master cylinder

[Rebel]

It seems like one thing after another. I got my caliper rebuild kits, and have not been able to fully "bleed" the system since. I presume the o rings in the master cylinder. I am getting only fluid out of the bleeder on the caliper, and the brakes ARE working, just very soft and spongy on the brake lever. Anyway, I just wanted to vent, I have just installed new throttle cables, calipers, fork seals and STILL can't ride!

[Rob]

All I have, is when I rebuilt my brake system on my R65, I overhauled it as a "system". Caliper, new line, and rebuilt the master cylinder. You can't leave anything out. Weakest link dept.

[ME 109]

Some folk like to reverse bleed troublesome systems by using a syringe or similar to pump brake fluid into the bleed nipple on the calipers. Lid off the master cylinder, and remove brake fluid from the reservoir as required to prevent overflowing.

Others like to pull on the brake lever, release bleed screw and hold lever against bar, nip up bleed screw, and tape/whatever the lever to the bar. Leave overnight, works for some.

[Rebel]

Thanks for the replies. I have tried fluid injection from the bleeder and the other method with a strap overnight on the brake lever, both to no avail. I presume at this point the o ring in the master cylinder is not sealing producing proper pressure.

[SteveD]

Frustrating isn't it!.

Try it again, alternate the methods. It can take a few goes. Try pushing the pistons into the caliper to reduce the volume. Inject the fluid slowly, tap the caliper regularly with a mallet. It can be a pita. Leave it overnight with the brake lightly on.

[Rob]

Did you disassemble the master cylinder and inspect the bore for any irregularities?

[George Ryals]

Reverse injection of the fluid only works if you orient the caliper so that the hose connection is upper most. Normal configuration is that the bleeder is upper most so air(rises to the top) can get out of the bleeder connection.

[Rebel]

Problem resolved. New master cylinder took care of things!!