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Rear Master Cylinder Crapped Out

Started by NorDog, March 09, 2011, 12:49:36 PM

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NorDog

March 09, 2011, 12:49:36 PM
I bought my S4RS new in '07.  About a 18 months ago the dealer replaced my rear master cylinder under warrantee.  There were no apparent leaks, but it just wouldn't actuate the rear brake for anything more substantial than holding a stopped bike in place on a slight incline.  There is a lot of travel in the brake lever before there is any resistance, and then just a little bit of grip at the disk.

Now the "new" master cylinder seems to have crapped out again.  That is to say that there are the same symptoms and no apparent leaks.

Are the rear master cylinders a chronic problem the way the plastic fuel tanks are?
A man in passion rides a mad horse. -- Ben Franklin

ducpainter

#1
March 09, 2011, 01:12:06 PM
Some of them were. I remember that 999's had the same problem.

I thought they had it squared away.
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
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    is even more amazing than yours."
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    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."


Speeddog

#2
March 09, 2011, 01:14:24 PM
The S*R brake setup is notorious for going soft.
They're very difficult to bleed effectively.

Some of the '05-'06 vintage black master cylinders were flaky.

But I've got an '06 S2R1k here that's got a soft lever, and it's a gold master.
- - - - - Valley Desmo Service - - - - -
Reseda, CA
(951) 640-8908

~~~ "We've rearranged the deck chairs, refilled the champagne glasses, and the band sounds great. This is fine." - Alberto Puig ~~~

NorDog

#3
March 11, 2011, 08:54:06 AM
Quote from: Speeddog on March 09, 2011, 01:14:24 PM
The S*R brake setup is notorious for going soft.
They're very difficult to bleed effectively.

Some of the '05-'06 vintage black master cylinders were flaky.

But I've got an '06 S2R1k here that's got a soft lever, and it's a gold master.

Do you think bleeding the system will help?  Or is it likely that the master cylinder is shot?
A man in passion rides a mad horse. -- Ben Franklin

jerryz

#4
March 11, 2011, 10:18:07 AM
bleed it using a syringe and short hose so you can force the fluid thru from the lever and keep filling the reservoir  the syringe will auto fill and all air will be out ...this is the method I have used for years .

Speeddog

#5
March 11, 2011, 10:47:46 AM
Quote from: NorDog on March 11, 2011, 08:54:06 AM
Do you think bleeding the system will help?  Or is it likely that the master cylinder is shot?

Give it a good flush and bleed, see if it holds up.

Replacement masters are just a bit over $50.
- - - - - Valley Desmo Service - - - - -
Reseda, CA
(951) 640-8908

~~~ "We've rearranged the deck chairs, refilled the champagne glasses, and the band sounds great. This is fine." - Alberto Puig ~~~

He Man

#6
March 11, 2011, 06:20:12 PM
they are upside down on the S*R bikes, take them off and try to bleed it that way.

Gimpy

#7
March 11, 2011, 09:45:48 PM
I've experienced similar symptoms, but after my 2nd rear master cylinder I found I was dragging the rear brake a boiling the fluid.  Now I'm a little more careful in my foot placement and I change the fluid in the rear master when I do the oil.   [thumbsup]
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