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Discussion Starter #1 (Edited)
I bought a 2005 DS 1000S off craiglist that the previous owner laid down on the right side in his driveway. The rear brake was not working when I bought it. I brought it into the shop to get new tires and have them take a look at the rear brake to see if it was an easy fix. They suggested replacing the parts in the attached photo (Master Cylinder). I replaced these and then bled the brakes until the fluid coming out was clear with no air bubbles. Method I used to bleed the brakes; I would fill the reservoir, pump the lever a couple times, hold the lever down, open the release at the end of the brake line and then close it. The rear brake lever still goes all the way down like the brakes haven't pressurized if that is the right term? Any thoughts on what might be going on here?

Thanks!
 

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Hi,

Your method for bleeding is fine, perhaps a defective master cylinder...It's happened to me before.

L8tr
Pete
 

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...or, it may still have some air in there. When you were pressing the lever down and opening the bleeder, did you see bubbles in the fluid? You said you pressed the lever down...before you opened the bleeder did the lever bottom out or was there some resistance?
 

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So you think the one that I put in might be defective?
Unlikely the new master is defective. Bleeding these brakes is a pain where the sun don't shine at the best of times. I'd modify your bleeding protocol so that you open the bleed port BEFORE squeezing the lever. Open - squeeze - close - release. Have a piece of clear tubing on the bleed nipple running into a jar. The level of fluid in the reservoir should drop and fluid should start flowing out of the bleed nipple. Stop when no more bubbles come out of the bleed nipple.

I've had issues with this, particularly on bikes where the brake caliper is underslung, i.e. it hangs down off the bottom of the disc. The bleed nipple needs to be at the high point of the caliper or you will never get all the air out. What I have found works every time is to attach a 50cc syringe to a piece of tubing which is connected to the bleed nipple. Fill the syringe and tubing with as much brake fluid as you can and use as short a piece of tubing as you can. Zip-tie or hose clamp both ends of the tubing. Open the bleed nipple and push the fluid through the caliper into the (cap removed) reservoir until no bubbles. Close the bleed nipple, put the cover on the reservoir, you're done. Make sure not to let the reservoir overflow as brake fluid will take off paint and ruin plastic and carbon fiber very quickly. It will also etch metal, i.e. your engine cases and/or frame. You can remove excess with a smaller syringe.
 

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Thanks for the tip! I've been trying to track down the cause of my rear brake issues and hadn't thought of bleeding them that way.
 

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shorten the pushrod a lot, so that you get freeplay. a lot of it. i say this a lot, and often people get really pissy about it because it sounds like i'm stating the obvious, but if it has no freeplay it will never bleed. and sometimes what feels like freeplay is just piston movement against no pressure.

if you take the return spring off it makes it very obvious if there is freeplay or not, or take the pushrod pin out and see if the pushrod tries to push back past the lever.

of course, this might not have anything to do with your issue, but it's a one minute test and if you don't rule it out you're never going to make it work.
 

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If your brake caliper is underslung it will need to be removed and put up on the top of the rotor. At least that is what needed to be done with my monster.
There is a you-tube video on this procedure.
 
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