1979 xs650F build

Bleeding Master cylinders has been a topic in the forums. Search ?
Problematic at times. It has been discussed that to elevate the full caliper and brake line above the master cylinder for a period of time may actually back fill the master cylinder or at least the lines.?
Sounds like a reasonable approach .
Especially while taking a break from it.
Air in the lines is not helping for sure .
Good luck and search threads
-R
 
Could be. I usually have to be very patient with the MC. I squeeze the brake lever sloooooowly while I watch the bubbles from inside the reservoir. It can take some time but you'll be surprised by how much air you can coax out.
 
Some times I have had good luck bleeding a master cylinder by starting with nothing attached to the master and hold thumb over the outlet and pump the lever till I get pressure pushing my thumb away. Then do the same with just the hose hooked up and so on till I have the caliper on. Sometime leave the bleed screw out of the caliper and use a finger to seal it off and pump till good flow of fluid. Then do the pump hold and open till it works good.

Major note this is a messy job and brake fluid will eat paint like a paint stripper if not washed off fast so keep that in mind!
 
All good info. I'm not giving up on this master cylinder yet. I'm going to try Gary's method. I think that's his name.

Question:
How hard should it be to remove the Piston from the caliper? I'm trying to pull that thing out of there won't come out.
 

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Compressed air will pop that sucker out. But be careful, you might shoot it across the room. I put a towel in a garbage can, look the other way and let her have it. Of course most of these pistons are seized and like 50 years old.
 
Jim,
First off Gary whoever he is is an effing genius!:bow2:

Second you probably knew this but you don't want to put your finger between the caliper and the Piston when using compressed air. Because you will stop at the piston from flying across the room but your finger will not feel very good and you will frantically be looking for a way to force the Piston back into its home!:doh::laugh:
 
I stick a thin piece of plywood in the caliper and blow the piston out until it hits that. Then I remove it and place the caliper on a crumpled up rag on the floor, piston facing down. Then I blow it out the rest of the way. OK, that's step one. Now you need to remove that square sectioned o-ring seal in the caliper bore wall and clean it's groove out really well. It will most likely have a pretty good build-up of crusty, dried out brake fluid in there. When this crusty residue builds up, it forces the seal out more and the piston starts sticking.
 
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