RDE-19 Compression numbers

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  • July 29, 2016 at 5:24 pm #4871
    johnyrude200
    Participant

      Had a customer bring one of these in, and truth be told, I have yet to work on one of these old beauties. Was just wondering what reasonable compression numbers are since this has the pressure relief valves on the cylinder head?

      I had 45/50 T/B hand cranking, and the motor has been sitting for at least 2-3 years unused. The rest of it is checking out for the usual repairs but I have the A-OK to fix the motor as needed to turn it back into a daily driver for a vintage boat piece.

      Even at 45/50, this thing is a bear to pull over and cranking speed was pretty slow despite my ‘strongest’ efforts to do it manually!

      July 29, 2016 at 5:28 pm #41187
      fleetwin
      Participant

        US Member - 2 Years

        I’m pretty sure that engine has a compression relief, so you will want to crank it electrically to get true compression readings.

        July 29, 2016 at 7:33 pm #41191
        Mumbles
        Participant

          I was getting 140 – 146ish on the ’56 RDE 18. Plugs out with leads grounded and spinning it with the electric starter.

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          July 29, 2016 at 8:04 pm #41192
          johnyrude200
          Participant

            Ill have to hook up the electric starter. It has the pressure relief valves on this one.

            July 29, 2016 at 8:44 pm #41194
            chris-p
            Participant

              They are a bear to get a good compression test on, especially on a stand. On an electric start, the starter is necessary to get an accurate reading. If the 50 psi is true, WAY too low for a Big Twin. Between 95 and 140 is what I typically find. 105 to 120 is the average.

              July 30, 2016 at 12:49 pm #41229
              opposedtwin
              Participant

                US Member - 2 Years

                I have checked literally dozens of them and own about 10. I have never had one over 125. Maybe my guage is a bit off. It does have a hose that’s about a foot long.
                Scott B

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