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Thread: 1988 K75 Low Seat: Front Master Cylinder or Just Piston

  1. #1
    Still plays with trains. tinytrains's Avatar
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    1988 K75 Low Seat: Front Master Cylinder or Just Piston

    My front master cylinder has been leaking for a while. I pulled out the piston today and took a look inside. there are some small pits on the bottom of the cylinder. I have smoothed them off with 600 grit paper.

    So the question is: do I need a whole new front brake master cylinder? Or just a new piston.

    Thanks,
    Scott

    1988 K75 Low Seat
    2009 R1200R Roadster

  2. #2
    A bozo on the bus deilenberger's Avatar
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    I'd be looking for a new cylinder. Those pits look too deep to sand or hone out, and eventually they will destroy the seal on the new piston.
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders New Sweden BMW Riders
    '07 R1200R (current ride) and some bimmers.. and a Porsche

  3. #3
    Still plays with trains. tinytrains's Avatar
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    Thanks Don. That was my suspicion, and no point spending $70 on a piston and then another $200 on a MC with a piston.

    The damn thing is only 23 years old!
    1988 K75 Low Seat
    2009 R1200R Roadster

  4. #4
    Still plays with trains. tinytrains's Avatar
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    New MC installed. Despite much flushing of the fluid, I had trouble getting the air out of it. So I took a syringe (no needle) stuck it over the hole in the bottom of the reservoir and pulled up the plunger. This sucked the air right out! A few strokes of that, an the lever is nice an firm.
    1988 K75 Low Seat
    2009 R1200R Roadster

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