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  • J Pistons

    How far can a late 61" J cylinder be bored and where can pistons be found? Jerry

  • #2
    Great question Jerry. My front cylinder is rust pitted and I need pistons as well. I recall Matt Walksler stating on another forum that he used flathead Ford pistons in his 61". Does anyone know if Ford pistons are viable replacement?
    Eric Smith
    AMCA #886

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    • #3
      My rear is used at +.100" and the piston has no markings and I am not really familiar with J's. Front is used at standard.

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      • #4
        Think you can use UL Pistons or get higher compression pistons from Competition Distributing. Check the Yahoo harley j/jd group. There's a long post on using UL pistons. The J/JDs had a taper ground bore(tighter at the top than the bottom.). The cylinders need to be straight bored to use more modern pistons.
        David Morrill
        Sylacauga, AL. USA.
        AMCA #15284

        Deadly Dave's Blog
        Sharing the Lost Stories of Early American Motorcycling.

        http://dlmracing.blogspot.com/

        1921 Harley-Davidson Model J Racer

        It will break a hundred, if you drop it from a plane!

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        • #5
          David That stuff all works for JD but I do not think J. Competition has only 74" pistons on their website - no 61's. I am going to call them and see. Their pistons I think are made by Venolia.

          Jerry

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          • #6
            I use 214 cu in Bedford truck pistons.
            There is a Mitsubishi piston that a lot of guys use and it raises the com a bit.
            If you want to know exactly which Mitsi piston I'll have to ask around for details.
            Bedford pistons go straight in with no mods needed. Maybe there's a Chev equivilant as they are both GM products.
            Don't get too carried away with your overbore size as you wouldn't be the first person to end up with a detachable head cylinder.
            Peter Thomson, a.k.a. Tommo
            A.M.C.A. # 2777
            Palmerston North, New Zealand.

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            • #7
              flathead piston

              hey Jerry I may have a stash of n.o.s. flat head piston's at the old house, I will be stopping by later today and I will see whats left.

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              • #8
                Tommo
                I'd be interested in the part numbers of the Bedford truck piston as well as the Mits.
                Thanks
                Mark
                Mark Masa
                www.linkcycles.com

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                • #9
                  Mark
                  The Hepolite number for the Bedford pistons is 10171
                  As soon as I find out the Mitsi details I'll let you know.
                  Peter Thomson, a.k.a. Tommo
                  A.M.C.A. # 2777
                  Palmerston North, New Zealand.

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                  • #10
                    Tommo Have you found out anything more on the pistons. I tried searching for your numbers but could not really come up with much.

                    Jerry

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