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1980 GS 400(Canada)/450(U.S.)E brake reservoir questions

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    1980 GS 400(Canada)/450(U.S.)E brake reservoir questions

    Greetings all,

    A couple of weeks ago I had the front brake reservoir replaced - the translucent plastic of the 37 year-old original had long since completely clouded over, and had even been flaking like plaster on some parts of the outside. Another consequence of the age was that two of the 4 reservoir cap screws broke off during removal, so the mechanics had to drill the old ones out of the base and create ‘taps’ (if I’m using the correct term) to screw them back into after the reservoir was replaced.

    There seemed to be a bit of leakage from under the cap on first install, but they thought it was stopped, and they said they didn’t want to put too much more torque on the replaced screw sockets for fear of stripping them.

    Now, having had the bike back for a few weeks, I know the reservoir is still leaking … slowly. I can put the handlebars at maximum tilt with the bike on its side stand for 5-6 hours and nothing appears, but after it’s been sitting much more upright on the center stand for a week, there IS fluid on the outside of the reservoir. I don’t have a definite “no” yet, but it’s looking like the aluminum base that the screws go into is among the parts no longer available for this old bike, so in case I can’t get a replacement, I have a couple of questions.

    - I’m thinking of trying to remove the cap and seeing if re-seating the diaphragm will help. If I do, are the cap screws supposed to be really tight, or just nicely snugged down? I ask because even though the mechanics were talking about tightening to the point of risking stripping the screws, it seems to me that tightening the cap down that much might pinch the rubber of the diaphragm to the point of opening up the seam.

    - Assuming the slow leak continues, do you know of any kind of squeeze/spray-on gasket or sealant I could put around the outside of the seam after the cap’s back on.

    - And when you apply the brake, is there ‘back pressure’ against the cap and the diaphragm - that might blow any sealant off anyway (or even eventually cause the new holes for the two screws to fail)?

    Being the original owner and having had 37 years of riding it, this bike could fall apart like a clown car tomorrow and I’d have no complaints, but it will be irritating if the thing that finally takes it off the road is a slow fluid leak (but obviously, this is a slow fluid leak that can’t be allowed).

    Thanks for any advice.

    #2
    Did you install a new diaphragm?

    looks like all the parts are still available new http://www.ronniesmailorder.com/oemp...aster-cylinder
    1978 Gs1085 compliments of Popy Yosh, Bandit 1200 wheels and front end, VM33 Smoothbores, Yosh exhaust, braced frame, ported polished head
    1983 Gs1100ESD, rebuild finished! Body paintwork happening winter 2017

    I would rather trust my bike to a technician that reads the service manual than some backyardigan that THINKS HE KNOWS how to fix things.

    Comment


      #3
      Why not just get a new master cylinder from EBay? There are plenty that will work just fine. http://www.ebay.com/sch/i.html?_odkw=gs400+master+cylinder&_osacat=0&_from =R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xsuzu ki+gs400+master+cylinder.TRS1&_nkw=suzuki+gs400+ma ster+cylinder&_sacat=0


      In fact, a new reservoir is still available too - http://www.ebay.com/itm/SUZUKI-GS400...JYlHNo&vxp=mtr
      sigpic
      Cowboy Up or Quit. - Run Free Lou and Rest in Peace

      1981 GS550T - My First
      1981 GS550L - My Eldest Daughter's
      2007 GSF1250SA Bandit - My touring bike

      Sit tall in the saddle Hold your head up high
      Keep your eyes fixed where the trail meets the sky and live like you ain't afraid to die
      and don't be scared, just enjoy your ride - Chris Ledoux, "The Ride"

      Comment


        #4
        I "replaced" one of these reservoirs just as you did and had the same problem. Turned out the new one was very different as to solidity at cap...metal in it....anyway, compare new parts to your old and see if they are obviously different. and put the old top back on...
        Go back to the shop and look through their garbage if they threw it out! (ALWAYS SAVE OLD PARTS!!!)

        If not, I would look for an entire replacement. old or new, (but I like the old if I can find it in decent condition..) The metal ones on ebay per cowboyups link with the inspection windows are similar to what I replaced my 81 gsx400T's Round plastic type with -I got mine off my 82 gsx400T parts bike so I can't directly say as to those pictured but they catch my eye as to "good" if seller guarantees fit for a very similar bike... You want a similar volume of fluid pushed to keep some feel in the brake so you want one intended for a single disc etc...
        Last edited by Gorminrider; 05-21-2017, 11:13 AM.

        Comment


          #5
          Thanks for all the input folks...

          Fjbj40, yes - the reservoir and everything above in in the schematic you have linked (diaphragm, diaphragm plate, cap, screws) were replaced as one - which was when 'new' screw holes had to be tapped into the "CYLINDER ASSY, MASTER MODEL T" at the bottom of that illustrated stack.

          Cowboyup, thanks for the suggestion - the possibility of an aftermarket replacement for such an obscure part from such an old model hadn't even crossed my mind. But then again, what CAN'T you get on eBay? Given the relatively low price but long delivery times from China, I might just order one now to get the wheels turning - so that if in a week or two and I haven't made any progress with the existing parts, the potential replacement might have arrived.

          Gorminrider - it appears that the replacement parts are OEM. They're still listed as available online and they certainly appear to be identical. (see attached image)...

          Old New.jpg

          Unfortunately, this replacement happened a couple of weeks ago, so there'll be no hope of retrieving the originals. (Oddly enough, I normally do - I've got the original camshafts sitting under my sink right now - as much as a souvenir as anything practical - but given the shape of the original and the nature of its contents, I didn't think in terms of keeping it.) And thanks for the 'single disk' pointer if I go the eBay route - it's another thing that wouldn't have crossed my mind, and I wouldn't have ever made the connection if the wrong choice had given me a different feel.

          One question, since you've done this before, and related to the mechanic's concern about the two tapped screw holes - when you replace the cap, do you tighten the screws as much as you might on a clamp or bracket, or just 'thumb and index finger tight' to make sure the cap is making a good seal with the diaphragm?

          Thanks again. The advice is appreciated.

          Comment


            #6
            Yes in your picture, they appear identical AND, if there's weight to your new cap (the metal plate included as shown as #5 in fjb40's post) then you're ok per my concern, but mine was oem too (40$!) and no plate was included. THEY might say, "of course not, The kit replaces plastics only" so I'm thinking possibly the shop that did all this also didn't notice... it took me awhile to figure out the problem! I noticed it was lighter eventually and I was awfully glad I had the old one around to get the plate out of. You can take the new diaphragm off lid and see but "weight "and solid feel of the cap will be the first clue....

            You don't need to tighten it down much.Just wrist--firm is all. Apparently,(I found) without the steel plate it's impossible and tightening it hard to seal is a bad idea as your shopguys said. I guess the plastic top alone just distorts the seal more and more...
            PLUG
            consider a set of JIS screw drivers. They dig straight into the screw so it's a better feel than always(unconsciously?) holding a bad fit down while turning it....I'm pretty happy with the set I got from Gofast http://www.thegsresources.com/_forum...rs-from-GoFast
            Z1 also has these.
            You will want to change brake fluid as a maintenance task, so the screws should never seize up in there again. a bit of NeverSieze might help long term but is yet another opinion...I would not be happy if it encouraged corrosion...(copper-types scare me graphite- type haven't seen an issue)

            Also (being insuch a mood for tips) Always cover your tank and seat with a cloth. Not just when fiddling around brake fluid but even mirrors or anything with a tool up there. a screwdriver or something is sooner or later going to get put on the tank or seat. It's impossible to resist! let alone accidents and scrapes.

            Comment


              #7
              Gorminrider,

              BINGO! Or at least it looks that way. I was planning to top up the fluid today to replace the seepage (the level had gone just a bit below the minimum line, and when it comes to my primary stopping power, ‘just a bit below’ is way too much), and when I read your post I went straight out to do it and have a look under the cap.

              No metal plate.

              So, I filled it up (to just below the maximum line), put the rubber diaphragm and cap back in place and tightened the screws to about an eighth of a turn less than they were (since I won’t be riding it again until I can put the plate in), and am about to go online and order the plate. (And a new diaphragm at the same time. If I don’t, and it keeps leaking, I’ll be wondering if it was because the current diaphragm was damaged during the ‘plateless’ period.)

              Re: JIS screwdrivers. Oddly enough I already had one in a size appropriate to the reservoir screws, in the form of a set of ‘jewelers’ screwdrivers’ I’ve had for years from working on Japanese-made cameras. (Nothing in the cameras needs a screw that big, but the set was extensive.) I’ll definitely get larger ones as the need arises.

              It will probably be a couple of weeks after installation before I'm confident of success, but when I am, I'll post that the problem has been solved.


              Thanks again - at least for the time being, I have reason to think I don’t have to replace the entire assembly.

              Comment


                #8
                Ok, I'm betting that was the problem. In my case the difference was immediate..a day or so made me sure any residual wiped up wetness was not new fluid.

                You wouldn't think it'd be so important to look at it but without that plate I recall would have fluid blown back onto the tank inside 20 miles.

                Comment


                  #9
                  Well, after waiting for parts, waiting for weather suitable for outdoor installation (open brake fluid reservoir and rain ... no thanks), and after a week or so of riding and parking with the handlebars at maximum tilt, I think it's safe to say, Gorminrider, you hit the nail right on the head.

                  And I was pretty confident as soon as it was installed. The plate tucks neatly into the diaphragm's pattern...

                  plates.jpg

                  ...and as I was tightening the reservoir cap over the new combo, I noticed something whose absence I had missed. A visible gap between the trim of the reservoir cap and a lip below on the reservoir itself. You can see it in the shot of the old crusty reservoir in an earlier post, and I've also included a before and after the plate installation, with the new reservoir.

                  So clearly the plate acts almost like a washer or a shim, pushing the diaphragm tight against an inside lip of the reservoir - and as you were saying, without that pressure, and since you'll never get a good seal of hard plastic against hard plastic, all the cap can do is sit on top and at best hold the leakage to a slow trickle.

                  So, at just over 37 years, still running - at least until the next age-related challenge. But in the meantime, thanks again for the guidance.
                  Last edited by Guest; 06-20-2017, 01:12 PM.

                  Comment


                    #10
                    Glad to hear my own tribulations helped someone! I have since noticed these "shim/stiffener" plates" in other Master cylinders. This 88 Honda I am fiddling with has a stiff plastic one so your "shim"idea hits the mark.

                    i suppose one could be made in a pinch.

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