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    Front master cylinder replacement

    Hi

    Im new to the forum having purchased a 1984 gs550e at the weekend. I have 3 other 70/80s Yamaha 2 strokes but suddenly had an 'itch to scratch' in terms of getting a GS as I had one back in the day! So now the work begins and the immediate problem is brakes

    Previous owner has fitted some sort of after market chinese m/c but it doesnt work very well, lever runs out of travel. No air in the system so can only assume the M/C is no good or wrong size

    I have twin disk so assume I need a 5/8 master cylinder, can someone make a recomendation of an aftermarket m/c that will connect to standard banjo fittings? I saw someone here uses EX650 m/c, do they connect to standard banjo fittings on a GS?

    Thanks in advance
    Last edited by ajh; 07-13-2021, 04:06 PM.

    1982 GS550Ez, 1980 Yam RD350LC 4L0, 1980 Yam DT175,
    1977 Yam RD250D(Sold)
    London UK

    #2
    Just be careful with your banjo bolts when mixing brands. Suzuki, at the time, used a 10mm x 1.00 thread pitch. Other Japanese manufacturers were and still are 10 x 1.25. Suzuki changed to 1.25 later, not sure exactly when. Just be sure you know what you got before you start threading bolts into MCs and calipers.
    Rich
    1982 GS 750TZ
    2015 Triumph Tiger 1200

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

    Comment


      #3
      My personal recommendation for the twin disc setup on most 80s GSs is the Honda Deauville (NTV700, iirc) m/c. Adjustable span, the right bore 5/8" and nice action. It's only a problem if you're more fussed about originality than function, and as you've found, the cheap ones are rubbish.
      As the Deauville m/c is made by Nissin, a decent Japanese maker of brake systems, I've got no qualms using them.
      ---- Dave
      79 GS850N - Might be a trike soon.
      80 GS850T Single HIF38 S.U. SH775, Tow bar, Pantera II. Gnarly workhorse & daily driver.
      79 XS650SE - Pragmatic Ratter - goes better than a manky old twin should.
      92 XJ900F - Fairly Stock, for now.

      Only a dog knows why a motorcyclist sticks his head out of a car window

      Comment


        #4
        If you want to stay with Suzuki - Bandit 600/1200 will work and the angle of the reservoir will also work nicely.
        Current:
        Z1300A5 Locomotive (swapped my Intruder for it), GS450 Cafe Project (might never finish it....), XT500 Commuter (I know - it's a Yamaha )

        Past:
        VL1500 Intruder (swapped for Z1300), ZX9R Streetfighter (lets face it - too fast....), 1984 GSX750EF, 1984 GSX1100EF (AKA GS1150)
        And a bunch of other crap Yamahas....

        Comment


          #5
          Thanks all, that gives me some options

          1982 GS550Ez, 1980 Yam RD350LC 4L0, 1980 Yam DT175,
          1977 Yam RD250D(Sold)
          London UK

          Comment


            #6
            If the caliper pistons are binding up it will result in the brake lever feeling soft. If you haven't already done so you might want to remove the caliper pistons, remove the seals, and then clean out any accumulation of grunge. Replace the brake lines too. Then if the hand lever feels mushy when the system is properly bled, pump up the lever best you can and tie the lever back against the bar for several hours. This will keep pressure in the system and allow the caliper pistons to move closer to the disc. You may have to do it a couple of times but if the pistons are moving freely the problem should go away. Of course, this assumes the master is okay. Master cylinders in of themselves are very simple devices and rarely fail unless there is corrosion in play.
            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

            Comment


              #7
              Originally posted by ajh View Post
              Thanks all, that gives me some options
              Thanks. My calipers are free and working and theres no air in the system. The brakes work fine to a point but theres too much travel in the lever to get full braking. Its a new unbranded M/C so Ive no idea what it is but Im guessing its the wrong size and needs more travel to achieve the force needed for hard braking. I tried some 'shims' between the piston and lever to reduce travel and I think this proved it was wrong because I could then get full braking but brakes were then binding a bit all the time

              1982 GS550Ez, 1980 Yam RD350LC 4L0, 1980 Yam DT175,
              1977 Yam RD250D(Sold)
              London UK

              Comment


                #8
                Originally posted by ajh View Post
                Thanks. My calipers are free and working and theres no air in the system. The brakes work fine to a point but theres too much travel in the lever to get full braking. Its a new unbranded M/C so Ive no idea what it is but Im guessing its the wrong size and needs more travel to achieve the force needed for hard braking. I tried some 'shims' between the piston and lever to reduce travel and I think this proved it was wrong because I could then get full braking but brakes were then binding a bit all the time
                Yeah, I went through this exact thing with my XS. After refurbing the OEM calipers I thought I'd try a 14mm master cylinder.
                Whooo....eeee - could stop on a dime/pebble/quarter/sixpence (choose your metaphor) but the lever came back too far for comfort.
                I ended up fitting the Deauville 5/8" m/c as it was still a size down from the Yamaha m/c (11/16" or 17.4mm) and gave excellent results.
                ---- Dave
                79 GS850N - Might be a trike soon.
                80 GS850T Single HIF38 S.U. SH775, Tow bar, Pantera II. Gnarly workhorse & daily driver.
                79 XS650SE - Pragmatic Ratter - goes better than a manky old twin should.
                92 XJ900F - Fairly Stock, for now.

                Only a dog knows why a motorcyclist sticks his head out of a car window

                Comment


                  #9
                  Originally posted by Grimly View Post
                  Yeah, I went through this exact thing with my XS. After refurbing the OEM calipers I thought I'd try a 14mm master cylinder.
                  Whooo....eeee - could stop on a dime/pebble/quarter/sixpence (choose your metaphor) but the lever came back too far for comfort.
                  I ended up fitting the Deauville 5/8" m/c as it was still a size down from the Yamaha m/c (11/16" or 17.4mm) and gave excellent results.
                  thanks for that!

                  1982 GS550Ez, 1980 Yam RD350LC 4L0, 1980 Yam DT175,
                  1977 Yam RD250D(Sold)
                  London UK

                  Comment


                    #10
                    Most used master cyl's have had poor service and the bores get wore outand are not worth rebuilding. Get a fairly modern, less than 5 year old m/c with low miles or get a new one from Z1. Smaller bore sizes (1/2")tend to have a better feel. Went through this with my ZRX. Naked bikes have fairly flat bars so they tend to fit/look a little more normal. Calipers have to be perfectly clean, no corrosion in seal area, seals greased properly and new OEM seals only. GS's with modern, well working brakes are an amazing improvement.
                    Current Rides: 82 GS1100E, 00 Triumph 955 Speed Triple, 03 Kawasaki ZRX1200, 01 Honda GL1800, '15 Kawasaki 1000 Versys
                    Past Rides: 72 Honda SL-125, Kawasaki KE-175, 77 GS750 with total yosh stage 1 kit, 79 GS1000s, 80 GS1000S, 82 GS750e,82 GS1000S, 84 VF500f, 86 FZR600, 95 Triumph Sprint 900,96 Triumph Sprint, 97 Triumph Sprint, 01 Kawasaki ZRX1200, 07 Triumph Tiger 1050, 01 Yam YFZ250F
                    Work in progress: 78 GS1000, unknown year GS1100ES

                    Comment


                      #11
                      I've used EX650 ones for years. Work great...
                      1980 GS1000G - Sold
                      1978 GS1000E - Finished!
                      1980 GS550E - Fixed & given to a friend
                      1983 GS750ES Special - Sold
                      2009 KLR 650 - Sold - gone to TX!
                      1982 GS1100G - Rebuilt and finished. - Sold
                      2009 TE610 - Dual Sporting around dreaming of Dakar.....

                      www.parasiticsanalytics.com

                      TWINPOT BRAKE UPGRADE LINKY: http://www.thegsresources.com/_forum...e-on-78-Skunk/

                      Comment


                        #12
                        If you’re still looking for options. I put my 2004 SV650N MC on my ‘79 850. The N model incorporates the mirror attachment if that makes sense. Not sure if your bike uses the remote reservoir or not. If it does then the Sv S model would work.
                        1979 GS850G
                        2004 SV650N track bike
                        2005 TT-R125 pit bike
                        LRRS #246 / Northeast Cycles / Woodcraft / Armour Bodies / Hindle Exhaust / Central Mass Powersport

                        http://s327.photobucket.com/albums/k443/tas850g/

                        Comment


                          #13
                          So got myself a used Bandit M/C with adjustable lever and it works great. Thanks for the help all!

                          Quick question, I found the bleed nipples on my calipers have been butchered, can anyone tell me the threadsize of the bleed nipples to buy new? (Save me having to take one out and have to rebleed brakes )

                          thanks
                          Last edited by ajh; 07-20-2021, 05:14 PM.

                          1982 GS550Ez, 1980 Yam RD350LC 4L0, 1980 Yam DT175,
                          1977 Yam RD250D(Sold)
                          London UK

                          Comment

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