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petrol coming out of carb inlet (airbox - carb) connector

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    petrol coming out of carb inlet (airbox - carb) connector

    I have just rebuilt a wreck of a gsx 250 and it is now tuned pretty good and
    runs well.
    Plugs ok, Coils ok, HT leads ok, Valve clearances ok, Timing ok, mixture set to 1.5 turns out and
    is ok.
    HOWEVER:
    When i stop after running the engine for a few minutes on the RH carb petrol comes out it seems from the jet
    at the air inlet end mouth ?
    It starts coming out not immediately but after say 30 - 2 minutes.

    It stops in the end but i have to use a rag to wipe it up !

    What is this ?
    I have had the carbs to bits many times and they are cleaned.
    The tank is on when i do this.

    please help ......

    Jules.
    UKJULES
    ---------------------------------
    Owner of following bikes:
    1980 Suzuki GS550ET
    1977 Yamaha RD 250D
    1982 Kawasaki GPZ 750 R1
    1980 Suzuki GSX 250E

    #2
    Sticky float valve?
    1980 GS550ET

    Comment


      #3
      It only happens when it is turned off after running fine ?

      I have had the carbs to bits and the float valve does not seem to be sticking !
      they as clean as you can get. The same as the other one but that is fine.
      UKJULES
      ---------------------------------
      Owner of following bikes:
      1980 Suzuki GS550ET
      1977 Yamaha RD 250D
      1982 Kawasaki GPZ 750 R1
      1980 Suzuki GSX 250E

      Comment


        #4
        Originally posted by ukjules View Post
        It only happens when it is turned off after running fine ?
        You have a bad petcock valve or it's in the prime position.
        http://img633.imageshack.us/img633/811/douMvs.jpg
        1980 GS1000GT (Daily rider with a 1983 1100G engine)
        1998 Honda ST1100 (Daily long distance rider)
        1982 GS850GLZ (Daily rider when the weather is crap)

        Darn, with so many daily riders it's hard to decide which one to jump on next.;)

        JTGS850GL aka Julius

        GS Resource Greetings

        Comment


          #5
          I have yet to look at the petcock proper.
          So its strip down petcock - ill do that first.

          Just checked and it is coming out of both ! inlets.
          It is just that the lh one takes longer to start coming out ?
          It does not seem to stop either on the lh one - bike lent over to the left.

          It is not set to prime when this happens by the way.
          It is set to normal and not reserve
          Last edited by ukjules; 04-01-2016, 04:06 PM.
          UKJULES
          ---------------------------------
          Owner of following bikes:
          1980 Suzuki GS550ET
          1977 Yamaha RD 250D
          1982 Kawasaki GPZ 750 R1
          1980 Suzuki GSX 250E

          Comment


            #6
            Crap in the fuel? Thats a question, NOT a order. Worn float tip? Do you have a in line filter or at least those domed screens over ure needle jet? Also be carefull, flooded carb/airbox can also mean flooded combustion chamber. If you crank the engine over you run the risk of bending a conrod. Pull the spark plug out 1st before you start the engine after any flooding.

            Comment


              #7
              How would crap in the fuel cause leaking ?
              Float tip springy thing seems ok.

              Anyway i have cleaned the carbs twice now - stripped down completely and
              immediately the same thing happens - leaking only when stopped engine after a minute or so.
              the second time i stripped them down there was no filth in them.

              I have had to disconnect the tank from the carbs to stop the leak.

              the leak is not from the petcock but i will strip that down tomoorrow if thought should
              just to be sure all clean.
              UKJULES
              ---------------------------------
              Owner of following bikes:
              1980 Suzuki GS550ET
              1977 Yamaha RD 250D
              1982 Kawasaki GPZ 750 R1
              1980 Suzuki GSX 250E

              Comment


                #8
                Crap in the fuel means the float needle may not seat properly all the time. If your float needle is worn then again, it'll let fuel through when seated. It won't necessarily show when running as your bike is using the fuel that's coming through. Plus does the float needle seat sit in an o ring? That could be split and let fuel in.
                79 GS1000S
                79 GS1000S (another one)
                80 GSX750
                80 GS550
                80 CB650 cafe racer
                75 PC50 - the one with OHV and pedals...
                75 TS100 - being ridden (suicidally) by my father

                Comment


                  #9
                  Needle valve:
                  I took out both and cleaned them - they both seem fine work on the bench.

                  the carbs are almost identical to the diagram below (a gpz 750)


                  I will check again though:

                  Clean carbs and needle valve
                  check float height (this issue may have always happened as i have only just got it going)
                  Check over the petcock but i will have to check i have not done that already.

                  carb layout similar to this !.jpg
                  Last edited by ukjules; 04-01-2016, 05:24 PM.
                  UKJULES
                  ---------------------------------
                  Owner of following bikes:
                  1980 Suzuki GS550ET
                  1977 Yamaha RD 250D
                  1982 Kawasaki GPZ 750 R1
                  1980 Suzuki GSX 250E

                  Comment


                    #10
                    You have to inspect the needle valve with a magnifying glass. Tiny imperfections can let fuel through. plus if your carbs are the same as the diagram then you have that o ring. Check it's not split or perished.

                    You can do a bench test. Set the carbs up off the bike and fill with fuel down the fuel inlet hose. The hose should stay full for a good while (several minutes at least) - the needle valves are / should be very effective against letting excess fuel in to the float bowls.
                    79 GS1000S
                    79 GS1000S (another one)
                    80 GSX750
                    80 GS550
                    80 CB650 cafe racer
                    75 PC50 - the one with OHV and pedals...
                    75 TS100 - being ridden (suicidally) by my father

                    Comment


                      #11
                      i will check the needle valve more closely and the thing it sits in with the seal.
                      (It could be that this issue has always happened !)

                      I have only had it for a month or so and got it going. goes fine by the way but
                      it might have some juddering when gaining speed 40 - 60. Was thinking this was the atu ....
                      This is not for now though.

                      ill study the needle valve tomorrow

                      Surely it simply has to be the needle valve ?
                      or (like the other chap said) the petcock - but off the carbs that does not leak ?

                      thanks
                      Last edited by ukjules; 04-01-2016, 05:48 PM.
                      UKJULES
                      ---------------------------------
                      Owner of following bikes:
                      1980 Suzuki GS550ET
                      1977 Yamaha RD 250D
                      1982 Kawasaki GPZ 750 R1
                      1980 Suzuki GSX 250E

                      Comment


                        #12
                        Guys, you missing the point of a bad petcock. He may have floats not sealing properly, but no vacuum operated petcock should allow fuel to flow once the engine is off. Unless the petcock has been replaced with a simple ON/OFF shutoff valve, the one in there is bad.

                        Don't attempt to rebuild the one you have. I've tried several times as have many on here and the success rate is very poor. Replace the petcock with a new one and most of your problems will go away.
                        http://img633.imageshack.us/img633/811/douMvs.jpg
                        1980 GS1000GT (Daily rider with a 1983 1100G engine)
                        1998 Honda ST1100 (Daily long distance rider)
                        1982 GS850GLZ (Daily rider when the weather is crap)

                        Darn, with so many daily riders it's hard to decide which one to jump on next.;)

                        JTGS850GL aka Julius

                        GS Resource Greetings

                        Comment


                          #13
                          ok - the bike has been stood for ages and the petcock has not been touched.
                          So - I will do as you say and look at the petcock - first.

                          I will post pictures tomorrow - this is my hobby bike so not critical but i will
                          dismantle it as i have had recent success's with gpz750 and gpz600 petcocks.
                          if i bust it ill get another ... hopefully.

                          (but what about the tank not leaking when unattached to the carbs ?
                          ie petrol pipe and vacuum pipe off it and free of bike ?
                          does that mess up the theory ?
                          its late my brain has gone !

                          thanks - wil do this tomorrow
                          Last edited by ukjules; 04-01-2016, 06:14 PM.
                          UKJULES
                          ---------------------------------
                          Owner of following bikes:
                          1980 Suzuki GS550ET
                          1977 Yamaha RD 250D
                          1982 Kawasaki GPZ 750 R1
                          1980 Suzuki GSX 250E

                          Comment


                            #14
                            Ok testing today:

                            1) External tank with feed direct into carb fuel line
                            vacuum line free / prime of course shut off
                            bike runs and leaks out after after 8 mins after stopping engine but fuel able to flow.
                            I can feel the vacuum pulses on the vacuum line when engine running

                            2) removed petcock and dismantled.
                            Very clean and i had cleaned it a few weeks ago. However
                            when i blew out the vacuum (with my diving cylinder) nozzle some crap did come out .....
                            The way this is made - it would have allowed some air to come out but the passage was semi blocked.

                            3) petrol out of tank and now cleaned up - not much filth in the tank and all
                            caught by the filter in the tank. There was some around the base of the filter.

                            4) Not that it was leaking but the petcock / tank seal is now creased and i have to renew it
                            (It leaks now)
                            so can test no further with the tank on and vacuum.

                            petcock repair kit ordered but will only put on the tanks seal first.
                            (Might try some instant sealant just to test it as i want to know what is happening here
                            anfd if i need to dismantle the carb again !

                            P.S the petcock is on / res and a screw for prime
                            Last edited by ukjules; 04-02-2016, 12:26 PM.
                            UKJULES
                            ---------------------------------
                            Owner of following bikes:
                            1980 Suzuki GS550ET
                            1977 Yamaha RD 250D
                            1982 Kawasaki GPZ 750 R1
                            1980 Suzuki GSX 250E

                            Comment


                              #15
                              Carb repair kit ordered as the needle valve holders seal was perished.
                              It gave no seal and fell to bits at the first attempt to prize it out.

                              All else was clean as i had done this before but def missed the seal or indeed
                              ignored through inexperience the slackness of it !

                              float heights ok - at a quick masurement glance



                              GSX 250 carb seal worn.jpg
                              Last edited by ukjules; 04-02-2016, 12:27 PM.
                              UKJULES
                              ---------------------------------
                              Owner of following bikes:
                              1980 Suzuki GS550ET
                              1977 Yamaha RD 250D
                              1982 Kawasaki GPZ 750 R1
                              1980 Suzuki GSX 250E

                              Comment

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