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82 GS750 Won't run after engine is warmed up

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    82 GS750 Won't run after engine is warmed up

    Won't run after engine is warmed up

    Yesterday I took my 82 GS750 out for a ride, it performed great, the engine was powerful and smooth.
    But later in the evening after the engine cooled down I tried to start it and it only ran while the choke
    was on. Today I tried again and it won't idle, only runs with full choke and after the engine warms up it won't run at all.
    It has never acted like this before, I'm stumped.

    Any ideas??
    1982 Suzuki GS750E
    1979 Suzuki GS750E
    1978 Kawasaki KZ650 C2
    1977 HD CR1000
    1977 Kawasaki KZ400
    1974 Honda CB750

    #2
    The choke on Mikunis is actually a separate mini-carburetor integral and in parallel with the main carburetor body. It draws fuel from the float bowl and air from the bellmouth, but shares nothing else with the warm running carb fuel or air circuits If it runs on the choke but won't with the choke closed, means it's unlikely to be ignition/timing -at least when it's cold. Check for a spark when warm to make confirm it's not ignition.

    Will it run with the choke partially on when warm and die when you close the choke? If it does my suspicion would be a blockage in the idle/pilot circuits of one or more of the carbs. Does it just drop dead or is stumbling before it stops running. If it stumbles and it's a it's possibly one or two carbs blocked. If it dies possible that it's sediment could have blocked all the carbs if none of them is fueling.

    Post a video if you can.
    Last edited by KiwiAlfa156; 10-11-2021, 11:27 PM.
    sigpicDarryl from Kiwiland

    1982 GSX1100S Katana
    1982 GSX750S Katana
    1982 GS650G Katana

    Comment


      #3
      possibly a bad air leak from the manifolds that will get worse as rubber warms up?

      If it doesnt run at all though I'd be thinking about major things that effect all cylinders as I'd expect it to run on 2 albeit badly. Maybe check to see if you have enough gas flowing into the float bowls, (I had problems with starvation because of an elongated fuel hose)

      1982 GS550Ez, 1980 Yam RD350LC 4L0, 1980 Yam DT175,
      1977 Yam RD250D(Sold)
      London UK

      Comment


        #4
        not to be a nag, but if you browse the other threads, you might find some specific solutions to narrow your troubleshooting.
        Forum: GS Motorcycle Discussion Area

        This area is to be used only for general GS topics. For non-GS related topics, join the Off-Topic usergroup. Technical questions are not to be posted here.

        Comment


          #5
          Done, sorry for misplacing my question.
          1982 Suzuki GS750E
          1979 Suzuki GS750E
          1978 Kawasaki KZ650 C2
          1977 HD CR1000
          1977 Kawasaki KZ400
          1974 Honda CB750

          Comment


            #6
            Like every one above, it Definitely sounds like the carbs and if it won't run on three cylinders either, fuel supply seems suspect..kinked hose, dirty tank filter, petcock not opening, vaccum line to petcock iffy...stuff like that.

            Comment


              #7
              Plugged gas cap vent is a possibility, but my money is on dirty carbs.

              V
              Gustov
              80 GS 1100 LT, 83 1100 G "Scruffy"
              81 GS 1000 G
              79 GS 850 G
              81 GS 850 L
              83 GS 550 ES, 85 GS 550 ES
              80 GS 550 L
              86 450 Rebel, 70CL 70, Yamaha TTR125
              2002 Honda 919
              2004 Ural Gear up

              Comment


                #8
                So far I've learned the Petcock is flowing gas, but as I said before the engine will no run after it warms up. Cold it will run with chock on, but once heated up it will not. Darnest thing.
                1982 Suzuki GS750E
                1979 Suzuki GS750E
                1978 Kawasaki KZ650 C2
                1977 HD CR1000
                1977 Kawasaki KZ400
                1974 Honda CB750

                Comment


                  #9
                  Fuel starvation does seem likely, but I would also check ignition when warm as KiwiAlpha suggests. I've had outboard coils act up only when they got hot--if you run with the tank off, maybe check them for overheating then test them with an ohm meter.
                  1978 GS 750 E
                  1979 XS11 Standard
                  1973 CB450

                  Comment


                    #10
                    Problem solved.
                    It was a fuel starvation issue caused by a leaky vacuum line from Petcock.
                    Tip of hose was hard and leaked, simply clipped a 1/4 i nch off the tube and reinstalled.
                    Suzie purrs like a kitten now.
                    1982 Suzuki GS750E
                    1979 Suzuki GS750E
                    1978 Kawasaki KZ650 C2
                    1977 HD CR1000
                    1977 Kawasaki KZ400
                    1974 Honda CB750

                    Comment

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