Rear Brake Rebuild

[lumox]

Gave it a shot with the screw driver, seals didn't move at all. So off to Trooper Lu workshop in Moorebank, 10 minutes and $25 later, seals out and new in. Couldn't be happier.

[Christian Raith]

Some rag on the edge of the tube and a screwdriver to lever them out. Just don't scratch the inside of the tube.

[lumox]

Thanks guys. Got the fluid through the lines all good. Another problem down not many more to go.

Any idea on how to get the fork seals out?

[makzy]

Peter is rite, bleed the master cylinder first, when i do mine i remove the master and hold it up high and use a short fat phillips screwdriver as a push rod, and have a mate do the bleeding at the calliper, then fit it all back up and do a final bleed, hasn't failed for us..

[petejw1966]

if you've rebuilt the master cylinder
you need to bleed it first.
usually best done on the bench
but if u have it fitted u can also do it on the bike
just get plenty of rags and cover any painted areas first,
remove the hose and place your finger over the outlet
press the lever you should feel air/fluid coming out, keep your finger
over the outlet and press a Cpl more times till no air comes out,
then reconnect the hose and bleed the caliper, if at any time you run
out of fluid youll need to rebleed the m/c again.
hope that helps.

[Jonesy :-)]

lumox,
If your seals are in good order the piston will re-load instantaneously, a count to 5 would only be needed if the brake fluid was the viscosity of honey. I agree whole heartedly with the rest of Jeffs method though. Bleed nipple open, pedal down, bleed nipple closed, pedal up
In case of an air lock and repeated un-successful attempts to bleed (like you describe) a little positive pressure in the master cylinder reservoir will get things happening.
If that don't work the little piston cup seal doodad thing might be back to front, basically working in reverse and sucking (air, most likely) out of the brake line and discharging into the reservoir.

[excess.11]

Jonesy.........it certainly does work due to viscosity and the slow refill in front of the plunger.....allowing time to refill inbetween pump down allows a reload of fluid......first hand experience tells me it does.
I would also first make sure after a rebuild that the plunger shaft is adjusted up into the master cylinder piston and nipped with lock nut before starting. Check the piston is returning inbetween strokes.
Whether the fluid is forced via pressure or time allowed for gravity feed....either method should work.....its not rocket science....just need to have fluid in front of the plunger before the pump down.

[Jonesy :-)]

try adapting this idea to the rear brakes.
guaranteed to work if the master cylinder is rebuilt properly....... counting 5 between strokes isn't going to help

http://xs1100.com.au/forum/index.php?topic=1497.0

[excess.11]

Lumox ....when bleeding the back brake..........many people make the mistake of  repeatedly pumping the pedal .............and wondering why no fluid is being pumped through the bleed nipple.
 
The reason why...... is best explained when comparing bleeding the front brakes to the rear.
When bleeding the front brakes.......you have a vertical brakeline...from the master cylinder which allows gravity to assist in bleeding from the master cylinder all the way down to the caliper pistons .

With the rear brake setup........If you look at the rear master cylinder in relation to the rear brake caliper...they are horizontally in line with each other ...........gravity "IS NOT" going to assist you here .

As long as all your plunger seals and brake components are in good order.........you " MUST" allow a "SLOW" count of "5" inbetween each push on the brake pedal to allow the fluid in the master cylinder to "RELOAD" in front of the plunger before the next push.
Obviously have the nipple open on the push down phase with a clear tube attached into a half filled jar of fluid.....and while holding it down..... close off the nipple......then release the pedal................count to "5" slowly..then repeat.
This will inject a small amount of fluid each time you carry out a pump down.....and will result in fluid being slowly pushed along the line and filling up the piston reservoir.
You shoud see bubbles in the jar of fluid on each push.......if not.....you most probably need a new set of rubbers seals on the plunjer in the master cylinder.

Repeatedly pumping at a quick rate....... will result in pumping and sucking a small amount of fluid virtually forwards and backwards........ with out allowing extra fluid to flow down in front of the plunger for injection into the line.
It s like the Tortoise and the Hare......"slowly but surely ....will win the race.

Many people have been frustrated with bleeding their brakes and coming up with pressurizing the master cylinder..or other ad hoc remedies....when all they had to do was either fit a new master cylinder kit......clean out nipples .....clean out the piston reservoir and seals at the caliper and simply allow time inbetween each push.

[lumox]

Okay what am I doing wrong?
Rear brake master cylinder has a new kit installed. Cleaned out the lines, new brake pads. Issue is, tried bleeding the brakes, made sure there was fluid in the lines,  but I can't seem to be able to build up any pressure. Keep pumping (Not humping) no fluid runs through.