Announcement

Collapse
No announcement yet.

Gas leaking out of one of the carb vent tubes. Doesn't look like any float issues.

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Gas leaking out of one of the carb vent tubes. Doesn't look like any float issues.

    Hey guys, looking for some advice on what to look for. This is for a 1982 Suzuki GS450L

    So one of my carb vent tubes is leaking a lot of gas when the bike is RUNNING. Only when running. So I don't think its a petcock issue.

    It also leaks a lot of gas when the petcock is set to PRIME.

    So my initial guess was a float issue. I opened up the float bowls, but nothing seems stuck, and the float needles seem fine. Also very clean. Also checked the needle jets, and no gunk.

    So I'm going to take apart the rest of the carb. What I want to know is, what should I be looking for? What else in the carb equation can cause fuel to be leaking?

    Also, the strange thing was this was not happening yesterday when I was turning the bike on. Just today. Prior to yesterday, it hasn't been turned on in a long time, as I wasn't able to work on it for half of last year. I'm wondering if something in the fuel tank gunked something in the carbs.

    Again, the float bowl itself was very clean.

    Pre emptive thanks to anyone who gives me some info or advice.

    #2
    has the petcock been overhauled ?
    Especially avoid the K&L set with yellow label.

    If it leaks a lot, hopefully the diagnose is easy.
    Better than a single drip once every fortnight i mean.

    Easiest and quickest check is to remove the vacuum line from
    the petcock and see if gas comes out of the petcock through this pipe.
    Try this with petcock on all 3 positions.

    Next, connect a hose to the vacuum pipe and suck on it.
    You should feel the vacuum system shut and close the connection.
    Mouth full of gas ? Try this with petcock on all 3 positions.

    Next remove the fuel line from the petcock and see if it leaks when set to
    normal/res.

    If no to these questions, the carbs are next in line to check.

    Old or dirty floats may stick, see if they move easily on their axis.
    Think you already did this and they are clean and move freely.

    Old float needles may stick now and again, sometimes just once in a while.
    This is hard to diagnose or reproduce, but is usually the cause of leaking.

    Hope this helps
    Last edited by Rijko; 04-23-2017, 05:11 PM.
    Rijk

    Top 10 Newbie Mistakes thread

    CV Carb rebuild tutorial
    VM Carb rebuild tutorial
    Bikecliff's website
    The Stator Papers

    "The thing about freedom - it's never free"

    Comment


      #3
      Hey Rijko, thanks for the response.

      Petcock all checks out. Works as needed. (tried everything you mentioned. No gas in mouth, just fumes :P)

      I'm fairly certain it is a carb issue.


      Now here is the weird thing.

      I went to turn the bike on today for more troubleshooting, and no gas is leaking out. Tried it again, and nothing is leaking out.

      I don't understand lol.

      So day 1 it went from no leaks, day 2 it was leaking like crazy from one of the carb vent tubes, day 3, no leaks.

      Comment


        #4
        i have the same issue with one of my bikes since last month.
        Only leaks sometimes, sometimes during driving, sometimes
        when moving the bike in the garage, sometimes just while parked.
        Sometimes a little p*ss stain on the floor, sometimes it will pour out
        like it needs to empty a full blatter like me after a bar visit
        Teaches you not to forget to take the petcock OFF prime though.
        Ask me how i know.

        Known issue, 99% it's old float needles and seats.
        Replacing those will solve the issue, i'm sure.
        Last edited by Rijko; 04-23-2017, 06:03 PM.
        Rijk

        Top 10 Newbie Mistakes thread

        CV Carb rebuild tutorial
        VM Carb rebuild tutorial
        Bikecliff's website
        The Stator Papers

        "The thing about freedom - it's never free"

        Comment


          #5
          Your bike is 35 years old. Go through the carbs and make sure everything is right. Replace all the O-rings since they are sure to be hard and deteriorated. Basscliff's website has a 450 specific carb rebuild tutorial.

          And check the Newbie Mistakes thread linked in my signature to see if there is anything else you should be tending too like adjusting the valves. Maintenance is the way forward and the best way to assure your bike is reliable.
          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


            #6
            Originally posted by Nessism View Post
            Your bike is 35 years old. Go through the carbs and make sure everything is right. Replace all the O-rings since they are sure to be hard and deteriorated. Basscliff's website has a 450 specific carb rebuild tutorial.

            And check the Newbie Mistakes thread linked in my signature to see if there is anything else you should be tending too like adjusting the valves. Maintenance is the way forward and the best way to assure your bike is reliable.
            Sorry if I misrepresented this the wrong way, but I didn't just start working on the bike. I started last year.
            All the O-Rings are already replaced, and the Carbs are cleaned.
            Valves are already adjusted (although there is one that needs a shim closer to optimal)

            This is a new issue.

            Comment


              #7
              Originally posted by Rijko View Post
              i have the same issue with one of my bikes since last month.
              Only leaks sometimes, sometimes during driving, sometimes
              when moving the bike in the garage, sometimes just while parked.
              Sometimes a little p*ss stain on the floor, sometimes it will pour out
              like it needs to empty a full blatter like me after a bar visit
              Teaches you not to forget to take the petcock OFF prime though.
              Ask me how i know.

              Known issue, 99% it's old float needles and seats.
              Replacing those will solve the issue, i'm sure.
              What is the float seat exactly?

              Like I said, I checked my needles and they seem fine. Do you know what the characteristics of a good one is, or how can I tell if one is bad?

              Comment


                #8
                There is an o ring under each of the float valve seats - if they are split or pinched it will pass fuel through straight into the carb bowl bypassing the float valve.

                The thing that the screw is holding in is the float valve seat:

                Current:
                Z1300A5 Locomotive (swapped my Intruder for it), GS450 Cafe Project (might never finish it....), XT500 Commuter (I know - it's a Yamaha )

                Past:
                VL1500 Intruder (swapped for Z1300), ZX9R Streetfighter (lets face it - too fast....), 1984 GSX750EF, 1984 GSX1100EF (AKA GS1150)
                And a bunch of other crap Yamahas....

                Comment


                  #9
                  Originally posted by lettuceman44 View Post
                  What is the float seat exactly?

                  Like I said, I checked my needles and they seem fine. Do you know what the characteristics of a good one is, or how can I tell if one is bad?

                  like Hillsy said .... the o-ring is important too.

                  here's another pic, the copper part is the seat.
                  Yours may look a little different but you get the idea.
                  Since GSR only allows 1 pic per post i will have to post more than 1 answer

                  mikuni-needle-valve-with-viton-tip-for-spigot-flange-mount-carburetors.jpg
                  Last edited by Rijko; 04-23-2017, 07:45 PM.
                  Rijk

                  Top 10 Newbie Mistakes thread

                  CV Carb rebuild tutorial
                  VM Carb rebuild tutorial
                  Bikecliff's website
                  The Stator Papers

                  "The thing about freedom - it's never free"

                  Comment


                    #10
                    sometimes you can see wear on the needle

                    wornneedle.jpg
                    Rijk

                    Top 10 Newbie Mistakes thread

                    CV Carb rebuild tutorial
                    VM Carb rebuild tutorial
                    Bikecliff's website
                    The Stator Papers

                    "The thing about freedom - it's never free"

                    Comment


                      #11
                      10.jpg

                      sometimes the needle point has little visible wear, but sticks to the copper
                      seat on the long side of the needle, not the tip.

                      The issue is worse with bio-ethanol added to the fuel, leaning the mixture
                      and creating more friction between needle and seat

                      I have always had succes with this issue by replacing the needles
                      and seat as a pair.
                      Rijk

                      Top 10 Newbie Mistakes thread

                      CV Carb rebuild tutorial
                      VM Carb rebuild tutorial
                      Bikecliff's website
                      The Stator Papers

                      "The thing about freedom - it's never free"

                      Comment


                        #12
                        From memory all the GS float valve seats are press in (not screw in). Be careful pulling them out as you can easily distort / fubar the seat where the valve enters. If you squeeze them out of round the valves can stick. A squirt of WD40 or similar will help loosen the o ring.

                        Anyway, drain the carbs, take them off, take off the bowls, hold the carbs upside down, get a longer piece of fuel hose on there and blow into it. If the valves or seats are leaking you will be able to blow air through them and hear where it is leaking from.

                        ALWAYS bench test your carbs for leaks before you put them back on.
                        Current:
                        Z1300A5 Locomotive (swapped my Intruder for it), GS450 Cafe Project (might never finish it....), XT500 Commuter (I know - it's a Yamaha )

                        Past:
                        VL1500 Intruder (swapped for Z1300), ZX9R Streetfighter (lets face it - too fast....), 1984 GSX750EF, 1984 GSX1100EF (AKA GS1150)
                        And a bunch of other crap Yamahas....

                        Comment


                          #13
                          Originally posted by hillsy View Post
                          From memory all the GS float valve seats are press in (not screw in).

                          the CV series has the pressed seats, the VM series are the screwed type afaik.
                          VM 26mm, 27mm, 28mm, 29mm have them

                          If you're lucky, you can find transparent float bowls and see what's going on

                          s-l1600.jpg


                          sometimes the needles have a bit of damage on the sides and
                          polishing that away solves the issue
                          Last edited by Rijko; 04-23-2017, 08:15 PM.
                          Rijk

                          Top 10 Newbie Mistakes thread

                          CV Carb rebuild tutorial
                          VM Carb rebuild tutorial
                          Bikecliff's website
                          The Stator Papers

                          "The thing about freedom - it's never free"

                          Comment


                            #14
                            VM26 with screw in seats here. I forgot to tighten a valve seat and that (obviously) led to a leaky carb.

                            A clear bowl is brilliant!
                            Last edited by hannibal; 04-23-2017, 10:16 PM.
                            Jordan

                            1977 Suzuki GS750 (My first bike)
                            2000 Kawasaki ZRX1100
                            1973 BMW R75/5

                            Comment


                              #15
                              Thanks for the help guys. I'll take a look at these suggestions, and check the o rings to be sure.

                              Comment

                              Working...
                              X