Front Brake Rebuild

Gpaws1968

XS650 Enthusiast
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Hi everyone,

1981 Yamaha XS650 Special 2

I have to do a front brake rebuild,
  • The master cylinder and the O-ring on the reservoir need to be replaced, where do I find a replacement, it looks like a 48mm OD and 4mm thick.
  • How do I remove the brake light switch?
  • Has anyone repainted a master cylinder and calliper before?
  • My manual is useless and I can't find any decent YouTube videos
 

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There's a small tab on the switch that you press and the switch just pulls out.

The correct under reservoir O ring is mentioned here in the forum if you do a search. Note you must use the correct material for brake fluid. I couldn't get the plastic reservoir off my 1977 650 master cylinder. I replaced the entire master cylinder since the piston bore was corroded beyond use.
 
There's a small tab on the switch that you press and the switch just pulls out.

The correct under reservoir O ring is mentioned here in the forum if you do a search. Note you must use the correct material for brake fluid. I couldn't get the plastic reservoir off my 1977 650 master cylinder. I replaced the entire master cylinder since the piston bore was corroded beyond use.
Yeah I know that is has to be brake fluid-resistant rubber, thank you for the advice
 
Usually the oring is fine just lube it with some brake fluid during assembly.
Others will recommend red rubber grease.
 
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GIRLING BRAKE FLUID Resistant O-Rings and Seals

Girling Brake Fluid is also known as DOT 4 brake fluid, and is a polyalkylene glycol ether based hydraulic fluid. It is used in the braking systems of automobiles and motorcycles in order to transfer pressure from the driver's foot to the brake calipers. When exposed to Girling Brake Fluid, rubber can become brittle and prone to cracking and tearing due to its high boiling point, as well as its ability to strip away the rubber's natural oils. Additionally, prolonged exposure to Girling Brake Fluid can cause rubber to become swollen, leading to a decrease in its dimensional stability.

Recommended material type for use with GIRLING BRAKE FLUID:
EPDM (EP, EPR, Ethylene-Propylene Rubber)

EPDM o-rings, or ethylene propylene o-rings, are a family of synthetic elastomers with lower cost steam and chemical resistance, particularly for applications involving solvents, acids and other mild chemicals. Marco Rubber has the world’s largest inventory network of EPDM o-rings and made on demand custom manufacturing often without tooling fees, so the EPDM o-rings you need are always available. Whether it’s for water systems, braking systems, medical, pharmaceutical, food or dairy use, you can count on Marco Rubber to deliver your o-rings fast and efficiently.
Common Names: EPDM, Ethylene Propylene Diene Monomer Rubber
 
Just a general tip: O- rings are sized by ID x d. So that reservoir O-ring with 48 mm OD and 4 mm thick would be a 40x4mm O- ring. Or the closest equivalent. Many O-rings are slightly tight on the ID, others are right on the OD, depending on application.
 
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I've just completed front brake overhaul on my 77 650. Master cylinder was beyond repair and replaced with an EMGO 12.7mm one.

Caliper was suitable for reuse. Had to extract the piston with a grease gun and there was extensive chrome plate peeling on the piston. New 38mm piston in stainless steel is pretty cheap. Easy job once the thing is apart. New piston seal, new bleed nipple etc....readily available and cheap.
 
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