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    Caliper cleaning/old brake fluid

    I’ve torn my calipers down, and the pistons are in great shape, but the actual part of the caliper that holds the piston has brown stains from the old brake fluid that was sitting for god knows how many years.

    ive cleaned the calipers with brake kleen (enough to where the paint is mostly off), but I can’t get the brown film off. Any suggestions on what to use to get this off or what else I can try?

    if I don’t get the brown off should my calipers still be ok since the pistons are in good shape?
    Main lady- 2009 Nightster 1200
    Project Lady- 1982 GS650 G

    #2
    Carb dip?

    Important thing is to remove any corrosion or crud in the seal groove and off the pistons. Then install new seals and your calipers should be okay. Use heavy black moly caliper grease for the sliding pins. Replace the lines too.
    Ed

    To measure is to know.

    Mikuni O-ring Kits For Sale...https://www.thegsresources.com/_foru...ts#post1703182

    Top Newbie Mistakes thread...http://www.thegsresources.com/_forum...d.php?t=171846

    Carb rebuild tutorial...https://gsarchive.bwringer.com/mtsac...d_Tutorial.pdf

    KZ750E Rebuild Thread...http://www.thegsresources.com/_forum...0-Resurrection

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      #3
      Wire brush or blasting
      Repaint
      Be sure all residue is off before Assembly
      1978 GS 1000 (since new)
      1979 GS 1000 (The Fridge, superbike replica project)
      1978 GS 1000 (parts)
      1981 GS 850 (anyone want a project?)
      1981 GPZ 550 (backroad screamer)
      1970 450 Mk IIID (THUMP!)
      2007 DRz 400S
      1999 ATK 490ES
      1994 DR 350SES

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        #4
        With new seals make sure the piston and the seal are well lubed up with brake fluid. Too much friction between the seal and piston will stop the piston slipping through the seal to self adjust for pad wear. It will cause excessive lever travel, you'll think it's air in the line, but bleeding will not fix it
        sigpicDarryl from Kiwiland

        1982 GSX1100S Katana
        1982 GSX750S Katana
        1982 GS650G Katana

        Comment


          #5
          Originally posted by Big T View Post
          Wire brush or blasting
          Yes, but NOT inside the bores!

          Just to be clear...
          1983 GS850G, Cosmos Blue.
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            #6
            Thanks for that clarification. The brown spots are inside the bore.... i tried to use sandpaper by hand a bit and it worked... did i totally just mess up my calipers? Having a blond moment here.
            Main lady- 2009 Nightster 1200
            Project Lady- 1982 GS650 G

            Comment


              #7
              The piston surface that contacts the rubber seal is the only one to care about....Immoveable (iron-oxide?)stains in the bottom of the bore are unlikely to hurt anything. It's probably molecular from the old hose fittings....

              Comment


                #8
                I'd have reached for a green scotch brite pad. That and WD40 (right or wrong) have been my go-to for cleaning gunge off/out of aluminum parts: gasket surfaces, brake pot recesses, and lots of other stuff. You have to press super hard to removes anything but the offending crud. If I need to get more aggressive or feeling lazy I go for these on my dremel. Worked a treat on cleaning up the inside of my front wheel that had a lot of corrosion. They wear quickly and a bit pricey, but sometimes I just don't feel like spending hours rubbing with a pad by hand.
                Rich
                1982 GS 750TZ
                2015 Triumph Tiger 1200

                BikeCliff's / Charging System Sorted / Posting Pics
                Destroy-Rebuild 750T/ Destroy-Rebuild part deux

                Comment


                  #9
                  yes ^^ handy, but not "harmless"- scotchbrite can do a lot of harm in the wrong place...Whenever polishing. I remind myself water can wear a stone

                  Comment


                    #10
                    Originally posted by Gorminrider View Post
                    yes ^^ handy, but not "harmless"- scotchbrite can do a lot of harm in the wrong place...Whenever polishing. I remind myself water can wear a stone
                    Yes, I understand that the scotchbrite is abrasive and if you're not careful, can remove aluminum, But with all the gasket surfaces I've cleaned with it, I found if I keep it wet w/ WD40 and let the pad do the work, w/ only a little pressure, I think I do OK. YMMV.
                    Rich
                    1982 GS 750TZ
                    2015 Triumph Tiger 1200

                    BikeCliff's / Charging System Sorted / Posting Pics
                    Destroy-Rebuild 750T/ Destroy-Rebuild part deux

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                      #11
                      ^^ +1 : using the soft scotchbrite and WD40 i have
                      never seen scratches created in the bores.

                      Those are handy too : after most crud is gone i
                      wrap them thick in cloth and put some Belgom Alu on it.
                      The bores on my calipers shine like chrome

                      Did i mention i like shiny things ?
                      I also polish the brass parts in/on my carbs like plugs,
                      jets, choke, fuel pipe, etc.
                      Last edited by Rijko; 09-24-2021, 12:26 PM.
                      Rijk

                      Top 10 Newbie Mistakes thread

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                        #12
                        Originally posted by Rijko View Post
                        ^^ +1 : using the soft scotchbrite and WD40 i have
                        never seen scratches created in the bores.
                        oh wait i have ... the central part of the Dremel tool could damage
                        the bottom of the caliper bore, so i always use it at an angle so
                        that won't happen.

                        Though scratches on the bottom don't hinder functionality
                        i dislike them as the purpose is a mirrorlike finish, and
                        improve not damage the calipers.
                        Rijk

                        Top 10 Newbie Mistakes thread

                        CV Carb rebuild tutorial
                        VM Carb rebuild tutorial
                        Bikecliff's website
                        The Stator Papers

                        "The thing about freedom - it's never free"

                        Comment


                          #13
                          The condition of the bore isn't important, just the seal groove. Use a gray scotchbrite pad or brass wire wheel on a dremel, running at low speed, and remove all corrosion in the seal groove. Then install new OEM seals, and make sure the pistons are not pitted. Do this and you will be good.
                          Ed

                          To measure is to know.

                          Mikuni O-ring Kits For Sale...https://www.thegsresources.com/_foru...ts#post1703182

                          Top Newbie Mistakes thread...http://www.thegsresources.com/_forum...d.php?t=171846

                          Carb rebuild tutorial...https://gsarchive.bwringer.com/mtsac...d_Tutorial.pdf

                          KZ750E Rebuild Thread...http://www.thegsresources.com/_forum...0-Resurrection

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