RDE-19 Compression numbers

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  • johnyrude200


    Replies: 782
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    #4871

    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!


    fleetwin

    US Member - 2 Years
    Replies: 4737
    Topics: 46
    #41187

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


    Mumbles


    Replies: 5764
    Topics: 298
    #41191

    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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    johnyrude200


    Replies: 782
    Topics: 186
    #41192

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


    chris-p


    Replies: 2456
    Topics: 153
    #41194

    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.


    opposedtwin

    US Member - 2 Years
    Replies: 968
    Topics: 259
    #41229

    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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