R100 Rear Brake Master Cylinder

[97oilhead]

I am overhauling the brakes on my '84 R100RT. The rear disc master cylinder is being a real pain to dismantle the piston.

I have removed the internal dust cover and I am down to the washer, it soaking in liquid wrench. I have tried compressed air and tapping a rod through the brake pipe orifice with no luck.

There was a circlip in the front MC, but I can not see one in the rear. Both Clymer's and Haynes do not mention any clips etc.

Any other tips or tricks?

Thanks Nick

[SOLO LOBO]

this help at all?

[97oilhead]

I have the diagrams. I am trying to get 23 out of 1.

[bmwrench]

Inside the cylinder at the lever end is a cup washer which is an interference fit. The piston assembly is driven out by inserting a thin rod through the threaded end. I use an old spoke.

If you have a rebuild kit it will contain a new cup washer. They can't be reused.

[TINK]

I'm trying to get the cup washer out but no go. After 35 years she's in there good-n-tight.

Tried the rod through the front and tapped on it... as hard as I was comfortable, not too hard. Compressed air did nothing.

Got it soaking in liquid wrench tonight and will give her another try in the morning.

TINK

[boxerboy81]

I see a mud guard in SOLO LOBO's #2 post?

This is what you should have according to Motobins parts pix.


Max's fiche has this..


This is what I removed from my rear mc. I managed that by carefully taping it out via the small hole at one end.


Shouldn't this be in Airheads?

[TINK]

Originally Posted by boxerboy81

I see a mud guard in SOLO LOBO's #2 post?

This is what you should have according to Motobins parts pix.
[snip]

Max's fiche has this..
[snip]

This is what I removed from my rear mc. I managed that by carefully taping it out via the small hole at one end.
[snip]

Shouldn't this be in Airheads?

Thanks for the photos boxerboy81, very helpful. Yes, I purchased the kit in the first photo and will know for sure if it's the right one once I get the cup washer unstuck and the bits on the bench. Stay tuned...

TINK

[TINK]

Get 'er apart! Two days of Liquid Wrench, a piano wire rod, a swift blow with the ball peen and here we are
http://www.advrider.com/forums/showp...&postcount=222

TINK

[_cy_]

congrats on getting it apart.... up next is to see if there are any pits inside. normally there will be a few pits. key is to sand those pits out to where pits will not cut up new seals.

if pits are too deep to sand out, then next best tactic is sand edges of pits. if transition to pit can be sanded like smooth ramp for seal to glide over. most times you can save your cylinder.

if bore is too small for a honing tool. take a wood dowel rod wrap tip with medium grit emery cloth. use either spray brake cleaner or carb cleaner to degrease. preference is spray carb cleaner because no residue is left.

don't expose new seals to degreaser. dip new seals in brake fluid before trying to install.

[boxerboy81]

Originally Posted by _cy_

preference is spray carb cleaner because no residue is left.

I always thought brake cleaner was no residue, and carb cleaner was a little residue? Shellite is also a good no residue metal cleaner.

[_cy_]

Originally Posted by boxerboy81

I always thought brake cleaner was no residue, and carb cleaner was a little residue? Shellite is also a good no residue metal cleaner.

can barely see your funky color type... nope carb cleaner leaves less residues.

[boxerboy81]

Originally Posted by _cy_

can barely see your funky color type... nope carb cleaner leaves less residues.

I'm guessing you're using "fresh" for the board configuration.

[_cy_]

Originally Posted by boxerboy81

I'm guessing you're using "fresh" for the board configuration.

nope, std configuration... monitor is usually turn down low as it will go to avoid eye strain. yellow and white type are all but invisible.

edit: just tried turning up brightness on brand new Samsung 27in monitor ... type in post #11 is still all but invisible even with brightness turned way up.