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Thread: Front brake master cylinder & reservoir overhaul

  1. #1

    Front brake master cylinder & reservoir overhaul

    Hi everyone!

    Some of you might remember that I had some front brake issues/posts on the old Forum!
    Some of you asked me to let you know how I got on when I finally went back to the job, so here goes!...

    Here's a run down...

    Nov 2014: Bought my 1978 SR500
    The previous owner had fitted a non original front brake m/c, but kindly included the original one in the sale.
    I wanted to go back to the original one, but it looked very manky, so I needed to clean it & fit a piston kit.
    I needed/wanted to do a lot of other jobs, so the bike was off the road all that winter.

    June 2015:
    Couldn't deal with doing the m/c kit myself, so paid a local company to fit a good quality kit I bought, and also
    overhaul the front brake calliper and respray both items.

    I replaced the brake hoses myself, and fitted the newly overhauled m/c.
    On going to fit the calliper, I found that the company had assembled it incorrectly, and there was a shim in wrong,
    blocking the channel where the calliper fits over the disc!!

    I totally lost confidence in that company, and decided to do the job myself.

    I took the calliper apart, found one shim missing, one in back to front, one upside down, and one correct.
    Also the piston dust cover was not the correct one, & didn't fit properly/was too small. FFS!!! :-/
    I bought another calliper piston kit, and carefully did the job myself.

    Eventually mid June 2015 my bike was on the road with overhauled front brake calliper and original master cylinder, plus new brake pipes.
    Hooray!!

    All was fine for a couple of rides, and then I noticed that the master cylinder was leaking, despite the company telling me that they'd
    tested it for leaks. The leak has taken quite a bit of the paint off, which I'd also paid them to do. Not happy. :-(

    The company told me that they'd taken the reservoir off and ultrasonic'd all the parts, because the gunge had turned to crystals, which
    don't wash out. I was pleased they'd done such a thorough job. I asked them if they'd replaced the o ring underneath the reservoir and
    they said no, but that they'd treated it with some stuff that plumps rubber up. Hmmmm..?

    On looking closely after finding the leak, I noticed that the reservoir wasn't sitting down flush on the m/c body. No wonder there was a leak.

    I took the lid off, and tried to screw the reservoir down a bit more, but the company hadn't used the original screws (which I'd taken out, and which were in perfect condition) they'd used button headed allen socket screws. I managed to move one of them, but the other one just rounded out & wouldn't budge. I tried everything, but couldn't find a metric or imperial allen key that was a good enough fit to shift it, and I couldn't get a good purchase with molegrips, so I was stumped.

    In desperation to use the bike I bought a cheap master cylinder to use in the meantime, as the one that came on the bike was no good.

    I put the old, original m/c to one side, and every now and then tried something else to get the screw out, with no luck.

    Mid June 2015 - July 2017:
    Used the bike on and off, whilst doing a few little other jobs along the way, including changing the silencer and doing a full carb overhaul.

    Not sure I have the jetting/mixture correct, and worried that it might be running weak, so stopped using it for a while until I'm sure it's set up right.

    September 2017: Noticed that the front brake had stuck on whilst bike has been layed up.

    Decided to take calliper apart to clean and check it properly and whilst doing that, to finally try and sort the original
    master cylinder out!!

    Asked around various friends for advice, and a couple mentioned Torx bits as being very helpful for getting stubborn things out.
    I didn't even know what they were!
    Googled them!
    Bought some.

    TODAY... 10th October 2017.. (Almost three years after buying the bike!)...

    The Torx bits arrived.
    I gentlly knocked a slightly too big one into the rounded out allen bolt in the m/cylinder reservoir... and got the stubborn bolt out AT LAST!!!

    Having found so much wrong with the calliper that the company had worked on, and needing to sort the leak out, I definitely wanted to take the reservoir off, despite some people telling me to leave well alone!

    I'd read a good article about how to do it on these exact m/c's, and following that advice, I got it off easily!

    What I found underneath didn't really surprise me, having seen the shoddy work that the company had done on my calliper.

    Despite them supposedly having cleaned everything up untrasonically, there was gunge/crystals underneath the reservoir, and also what looks like black paint overspray!! (They sprayed my m/c remember :-/ ) I've cleaned all the gunge out carefully, using just brake fluid, and a tiny screwdriver/needle, to make sure the holes in the bottom aren't clogged. (hopefully)

    I then tackled the screw holes, using brake fluid and a long M5 bolt (after gently checking what thread it was, as I was slightly worried that the company might have jammed the wrong ones in, or threaded the stiff one). The threads felt very gritty, but after gently screwing a clean bolt in and out quite a few times & cleaning the dirty brake fluid that came out each time, they felt much better and I was happy.

    I then gently eased the o ring out.
    It's not smooth, and seems very non squishy and dead, if you know what I mean.
    I'm no expert, but I definitely feel like it should have been replaced.

    As many of you already know, you don't get one of the o rings in the piston kit unfortunately, so I've been reading up on them, making
    sure I get one that's ok with brake fluid!

    This evening I've ordered two new screws for the reservoir (cross head ones, like the original ones were), and a Nitrile o ring.
    I'm not 100% sure that the o ring I've ordered is thick enough though, so I might order a fatter one too, just to be on the safe side!

    If anyone has taken an SR500 Nissin 14mm reservoir off, and replaced the o ring, I'd be very interested and grateful to
    know what size they used!

    I felt SO elated when I eventually got that reservoir off today, having had it sitting on my bench with the rounded out screw stuck in it since June 2015!
    Yes, I could have taken it to someone, but I don't like being beaten, and am really chuffed that I eventually got the screw out & got it apart myself!

    Now let's hope I do a good job of replacing the o ring with the correct size, and getting it back together and not leaking! Hehe!

    Here are today's photos for those of you who asked for them!

    More cleaning to do on the m/cyl body, but I made a good start on it today, and the reservoir and other bits have cleaned up well. :-)

    More news to follow once the new o ring and screws arrive.
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    1978 SR500 Red/black. Original condition. In regular use
    1979 TS125 Red. Original (bit tatty) condition. In regular use
    2015 Ducati Scrambler 800 Red/black
    1972 CT2. Non UK registered long term project

  2. #2
    Senior Member
    Join Date
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    Location
    Sandpoint Idaho (almost)
    Posts
    132
    It looks as though you have gained experience (as in: "experience is what you get when you don't get what you want") Christine, and your experience with this part runs parallel to my own with many repair shops, unfortunately. But good that you have gotten to the "bottom" of the problem finally, and hopefully the new repair works well.

  3. #3
    Quote Originally Posted by gotsron View Post
    It looks as though you have gained experience (as in: "experience is what you get when you don't get what you want") Christine, and your experience with this part runs parallel to my own with many repair shops, unfortunately. But good that you have gotten to the "bottom" of the problem finally, and hopefully the new repair works well.
    Hehe, yes I've definitely learnt plenty of new things over these past few years!

    In the end, after reading up some more about how to judge what size o ring to use, I ordered two more sizes (thicknesses actually), so hopefully something will do the job.

    I'm a bit busy over the next few days, but I'll let you all know how I get on when I finally find the time to carry on with it! :-)
    1978 SR500 Red/black. Original condition. In regular use
    1979 TS125 Red. Original (bit tatty) condition. In regular use
    2015 Ducati Scrambler 800 Red/black
    1972 CT2. Non UK registered long term project

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