Cylinder Overboring - R90S Add'l Question

Discussion in 'Old's Cool' started by hank0614, Jan 12, 2011.

  1. hank0614

    hank0614 TurtleGuy

    Joined:
    Dec 10, 2006
    Oddometer:
    15
    Location:
    In the Adirondack Park, New York USA
    Thanks for all the replies. My friend has one question: where is the spigot measured to determine whether it is a small 97mm or a large 99mm spigot? Is it at the base or the largest point where it enters the engine case? As the bike was built in 10/75 he may be at the point of change over where BMW was using up what small spigot cylinders were left in inventory.

    Thanks again!

    Hank
    '72 R60
    '95 K75S



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    #1
  2. wirewrkr

    wirewrkr the thread-killer

    Joined:
    May 23, 2008
    Oddometer:
    4,295
    Location:
    HIGH desert
    As I mentioned before, if it is a 10/75 production, it should be the large spigot.
    I also mentioned that the diameter of the pushrod tubes is also a determining factor.
    The 18 mm diameter is for the large spigot, the 16 is for the small spigot.
    Pretty easy to tell.
    16mm is close to 5/8"
    #2