Rebuild or replace master cylinder?

[drpetecrocker]

Two years ago I moved my 1974 /6 from Phoenix where it was dry and warm to Iowa where it is cold and wet. All winder it sat in a damp garage, and this spring, upon starting it up, I noticed that the front brake lever would squeeze all the way to the grip. I then noticed that there was a pool of fluid on the ground. It's brake fluid, and it also ate the paint off the top tube of the frame. There is no leak from the hose connection. There was a lot of fluid inside the rubber boot, so I assume it's the piston at-least. My question is whether it is worth rebuilding the cylinder or is it better to just replace it? Thanks.

 

[chunk]

I went with the rebuild kit. It was quite easy to do and hasn't leaked drop. At least 3 years ago, maybe more. Silly place for a master cylinder though, reminds me of a VW, inside the cabin and when it leaked it was on your trousers.

 

[20774]

Welcome to the forum!

I'd probably pull the M/C off and open it up so that you can check the bore for any serious corrosion. If it's that far gone and you can't lightly hone the bore, then either a new one or possibly sending it off to have it sleeved. There are sources for that worked listed in the resource link in my signature block.

 

[dennisdarrow]

Not to argue about the placement of the M/C, it is what it is and where it is. For me, when the time came, due, just as possibly yours to ignoring the proper maintenance, I first chose rebuild it myself. Easy to hone the cylinder using a dowel and piece of sandpaper of various grades. MANY videos on this are available on Youtube.................Then came the new seals. For this old clumsy fingers was almost next to impossible without tearing one. Yes, used dental floss and other "tricks". Got it back together and wah freaking lah within 1K miles it was dripping again. This time between the reservoir and the body of the M/C..........So.......

Sent it off and for maybe $100 or so got it back in a few days. Many thousands of miles and hours later and the thing is still like new. Used the opportunity to change out my original hosing to SS.......Supposedly really makes a diff but for me it is just a set of seventy's brakes working...........good luck......God bless.......Dennis

 

[SCBuckeye]

I rebuilt mine with zero problems and no leaks yet after 1 yr. and several months! My hardest problem was getting that seal ring over the plunger!

I did use the dowel and wet or dry sandpaper to get it mirror smooth!

 

[yankeeone]

I just did mine 78 r80/7 and I used the cap from a sharpie pen to guide the plunger on the shaft, worked perfect. find one that fits over the shoulder of the shaft.

 

[SCBuckeye]

Sent it off and for maybe $100 or so got it back in a few days. Many thousands of miles and hours later and the thing is still like new. Used the opportunity to change out my original hosing to SS.......Supposedly really makes a diff but for me it is just a set of seventy's brakes working...........good luck......God bless.......Dennis

Where did you send it?

 

[dennisdarrow]

You..jimmy........would ask

Golly Bud, I have slept at least twice since:

http://forums.bmwmoa.org/showthread...under-tank-troubles&highlight=master+cylinder

Racked the brain cells and Quicken reports for the answer and found:

http://www.brakecylinder.com/

Who did a great job for me at a decent price. Seems I got the SS brake lines from Bob's BMW..........Now though it appears that the folks at Sierra Specialty are retired, so a new vendor search would seem to be in order.

Wish I could help more; but this little deal came to early in the morning and long before my "TENS" unit was able to do it's remarkable job.......Anyway, that's the story and I am stickin to it............God bless.......Dennis

 

[drpetecrocker]

Thanks!

Thank you for all of the replies. I will send it off. I'm sure I could probably rebuild it myself, but at this point, it's a question of time, and I'd be pretty ticked if it started leaking on me after a short amount of time. I had no idea I could send it out. Thanks! And yeah, the location of the bike during the winter - not optimal. It's 'forcing' me to push for a new garage.

 

[roborider]

Mine was corroded and needed to be resleeved. Apple Hydraulics did a fine job.

http://www.applehydraulics.com/motorcycles.htm

 

[rogermansfield]

I just noticed mine leaking from the cap last night. I think it is the black seal ring inside the cap. Is there a source for just this ring?