Author Topic: LM3 Front Brake Master Cylinder Rebuild?  (Read 1312 times)

Offline Vince in Milwaukee

  • Gaggle Hero
  • *****
  • *
  • Posts: 3677
  • Location: Kenosha, WI
LM3 Front Brake Master Cylinder Rebuild?
« on: March 28, 2018, 03:09:33 PM »
From best I can tell, my front brake master cylinder is leaking.  Where exactly it's coming from has me stumped.  After a bit of riding, say 10 miles or so, there are small spots of brake fluid on the right side of my gas tank.  I was just out in the garage and cleaned everything up in that area.  I then took some toilet paper and tried various locations to see if I could get fluid on it.  No luck.  Any advice / help most appreciated.  Oh yeah, it's the round, 12mm one.   
1984 Moto Guzzi 850 LeMans III, 1986 California II
Gone but not forgotten:
1969 Moto Guzzi Ambo, 1994 BMW K75RTw/ABS, 1996 BMW R1100RT, and 1993 BMW K75

Offline dxhall

  • Gaggle Hero
  • *****
  • *
  • *
  • Posts: 1267
Re: LM3 Front Brake Master Cylinder Rebuild?
« Reply #1 on: March 28, 2018, 04:17:10 PM »
I would look for a break in the hose, particularly at the crimp.  Then I would look for a leaking seal at the caliper.  You can probably get new seals from Powerhouse in the U.K.  They advertise on eBay.

Online RinkRat II

  • Gaggle Hero
  • *****
  • *
  • *
  • *
  • *
  • *
  • Posts: 2258
  • Lake Powell AZ
Re: LM3 Front Brake Master Cylinder Rebuild?
« Reply #2 on: March 28, 2018, 04:22:51 PM »

  It won't be pretty but spritz it down with baby powder and it'll show up.

       Paul B :boozing:
A Miller in the hand is worth two in the fridge.

Online rodekyll

  • Gaggle Hero
  • *****
  • Posts: 21218
  • Not my real name
Re: LM3 Front Brake Master Cylinder Rebuild?
« Reply #3 on: March 28, 2018, 06:25:49 PM »
It might be coming from the rear seal on the piston.  Pull the boot back and see if it's damp in there.  I got struck with firewood once and it loosened a brake banjo.  I thought it was a broken line, but tightening the banjo stopped the leak.  You might get that lucky.

Offline Diploman

  • "The future just ain't what it used to be." Yogi
  • Gaggle Mentor
  • ****
  • Posts: 504
  • Location: Murrysville PA
Re: LM3 Front Brake Master Cylinder Rebuild?
« Reply #4 on: March 28, 2018, 06:45:45 PM »
You can easily rebuild the MC with this Brembo kit:

http://www.mgcycle.com/index.php?main_page=product_info&cPath=110_112&products_id=754

Better yet, you can bring your front brake up to date with a new 12mm Brembo MC with integral reservoir and brake switch built in.

http://www.mgcycle.com/index.php?main_page=product_info&cPath=110_112&products_id=1037
« Last Edit: March 28, 2018, 06:48:41 PM by Diploman »
1980 V50 II, lightly cafe'd, much modernized
1983 SP 1000 NT (Under Upgrade/Modification)
2015 KTM 390 Duke

Offline dxhall

  • Gaggle Hero
  • *****
  • *
  • *
  • Posts: 1267
Re: LM3 Front Brake Master Cylinder Rebuild?
« Reply #5 on: March 28, 2018, 07:13:31 PM »
I am surprised that a Brembo rebuild kit is available in the US.  I have read several times that Brembo will not sell kits here because they fear that a backyard guy will install one wrongly, crash, and sue them.   

Online Antietam Classic Cycle

  • Gaggle Hero
  • *****
  • *
  • Posts: 14770
  • Happily stuck in the past.
    • Antietam Classic Cycle
  • Location: Rohrersville, Maryland
Re: LM3 Front Brake Master Cylinder Rebuild?
« Reply #6 on: March 28, 2018, 07:32:45 PM »
I am surprised that a Brembo rebuild kit is available in the US.  I have read several times that Brembo will not sell kits here because they fear that a backyard guy will install one wrongly, crash, and sue them.

That seems to be true for the later ('98 on?) stuff. "Classic" stuff seems to be in good supply.
Charlie

 

***Wildguzzi Official Logo High Quality 5 Color Window Decals Back In Stock***
Shipping in USA Only. Awesome quality. Back by popular demand. All proceeds go back into the forum.
Best quality vinyl available today. Easy application.
Advertise Here