its center stand only, problem solved. also, try disengaging the gas line and the vacuum hose from the petcock to the carb, block the air from sucking in the tube and run the carbs out of gas. might blow something thrown or fix a sticking float.

        Comment

        • earlfor
          Forum LongTimer
          Charter Member
          GSResource Superstar
          Past Site Supporter
          • May 2002
          • 42413
          • off grid cabin 1/24/26 7pm

          #5
          Kevin, your petcock is faulty. Fuel must come from the gas tank and flow through the petcock before it gets to a carb. It wouldnt matter if you didnt connect the fuel line to the carbs and left it hanging and open, or left the floats and needles completely out. If the petcock was shutting off fuel flow when no vacuum (engine not running) was present, no fuel could flow. Time for a new petcock ol chap. :-)

          You MAY have seeping float needle seats too, but fer sure, the petcock is trashed.

          Earl
          Last edited by earlfor; 08-25-2007, 09:47 PM.
          Komorebi-The light filtering through the trees.

          I would rather sit on a pumpkin and have it all to myself than be crowded on a velvet cushion. H.D.T.

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          • mcycle-nut
            Forum Guru
            Charter Member
            Past Site Supporter
            • May 2002
            • 8382
            • Victoria, British Columbia, CANADA

            #6
            Originally posted by earlfor
            Kevin, your petcock is faulty. Fuel must come from the gas tank and flow through the petcock before it gets to a carb. It wouldnt matter if you didnt connect the fuel line to the carbs and left it hanging and open, or left the floats and needles completely out. If the petcock was shutting off fuel flow when no vacuum (engine not running) was present, no fuel could flow. Time for a new petcock ol chap. :-)

            You MAY have seeping float needle seats too, but fer sure, the petcock is trashed.

            Earl
            I was thinking petcock a while ago too, but the tank NEVER leaks when it's off the bike. That has me perplexed. I'm thinking the fuel that's in the line from the petcock to the carbs is overflowing the bowls when I shut off the bike, making the carbs just slightly wet. Otherwise, I would have puddles under the bike and hydrolock the cylinders, no?
            Kevin
            E-Bay: gsmcyclenut
            "Communism doesn't work because people like to own stuff." Frank Zappa

            1978 GS750(x2 "projects"), 1983 GS1100ED (slowly becoming a parts bike), 1982 GS1100EZ,
            Now joined the 21st century, 2013 Yamaha XTZ1200 Super Tenere.

            Comment

            • earlfor
              Forum LongTimer
              Charter Member
              GSResource Superstar
              Past Site Supporter
              • May 2002
              • 42413
              • off grid cabin 1/24/26 7pm

              #7
              OK then. I would be inclined after parking the bike for the night, to remove the fuel line from the petcock and fit a length of spare fuel line onto the petcock with the open end draining into jar. Take a lookie whats in the jar in the morning.

              Earl


              Originally posted by mcycle-nut
              I was thinking petcock a while ago too, but the tank NEVER leaks when it's off the bike. That has me perplexed. I'm thinking the fuel that's in the line from the petcock to the carbs is overflowing the bowls when I shut off the bike, making the carbs just slightly wet. Otherwise, I would have puddles under the bike and hydrolock the cylinders, no?
              Komorebi-The light filtering through the trees.

              I would rather sit on a pumpkin and have it all to myself than be crowded on a velvet cushion. H.D.T.

              Comment

              • doggscube

                #8
                Seal the jar with a shop rag to keep the gas from evaporating.

                Jeff

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