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  • Gas leaking from carbs

    I've been updating my intro post with progress on my bike here:

    https://xs11.club/forum/idle-talk-fo...xs1100-special

    I've run into a problem with gas leaking from my airbox, so I've pulled the carbs for the 3rd time 😬👍 in just a couple of weeks (I'm getting good at it). I checked float heights and they look good. #1 and #4 are a little strong at 23.5 mm (see pic), #2 and #3 are dead nuts. Measurements taken with gasket removed, on the nature flat part next to little ridge.

    I decided I want to see how much gas is actually in each bowl so I hooked up my hanging gas tank with the carbs off the bike to see what happens. Gas leaked out of #2 carb, and possibly the air inlet - the hole at 4 o'clock position (see pic).

    I also recorded the amount of gas in each bowl by draining them each into a jar and marking their levels. The pic shows them to be pretty even, but #2 does have a bit more, which is weird because it's measurement was the same as #3. I emptied it each time into a measuring cup to see the grand total, which was around 280ml. Is there a target amount I should see?

    Any suggestions on what to do next?
    Last edited by TheNannerpus; 10-11-2021, 07:09 PM.
    Started riding in Sept. 2019

    1983 Honda CB650 Nighthawk (sold)
    2009 Suzuki GS500 (sold)

    2019 Suzuki SV650
    1993 Honda Nighthawk 750
    1980 Yamaha XS1100 Special (project)

  • #2
    This procedure in the link works the best

    http://www.xs11.com/xs11-info/tech-t...balancing.html

    1980 XS1100G "Dolly G" Full Dresser (with a coat of many colors )
    1979 XS1100SF (stock-euro mods planned)
    1984 XV700L Virago (to be hot-modded)
    1983 XJ750MK Midnight Maxim (semi-restored DD)
    1977 XS650D ( patiently awaiting resto)

    Sometimes it takes a whole tank of gas before you can think straight.

    Comment


    • #3
      Are you checking BOTH floats on each carb? All 8 floats should be EXACT in the measurement. If one carb is leaking, that is the one you need to look at! Check or replace the "O' rings on the valve seats if you have not already. Also, you can mount the carbs upside down in a vice, hook up the lines and verify that no gas will get past the needle/seat. Do NOT set the remote tank more than about 12" above the carbs for this test. If you have a bad casting, it should show up as gas weeping from someplace between the inlet and the seat.
      Ray Matteis
      KE6NHG
      XS1100 E '78 (winter project)
      XS1100 SF Bob Jones worked on it!

      Comment


      • #4
        Originally posted by Schming View Post
        This procedure in the link works the best

        http://www.xs11.com/xs11-info/tech-t...balancing.html
        Thanks for responding. I've come across this article in my research on this site. IMHO, what this article does not do is address its own goal: "accurate and sufficient fuel level in the float bowl."

        What is the correct level of fuel in the bowl? That's a target I can def hit adjusting the floats. And that's why I included the pics showing gas levels and total amount of gas. If I were told "each bowl needs 75ml of gas" then I'm off to the races. Right now, I'm adjusting to avoid a fuel leak and I'm not sure that's going to give me the best outcome.
        Started riding in Sept. 2019

        1983 Honda CB650 Nighthawk (sold)
        2009 Suzuki GS500 (sold)

        2019 Suzuki SV650
        1993 Honda Nighthawk 750
        1980 Yamaha XS1100 Special (project)

        Comment


        • #5
          Originally posted by DiverRay View Post
          Are you checking BOTH floats on each carb? All 8 floats should be EXACT in the measurement. If one carb is leaking, that is the one you need to look at! Check or replace the "O' rings on the valve seats if you have not already. Also, you can mount the carbs upside down in a vice, hook up the lines and verify that no gas will get past the needle/seat. Do NOT set the remote tank more than about 12" above the carbs for this test. If you have a bad casting, it should show up as gas weeping from someplace between the inlet and the seat.
          DiverRay

          On these leaking ones, I am checking both sides of the float. They measure the same. I have replaced all parts using the kits recommended here (from georgefix on ebay), I think they're T&L if I recall, made in Japan.

          The info that caught my eye was the height of my remote tank. I'm hanging it near the top of a 6' stepladder. Is that creating to much fuel pressure, and forcing gas out of the bowls?

          As asked in my above response, what should the fuel height be in each bowl? I can connect hoses to the drains and see where that comes out, but I don't know the target.
          Started riding in Sept. 2019

          1983 Honda CB650 Nighthawk (sold)
          2009 Suzuki GS500 (sold)

          2019 Suzuki SV650
          1993 Honda Nighthawk 750
          1980 Yamaha XS1100 Special (project)

          Comment


          • #6
            what should the fuel height be in each bowl?
            For the 81-82's, should be the same for 80's with the plastic floats.

            Click image for larger version  Name:	81 fuel level.png Views:	0 Size:	47.1 KB ID:	866791
            Last edited by bikerphil; 10-12-2021, 02:47 PM.
            2H7 (79)
            3H3

            Comment


            • #7
              Here's what I ended up doing.

              Based on research here and other places, the most important measurement seems to be fuel level in the bowl rather than float height. 23.5mm is where I set all the floats, which is only .5mm strong, and it did stop the fuel leak. And now I can put down the fire extinguisher when I start it up. (Though it's still close by.)

              The carb is back on the bike. I used my new carbtune to synch them, worked like a charm and evened out the idle (I'll add a video to my main thread).

              I'll use bikerphil (thanks!) info to check levels while carbs are on the bike. Is that data good for '80 Special? Nevermind, I see you updated the post - thanks!
              Last edited by TheNannerpus; 10-13-2021, 10:36 AM.
              Started riding in Sept. 2019

              1983 Honda CB650 Nighthawk (sold)
              2009 Suzuki GS500 (sold)

              2019 Suzuki SV650
              1993 Honda Nighthawk 750
              1980 Yamaha XS1100 Special (project)

              Comment

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