Clutch and Brake Master Cylinder Rebuild

[Dave_Faria]

GM List. To start I own a R1150RT with 72k miles and I change all brake fluid in both clutch and brake systems every 12k miles so I don't think I will ever have any problems with the systems(I hope). But, what I wantd to ask is can the master cylinders be successfully rebuilt if they ever leak. Rebuild kits are now available and I was thinking about picking up a kit for each system because of the price increases of things from overseas. I rebuilt the brake master cylinder for my 1978 R80/7 without any problems. So:

1. Are any special tools needed for the rebuild???
2. Will they probably still leak after rebuild???
3. Any wisdom you want to share???

Thanks Again List

[GSAddict]

GM List. To start I own a R1150RT with 72k miles and I change all brake fluid in both clutch and brake systems every 12k miles so I don't think I will ever have any problems with the systems(I hope). But, what I wantd to ask is can the master cylinders be successfully rebuilt if they ever leak. Rebuild kits are now available and I was thinking about picking up a kit for each system because of the price increases of things from overseas. I rebuilt the brake master cylinder for my 1978 R80/7 without any problems. So:

1. Are any special tools needed for the rebuild???
2. Will they probably still leak after rebuild???
3. Any wisdom you want to share???

Thanks Again List

Be sure to lubricate the little bearing (with high temp wheel bearing grease)at the end of the clutch slave. That is what typically fails due to there being very minimal grease there right from the date of mfg. I have proof in pictures of new slaves I have installed for others. I have lubed my own twice and still on original slave @ 190,000 km. Changing the fluid every season is also a must from a PM point of view.
The other thing to do is to cut away the protective foam cover at the bottom of the pressure line (where it connects to the slave) coming from the master cylinder. Cut back so fitting metal is fully exposed. Water typically collects there from the upper end and eventually rusts the fitting out where it is crimped.

[henzilla]

I have rebuilt a leaking front brake master on an 1100R. As long as it is not leaking,really not an issue. If it is, and it is just the seals, no problem replacing them. Takes longer to get the controls off than it does the rebuild. The problem comes if the cylinder bore is pitted and you cannot smooth it out. Then it becomes a replacement issue. Ours started leaking at high altitude and spewed fluid inside the handguards.Once below 1000' it stopped...for awhile. Was not overfilled, the seals just started breaking down and I found minor pitting in the bore that I could smooth out. I had done a fluid flush a few months before, but the PO had done little the first few years and the fluid was really nasty by the time I did.
Sounds like you have done enough fluid changes to prevent the main pitting causes, which is moisture and crud in the fluid.I do understand the price issues and buying one now for future use. When I did the 1100, BMW did not list a kit...but the 850R did have one...same bike. I saw BeemerBoneyard now has them.
I did use a Mity-Vac to purge the system afterwards to get all the air out .Conventional squeeze and loosen method wasn't getting it done.No other special tools were needed...just patience.

[PETDOC]

I have lubed my own twice and still on original slave @ 190,000 km. Changing the fluid every season is also a must from a PM point of view.
The other thing to do is to cut away the protective foam cover at the bottom of the pressure line (where it connects to the slave) coming from the master cylinder. Cut back so fitting metal is fully exposed. Water typically collects there from the upper end and eventually rusts the fitting out where it is crimped.

Having had my slave cylinder's throw out bearing go after 31,000 miles I'm curious about how you serviced yours. Did you clean the recess where the bearing sits prior to adding more grease? If so, what did you clean it with?

[Dave_Faria]

Thanks henzilla. It gives me a little more confidence. I own an 2004 RT with 72k miles and so far all is working fine. If I have to rebuild the master cylinders(clutch, brake) I will run a few days without the fairing or maybe a week or two to make sure they don't leak.

I saw the rebuild kits on the beemer boneyard site and am probably going to get one and rat hole it. I appreciate the mightyvac idea.

Thanks agn

[Dave_Faria]

Thanks GSaddict for your comments too.