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Is R1200RT (06) Rear master cylinder repairable.


WestyLancs

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Hi all. More curious than anything else.

 

I have a late 2006 R1200RT (Gen 2 ABS, 68K miles) and whilst checking for the source of a minor oil seepage, I came across signs of a brake fluid leak from the rear master cyclinder. I assume it's just started, as there is no indication on the garage floor, and there was very little fluid inside the rubber boot on the cylinder, and the reservoir was still at MAX.

 

I have no problem sourcing a used replacement, or even a new part (at double the cost), but wondered if anyone was aware of a repair kit for it?

 

I have scoured the internet using my best attempt at search phrases, but can only find repair kits for earlier bikes.

 

The brake cylinder is the Brembo stamped model, from the gen 2 ABS version.

 

No doubt, if a kit is available, the cost, and time of shipping, may make a straight swap the easier option, especially with the riding season fast approaching, but curious minds need to know...

 

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The parts fiche does not show any replaceable parts that would stop the behind-the-boot seepage you describe.

 

Considering the very few drops that collected over ten years, I'd just clean the area thoroughly and make inspection part of my regular maintenance routine. It's not likely to fail suddenly, just watch for increased leakage in the form of visible drips.

 

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Afternoon Lan

 

Nothing from BMW but you do have some options.

 

If it were mine I would remove the cylinder & take it apart then clean the bore & piston up.

 

If all OK looking then I would re-assemble & see if it leaks. Possibly just some crud is caught under a seal.

 

You might be able to source basic piston seals from your local auto parts store from an automotive kit (if you have a sharp parts man at your local auto parts store)

 

You might also call Beemer Boneyard-- they don't show anything on the Gen-II rear master cyls but they might know of a source.

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Thanks for the replies. It's coming off in the next couple of days, no matter what, so there's nothing lost by taking the piston out and giving it a good clean. If that sorts it, great, if not, I'm no further back than I am now.

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  • 3 weeks later...

Quick update for info.

 

Finally got round to fitting a new unit this weekend, without problem, and decided to see if I could strip the old unit to check for wear.

 

I've looked at the old unit, and can find absolutely no apparent way of removing the piston from the cylinder to check / clean the seals, without causing damage..

I can feel a physical 'stop' of some kind, preventing the piston from being withdrawn, but there is no evidence of any kind of retaining clip, or pin. The bottom of the piston has a groove across its diameter, but refuses to budge with any kind of screwdriver I possess, so doesn't appear to be a screw, or twist lock fit.

 

My assumption (and that is all it is) is that there is some form of one way catch on the piston, that engages on initial assembly with no facility to disengage it for service.

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Don_Eilenberger
Quick update for info.

 

Finally got round to fitting a new unit this weekend, without problem, and decided to see if I could strip the old unit to check for wear.

 

I've looked at the old unit, and can find absolutely no apparent way of removing the piston from the cylinder to check / clean the seals, without causing damage..

I can feel a physical 'stop' of some kind, preventing the piston from being withdrawn, but there is no evidence of any kind of retaining clip, or pin. The bottom of the piston has a groove across its diameter, but refuses to budge with any kind of screwdriver I possess, so doesn't appear to be a screw, or twist lock fit.

 

My assumption (and that is all it is) is that there is some form of one way catch on the piston, that engages on initial assembly with no facility to disengage it for service.

Ian, have you tried air-pressure? Pushing it out usually works. On earlier BMW master cylinders there was a screw in the side of the cylinder that had to be removed in order for the piston to come out. I'm guessing that's not the case here since it would be rather obvious.
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Hi Don. I've tried pushing it out from the top of the cylinder with a metal rod. Definitely feels like there's some physical stop, as opposed to friction, or seal resistance. As you say, no sign of any screws, fittings, or access holes for internal release catches.

As I posted, I have a new one fitted so all's well with the bike. I was just curious, and may even take a hacksaw to it in due course to satisfy my curiosity.

Thanks again.

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