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  1. #1
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    Default Triumph with 76-Degree Offset, Stroker Billet Crankshaft

    Anyone have any experience with a MAP 76-Degree Offset, Stroker Billet Crankshaft in a unit-construction Triumph?

    According to the MAP website, " The 76-degree crankshaft allows one piston to be at top dead center while the other piston is just reaching it's maximum velocity. This offers the smoothest possible motion in the crank and eliminates much of the vibration in the Triumph twin."
    and
    it fits:
    "All Triumph 650-750cc Twins built after June 1971 (GE27209) though 1983 with metric timing side main bearing. Can be adapted to earlier 650cc twins (see below)"

    Specifications:

    89mm stroke
    1-3/4" journal (use with Norton Rod Bearings)
    Approximately 22 pounds

    See more here: http://www.mapcycle.com/performance-...ee-offset.html


    Stock unit-construction 650 / 750 stroke is 82 mm, so this a 7 mm longer stroke.

    Using the engine displacement calculator (http://www.revetec.com/Calculators/E...ulator-2.htm):

    71mm x 82mm = 649.3 cc (stock 650)
    71mm x 89mm = 704.7cc

    76mm x 82mm = 744cc (stock 750)
    76mm x 89mm = 807.5cc

    It's interesting, but definitely not cheap at $1,950.00 + Rods at $450 + cams at $450 + ignition at $350

    Anyone have experience with other stroker cranks in a unit-construction Triumph?
    Last edited by TriNortchopz; 01-12-2018 at 10:30 PM. Reason: capitalize Triumph

  2. #2
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    Default

    I wonder how many they sell at that price? Lol
    Gotta get/cut cams to match...
    Does the longer stroke necessitate new pistons or just clearances?
    Compression considerations?


    The XS650 crowd seem to phase their cranks more often .
    "Easier" for them. Due to crank and cam contruction.
    But the energy return and vibration factors are parallel
    And the feedback I've read is all positive...

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