R1150GS MAHLE piston dimensions, weight categories and marking

Discussion in 'GS Boxers' started by palciatko, Oct 24, 2012.

  1. palciatko

    palciatko n00b

    Nov 30, 2009
    Hi there

    I need to order new left complete piston for my GS. :baldy According to manual and realoem, there are only one size category currently, marked as AB (AntiBluesmoke :D).

    But there are two weight categories - "+" and "-" :huh

    11 25 7 652 663 PISTON, ANTI-BLUESMOKE - AB+584-594GR
    11 25 7 652 664 PISTON, ANTI-BLUESMOKE - AB-574-584GR

    My old complete piston weights 585.3g, so it seems it is "+" weight category.
    What does circled mark mean? Does it mean weight category?
    Under circle, there is "101L37" mark (maybe piston diameter and height)


  2. def

    def Ginger th wonder dog

    Feb 28, 2004
    The woods and mountains of Alabama
    Hello Pal,

    Sorry, I cannot help with the piston weight selection (there are others here that are much smarter than I that will help) but, I am curious....why are you fitting one new piston? Why are you fitting a new piston at all? Is there some wear or damage we cannot see in your photo?

    Also, I see evidence of lots of varnish on the underside of the piston. What oil have you been using? How many miles on your engine?

    Good luck with your repairs. Let us know how the repairs work out. More engine photos would be interesting and welcome.

    Thank you.