1955 Johnson 5.5 hp converted to single fuel line with pump puking oil or carbon

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  • April 28, 2026 at 12:00 pm #316727
    DickS

      Seakaye12, This CD-12 is a replacement for my 7.5 HP Ted Williams (McCulloch) motor that I have not been able to get running…Marvel Shebler carb is the problem.  Actually I was trying to dial in the carb on the CD-12 after kit installed and new power shaft seal, prop seal and shift seal replaced.  I was having trouble keeping the motor running at low speed and noticed that the carb bowl was not completely full.  I guessed that the backflow preventer in the fuel line or the quick connector was failing.  I installed a new fuel line and found that the fuel in the bowl was full but I was still having an issue getting the low speed idle dialed in.  When I shut the motor down is when I noticed the oil/fuel puking out.  I am going to try to get to the lake to test out/dial in the motor this week when I have a chance to dial high speed at WOT, then adjust the low speed idle.

      April 28, 2026 at 12:13 pm #316729
      DickS

        Not dialed in and that was what I was trying to do when I saw the oil/gas puking out the exhaust and accumulating on the surface of the trash can filled with cooling water.  My main experience with 2-stroke are 1973 Chrysler 75 hp on my Center console serviced at marina, lawn mowers and chainsaws.  The motor does run but I have not been able to dial it in properly.

        April 28, 2026 at 12:18 pm #316730
        RICHARD A. WHITE
        Participant

          Lifetime Member

          Dial the low speed first, then high speed, The TN’s and TD’s are opposite of that..

          http://www.richardsoutboardtools.com
          classicomctools@gmail.com

          April 28, 2026 at 8:13 pm #316768
          JACQUES
          Participant

            cd-carb-bugs-1

            to start  and  idle fuel get sucked in via the upper idle drip chamber.  Fuel reaches it via a very narrow side channel  from the bowl to the top just beind the needle.    Thee LS needle allows fuel to reach the uper drip chamber and out 3 small holes while the throtlle plate is mostly closed at START  and cam follower sits in from og the mark on the cam.   check and recheck and blow out the side  channel make certain fuel does reach the top drip chamber   and  snug up the needle collar on the neelde packing.

            Joining AOMCI has priviledges 🙂

            April 29, 2026 at 7:19 am #316849
            Don
            Participant

              US Member

              It is difficult to convert the CD style powerheads to a single line system, there is no dedicated pressure port for the fuel pump, I usuallly recommend sticking with the two line pressure tank system on these engines.   Using the pressure outlet nipple on the intake manifold is tricky also, because you must make changes to the intake manifold/reed plate so you it will deliver pressure and vacuum pulses.

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