1957 Johnson 35hp Carb problem low speed plug

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  • July 20, 2015 at 12:42 am #2055
    vintin
    Participant

      On the low speed adjustment the insert plug looking part that goes into the carb came out with the packing nut and needle. I’ve had this happen in the past but have just put the parts back in and the motor had run fine for a couple of years now. I was replacing packing washers a few days ago and want to get it fixed right this time.

      How do I get this plug to stay in the carb?

      Locktite blue? Red?

      Advice please!

      Thanks.

      July 20, 2015 at 12:51 am #20430
      gjonz
      Participant

        I believe it is supposed to pull out for cleaning. The packing and packing nut keep it from turning or pulling out if the nut is cinched down properly.

        Greg

        July 20, 2015 at 1:58 am #20434
        chris-p
        Participant

          Yup it is supposed to come out. Tightn nut to keep it from free spinning while you adjust needle

          July 20, 2015 at 11:52 am #20452
          george-emmanuel
          Participant

            US Member

            Use a screwdriver shaped specifically for the width of the opening and for the slot in the seat otherwise the seat can be distorted, which leads to galling threads and inability to remove it in the future. I shape my screwdrivers on a bench grinder and then fine tune them with a file. Make sure the edge of the screwdriver has a good snug fit into the slot of the seat. If the outside edge of the seat has "expanded" due to improper screwdriver, I use the file to carefully clean up the distortion.

            July 20, 2015 at 12:54 pm #20456
            vintin
            Participant

              Thanks for the tips guys. Sounds like I ‘fixed’ it already and didn’t know it! 🙂 And here I thought I had a carb problem. Feels good to get confirmation.

              George I think you may be talking about the float needle seating, which is something other than what I was asking about. Do appreciate it though.

              On a related note I’ve starting using 3/8 X 1/4 ‘O’ rings instead of packing washers. Feedback and other tips welcome.

              Dan

              July 20, 2015 at 8:17 pm #20480
              chris-p
              Participant

                Dan I cut my own packing washers out of cork gasket material from Canadian Tire or Princess Auto.

                A couple correct sized gasket punches make quick work of the OD and ID.

                July 20, 2015 at 10:10 pm #20487
                chris-p
                Participant

                  Also, those darn things ONLY come out when you don’t want them to.

                  I lost one tonight cleaning a carb. Gone into the nether regions under the work bench somewhere.

                  Went into a box of spare carbs, you think ANY of them want to come out. Nope.

                  July 20, 2015 at 11:12 pm #20490
                  george-emmanuel
                  Participant

                    US Member

                    Nope, I was talking about the high and low speed seats. I don’t have the ability to post factory pictures and that prevents me from having a good presentation.

                    On a carb, there generally is a threaded opening into the carb body for the high and low speed circuits. Into that opening a seat (what you called an "insert plug", is screwed into and it usually is brass and soft. That seat has a slot cut into it so a screwdriver can screw the seat into that opening. It is that slot I was referring to that needs a properly fitted screwdriver elsewise the slot of the seat will be damaged.

                    In your case apparently that "insert plug" (seat) was not screwed into the carb body snugly. If it was, it would not back out.

                    July 21, 2015 at 12:11 am #20498
                    vintin
                    Participant

                      Thanks George. Now you have me wondering. I didn’t see any threads on the plug that came out. I also need to work on the ability to post pictures.

                      July 21, 2015 at 12:35 am #20500
                      gjonz
                      Participant

                        Respectfully disagreeing with George on this. I don’t believe the OMC Big Twin carbs of this vintage have removable high/low speed seats. If the seat gets damaged, the carb body must be replaced as they are cast into the carb body.

                        The insert the OP referred to is simply an aluminum tube that is threaded inside for the low speed needle. The packing and packing nut holds everything tight as described.

                        There is a brass jet inside the bowl that can be dicey getting them out. And also the float needle seat can be iffy with the wrong screw driver.

                        I have seen carbs with what George is describing, but the 50’s OMC’s do not typically have that design.

                        Greg

                        Greg

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