Home Forum Ask A Member Help Please on Lightwin Carb issue?

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  • #1647
    seakaye12
    Participant

      US Member

      I have a 1964 Lightwin Evinrude that I have been having an on-going "hard-time" to get to run well. It’s got 75/80 PSI, all new ignition and a completely gone thru carburetor. New float; all the kit components (boss gasket) etc have been replaced. More than once lol….

      What am I missing?

      It runs "ok" ….but not the way it should. The rpm’s vary up and down…and it is NOT dropping a cylinder. It won’t idle down like it should. It seems to sometimes run rich…and other times it seems to run lean.

      If I hadn’t already replaced the float and needle/seat…..I would suspect that the fuel level in the bowl varies…..but I check and re-check things related to that…and find everything ok. Obviously I am missing something.

      Any hints?

      Chuck

      PS: The carburetor that is on it has the low speed and high speed needles. I know it shouldn’t have that on a 64….. but I can’t see any reason that it would make things worse. If anything…it should make them better?

      #17297
      chris-p
      Participant

        I guess the first question is, what carb is on it exactly?

        #17298
        seakaye12
        Participant

          US Member

          It has the original 1964 carburetor but the bowl half was swapped with one from a 1957 3 HP. That’s why it has the two needles.

          I originally ran it with the original bowl (fixed jet) and it ran the same with that one. I assumed (perhaps incorrectly) that the fixed jet had been messed up due to improper cleaning which might have enlarged it…

          #17303
          chris-p
          Participant

            I wonder if the surging is an air leak.

            Check the carb welch plugs, the throttle shaft, the crank seams, things like that?

            #17308
            fleetwin
            Participant

              US Member - 2 Years

              Nozzle gasket OK? Did it run the same way with the original bowl/fixed high speed jet?

              #17311
              seakaye12
              Participant

                US Member

                I can see no discernible play at the throttle shaft. At one point I dabbed heavy grease around the crankcase joint…no change. The nozzle (boss) gasket is new; the genuine OMC version that comes in the kit 439071.

                It did run the same way with the original bowl; I was sooooo sure that replacing the lower half would solve the problem.

                I did swap the entire carb with another one…and that made a huge difference…..so I feel that the issue is definitely in the carb somewhere.

                PS: It also starts hard. Sometimes requires the choke even when warm; other times it seems essentially flooded.

                #17342
                The Boat House
                Participant

                  Was removing this plug to clean these
                  passages part of your carb rebuild?
                  Should be a new one in you rebuild kit.

                  #17346
                  kevinrude
                  Participant

                    check the throttle cam follower — they sometimes get stuck in the full advance position when you throttle down — grease it up good and make sure that the spring actually pulls the thing back when throttling down

                    #17349
                    chinewalker
                    Participant

                      US Member

                      Is the screen between the air horn and the carb mouth? It was explained to me by a 40-year OMC tech that it needs to be there to run properly as it creates a rich condition akin to partial choke.

                      #17360
                      seakaye12
                      Participant

                        US Member

                        Yes I did pull the welch plug when I rebuilt. And; the screen is there.

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