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R1150RT front brake master cylinder repair kit?


Cap

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Hi,

 

My front brake felt soft on my 2004 R1150Rt with EVO brakes. I hadn't flushed the system for 2 years, so I set about doing that. But I also wanted to install my new Spiegler SS brake lines at the same time. That's the back story -- everything went fine with that.

 

But after installing the lines and flushing the wheel circuits, when I was flushing the front control circuit, I noticed that I was not getting a full pump from the front lever. I anticipated some squishy-ness because I had replaced the line from the lever. But this is really different, sometimes a squeeze produces nothing. So, my guess is that my front brake master cylinder needs an overhaul.

 

 

My question is, "does anyone have experience with this?" What is your recommended kit? What part number did you use? I see that Magura sells a kit for the 1150, using a 16mm piston. Is that the right one for EVO brakes? As an aside Beemer Boneyard claims that Magura is being sued by BMW, and thus BB won't sell Magura kits anymore. So, if you have another supplier, that would help.

 

 

TiA, Cap

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I had the same thing after replacing my front brake hoses. I believe that if you slowly pump the front brake lever you will see a small bubble each time you pump it. Do this without the wheel cylinder bleed valve open. That indicates you still have air in the line at the master cylinder. Just keep it up for a long time until you no longer see the air bubble in the master cylinder reservoir each time you slowly pump it.

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I had the same thing after replacing my front brake hoses. I believe that if you slowly pump the front brake lever you will see a small bubble each time you pump it. Do this without the wheel cylinder bleed valve open. That indicates you still have air in the line at the master cylinder. Just keep it up for a long time until you no longer see the air bubble in the master cylinder reservoir each time you slowly pump it.

 

Thanks, I noticed that too. And I did pump it until the bubbles stopped. But this is different: I can pull the handle all the way in, and see no movement in the waste line from the control circuit bleed nipple.

 

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Hi,

 

My front brake felt soft on my 2004 R1150Rt with EVO brakes. I hadn't flushed the system for 2 years, so I set about doing that. But I also wanted to install my new Spiegler SS brake lines at the same time. That's the back story -- everything went fine with that.

 

But after installing the lines and flushing the wheel circuits, when I was flushing the front control circuit, I noticed that I was not getting a full pump from the front lever. I anticipated some squishy-ness because I had replaced the line from the lever. But this is really different, sometimes a squeeze produces nothing. So, my guess is that my front brake master cylinder needs an overhaul.

 

 

My question is, "does anyone have experience with this?" What is your recommended kit? What part number did you use? I see that Magura sells a kit for the 1150, using a 16mm piston. Is that the right one for EVO brakes? As an aside Beemer Boneyard claims that Magura is being sued by BMW, and thus BB won't sell Magura kits anymore. So, if you have another supplier, that would help.

 

 

TiA, Cap

 

Evening Cap

 

I don't have a lot of time for a full reply so this will have to be brief.

 

You might just have an air-in-the-upper system problem but you seem to think that it more involved than that.

 

So, assuming it ISN'T an air bound issue in the upper brake system then possibly 3 problems--

 

First, is the master cylinder piston seal is bad due to you stroking the piston past it's normal travel so the piston seal traveled into a curded up area of the cylinder bore ( piston is 16mm on the I-ABS EVO system)

 

Next, is that the piston isn't quite returning all the way back to it's out stop ring (if piston doesn't FULLY return to it's out-stop then new fluid can't get into the piston bore (so check this).

 

Next, is that the very small take-up-port hole in the bottom of the master cylinder reservoir is plugged (or partially plugged) so new fluid can't get into the piston bore (also check for this)

 

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First, is the master cylinder piston seal is bad due to you stroking the piston past it's normal travel so the piston seal traveled into a curded up area of the cylinder bore ( piston is 16mm on the I-ABS EVO system)

 

 

Thanks for confirming 16mm bore. I didn't stroke past the normal travel... at least until it had already exhibited the non-pumping action. The other stuff is already checked and eliminated as potential reasons. As an aside, I did find that the BMW OEM parts are still available to rebuild the cylinder, so I can do that if I want.

 

D-R, can you tell me if I need special tools to repair the seal? It looks like maybe I need a lock-ring plier to get the piston out -- nothing exotic in the tool department.

 

Cap

 

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D-R, can you tell me if I need special tools to repair the seal? It looks like maybe I need a lock-ring plier to get the piston out -- nothing exotic in the tool department.

 

Cap

 

Morning Cap

 

You will either need a small tip snap-ring pliers or you can work the snap ring out using an awl or pick with a tip that will fit into one of the snap ring holes.

 

32722333062_1_B.jpg

 

 

 

 

 

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