Cylinder Overboring - R90S Add'l Question

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

  1. hank0614

    hank0614 TurtleGuy

    Dec 10, 2006
    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!

    '72 R60
    '95 K75S

    <DL id=profile15786 class=postprofile><DT>hank0614 <DD><DD>Posts: 7<DD>Joined: Fri Aug 13, 2010 7:05 am<DD>
  2. wirewrkr

    wirewrkr the thread-killer

    May 23, 2008
    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"