1966 3 hp lightwin Carb problem

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  • September 15, 2016 at 3:44 pm #5262
    mercuryman
    Participant

      I have a 1966 lightwin 3 hp with the fixed jet , main jet. The motor is hard to start then will die after running a few seconds. Acts like running lean. Tried every thing no help, then I switched carb bowl for one with adjustable main jet. Now it runs perfect. Why is this happening has gas changed over the years. Also over the years I have had two 66 lightwins and both had slung a rod, have they been too lean all the time. Has anyone drilled out the high speed jet ?

      September 15, 2016 at 3:58 pm #44075
      lindy46
      Participant

        Fixed jet most likely clogged.

        September 15, 2016 at 4:08 pm #44078
        fisherman6
        Participant

          US Member
          quote lindy46:

          Fixed jet most likely clogged.

          The main jet orifice is a mere 0.029" in diameter and it clogs pretty easily. Also, even if the hole is open, if there is crud built up behind the hole inside the counterbored area it will still impede flow. The orifice plug should be removed and carefully cleaned. It takes a special tool or a carefully modified screwdriver to reach into the slot to remove it.

          That said, I have a ’66 JW that I replaced the old crudded up orifice with a brand new one. It still does not run like it should and I need to remove the carb again and give it a chemical dip and blow it out with aerosol and compressed air to try to clear it out. The passages are.very small in these carbs and clog up pretty readily if fuel is left in them.
          -Ben

          OldJohnnyRude on YouTube

          September 15, 2016 at 4:33 pm #44081
          frankr
          Participant
            quote mercuryman:

            I have a 1966 lightwin 3 hp with the fixed jet , main jet. The motor is hard to start then will die after running a few seconds. Acts like running lean. Tried every thing no help, then I switched carb bowl for one with adjustable main jet. Now it runs perfect. Why is this happening has gas changed over the years. Also over the years I have had two 66 lightwins and both had slung a rod, have they been too lean all the time. Has anyone drilled out the high speed jet ?

            Drilling it out is probably the best way to ruin the orifice.

            September 15, 2016 at 6:12 pm #44088
            mercuryman
            Participant

              When I started working on Lightwin with a light could see through the Jet. And with your info I tried pushing a .028 wire in jet and no fit.
              I soaked in Chem dip blew it out tried the wire again and it fit. Put bowl back and motor starts and runs fine in 5 minute test. Its great to have the experience of many outboarders to help.

              September 15, 2016 at 6:12 pm #44089
              cajuncook1
              Participant


                Those fix high speed jet removal tools are expensive ($30 to $35) and cheaply made. I purchased one 3years ago and it broke at the tip the first time I used it. Never got my money back.

                Frank, suggested I get this screw driver bit and it works great. It is just the right size and best of all it is cheap to purchase several of them. I ordered this from McMaster.com. You could also try a hardware store or online hardware store.

                I used it on all my OMC fixed high speed carburetors from the 1960’s to 1970’s. Remove it and soak it well and use air pressure to blow it out. Doesn’t take a lot of scratching around the office with a wire or drill bit to screw them up. Remember they are metered and the opening is smooth. If you clean it out with a drill bit or wire, you run the risk of enlarging the hole and also causing scrapes or imperfections. That will allow a rich running condition and allow oil to adhere to and gum up your high speed orifice even easier.

                Extra Clearance Slotted insert Bit.

                1/4" Hex Shank, 3/16" tip width, 1 1/2" length

                September 15, 2016 at 7:18 pm #44098
                mercuryman
                Participant

                  Thanks CC

                  September 16, 2016 at 12:21 am #44119
                  fleetwin
                  Participant

                    US Member

                    Using a small pipe cleaner soaked in engine tuner/carb cleaner usually gets that hard to see film that coats the walls of the jets….

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