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Thread: Spring on rear brake pedal - K75S

  1. #1
    Tom Mieczkowski mieczkow's Avatar
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    Mar 2006
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    St Petersburg, FL
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    292

    Spring on rear brake pedal - K75S

    I've been doing a rebuild on my rear master cylinder and everything has come out well. However, as I completed the work, and was staring at the drawings in the Haynes manual I noticed something that has led me ask for some guidance.

    According to the drawing there is a sort of external return spring or helper spring shown which runs from a little L-shaped bracket on the aft part of the pedal (where the adjuster stud is) going forward to a bolt. From the drawing it would exert force forward, sort of pulling the pedal away from the piston. It seems this would help support the pedal in the "return" or non-braking position.

    Well, that spring has never been on the bike for the three years I have owned it. So I am a little baffled as to whether the K75S had this spring or this is a spring only associated with K75's with a drum rear brake, or some other deal I am not imagining.

    It seems the pedal returns just fine relying on the return spring which is integral to the piston. So, do I need this spring or not? Is it unhealthy to rely on the spring tension provided by the master cylinder piston alone to support the pedal?

    Opinions? Commentary? Many thanks!!
    Tom Mieczkowski
    1987 K75S

  2. #2
    Registered User
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    Mar 2008
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    Belton Tx
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    I just looked at my 91 75RT ABS. It has a spring running from the L bracket to the same post the center stand springs anchor on.
    I think an external spring in this area is needed to insure that it maintains freeplay between the pedal linkage and the piston.

    I have read of people adjusting the brake pedal height and not maintaing the freeplay. This resulted in locked brakes and one brake fire.

  3. #3
    Tom Mieczkowski mieczkow's Avatar
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    Mar 2006
    Location
    St Petersburg, FL
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    292

    Spring

    Ron,

    Thanks for the response - I located the slot on the post where the spring would connect. I fabricated a temporary solution by using an existing spring. Next time I'm ordering some stuff from Max BMW I'll add that sprong to the order. It does look like it is really just a "helper" to avoid load on the return spring in the piston.
    Tom Mieczkowski
    1987 K75S

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