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Thread: Master cylinder help!?!

  1. #1
    spaken71
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    Master cylinder help!?!

    My master cylinder is leaking around the piston. does anyone know a good place to get a rebuild kit aftermarket without going to BMW?

  2. #2
    brentde3
    Guest
    Not that I'm aware of. There are a bunch of places that have different prices (tried Hucky's or eubmw.com?). If you're looking to replace the whole thing there's always eBay or whatnot.

    I found that mine was leaking because of years of neglect (and water in the brake fluid). It had rusted and pitted out the cylinder. I was told that I could probably rebuild it and make it last "a while," but I didn't like the sound of that. Apparently no one makes an oversize kit so that one could just hone the cylinder. I wound up going to Motobins (out of the UK) and buying a kit to install a handlebar mounted master cylinder. Best thing I've done so far to the bike.

  3. #3
    Liaison 20774's Avatar
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    Ted Porter at the Beemershop is also a good source. He should know exactly what you need.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  4. #4

    Kit for a handlebar mounted MC

    Quote Originally Posted by brentde3 View Post
    Not that I'm aware of. There are a bunch of places that have different prices (tried Hucky's or eubmw.com?). If you're looking to replace the whole thing there's always eBay or whatnot.

    I found that mine was leaking because of years of neglect (and water in the brake fluid). It had rusted and pitted out the cylinder. I was told that I could probably rebuild it and make it last "a while," but I didn't like the sound of that. Apparently no one makes an oversize kit so that one could just hone the cylinder. I wound up going to Motobins (out of the UK) and buying a kit to install a handlebar mounted master cylinder. Best thing I've done so far to the bike.

    I have the old ATE under the tank mounted MC. Would like more info on the kit you bought. Did it have brake lines as needed??
    1974 R75/6 W Sidecar
    1989 R100GS


  5. #5
    rocketman
    Guest
    Quote Originally Posted by 85K100LT View Post
    I have the old ATE under the tank mounted MC. Would like more info on the kit you bought. Did it have brake lines as needed??
    Yeah, so would I. I'd love to get rid of the cable section of the brake. Teh steel line helped reduce the "spongyness" but the cable section is a pita and reduces the feedback a disk system should have.

    RM

  6. #6
    Quote Originally Posted by spaken71 View Post
    My master cylinder is leaking around the piston. does anyone know a good place to get a rebuild kit aftermarket without going to BMW?
    I just rebuilt mine with a kit supplied by Capital Cycle - it was the best price I found.

    In my research on rebuilding the "double wrap of floss" technique around one of the seals was very helpful in getting it in place on the piston - as well as using some common silicone valve grease - which is kind to O rings.

    I also "honed" and polished the walls of the bore with some 12000 grit micro-mesh cloth.

    I spray glued a small rectangular section of the cloth on to a 4" long piece of 5/8" wood dowel, then made a mandrel that could be chucked in my cordless drill using a small section of threaded rod, which screwed into the center of the dowel via a drilled hole. I used the drill on slow speed and moved the dowel in and out polishing the length of the bore until it looked like a mirror.

    If you've got any pits on the walls of the bore - except at the very front where the seal doesn't wipe - you are probably into buying the whole $$$$ shebang.

  7. #7
    brentde3
    Guest
    Here's a link:

    http://www.motobins.co.uk/displayfin...cylinder&go=GO

    It's part number 61170 a little bit down the page. It's a nice kit, in general. The mirror isn't exactly right (slightly different shape than the stock mirror), but the good stuff is all very good. It's brand new, made by Magura, so it was all very plug and play.

    Because it's a kit that's trying to cover a lot of bikes, it comes with a splitter. That was the one part that I wasn't exactly excited about. One hydraulic line from the master cylinder to the splitter under the tank, one line down to the caliper. The kit only comes with one bit of stainless line to go from the cylinder to the splitter. They expect you to use whatever line you all ready had to go to the caliper.

    They do this, I think, to cover the dual disc bikes. I don't have dual discs, and I'm not planning on going that route any time soon, so I had the Beemershop (another plug for those guys...they do great work) build me a custom stainless line to go directly from the master cylinder to the caliper. Now there's nothing under the tank! Even with that little caveat, and the money I spent building a custom line (which I'm sure you don't have to do), I was still way under the cost of a new under-tank master cylinder.

    Hope that helps.

  8. #8
    spaken71
    Guest
    Thanks guys for all of the help. I'm pretty sure I just need the seals on the piston but I may look into a handlebar mount if its not too pricey. I hate haveing to pull the tank.

  9. #9
    Just for grins I did some shoppin' and convertin'.: This is just a quick "snap shot" look:

    Motobins single disc converter kit, $359.00

    Motobins ATE single disc reservoir, $281.00

    Capital Cycle ATE single disc reservoir, $373.00

    I ship to the UK and Europe fairly frequently - and by priority mail it's actually pretty reasonable both ways. Even Express mail (which from us to them includes a tracking number) is still not that expensive.

    Since I've been buying a lot of small components lately I have REALLY found that it pays to shop around. Current prices on our parts are all over the place...

  10. #10
    spaken71
    Guest
    thanks for checking. BMW wants over $400 for the whole thing.

  11. #11
    There is nothing magical about hydraulic brake lines. With the appropriate master cylinder on the right perch, you can either go to the splitter (BMW mounts the electronic ignition module under tank, using the splitter as a heat sink!) with one line, then on to the two brake cylinders, OR you can go from the m/c to one brake cylinder and jump over to the second, OR you can get a dual-fitting right at the m/c and run two lines down to the brake cylinders. The beauty of hydraulics is that they don't care much how you route them, how even the lines are, etc.

    There are many people who make custom stainless-braid brake lines, not terribly expensive (read: cheaper than BMW original!) that can be ordered online. Take a piece of inexpensive plastic tubing and run it on the route(s) that you want, measure it, and order. Ends can be had in straight, ell, 45, 15 degrees, etc, and in many colors if you want!

    BTW it is better to order it an inch TOO LONG than an inch too short...damhik....

  12. #12
    spaken71
    Guest
    Thanks again for all of the great support guys. After hearing the suggestions and checking with the mark-up artists at the Beemer dealer, I think I will consider the handlebar mount braided line route.

  13. #13
    Grammarian no, Rider yes ISAMEMON's Avatar
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    speigler did my cusom lines when I converted my 78 ( which I no longer own) and did my lines for my current bmw ride an 85

  14. #14
    mymindsok
    Guest
    +1 on the Speigler lines.

    They give great service!

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