Front Brake Drama

[dmc2028372]

Evening all. Had a problem with the front brake binding on my 4rt. Brake was good but wouldn't fully release so fitted a piston repair kit and can't get it to pressurise the system at all now. No matter how much fluid I run through the system the front brake just pulls into the bar with no pressure at all..... Help!?????

[guys]

Have you tried reverse bleeding? From the caliper to the master cylinder?

Did the lever have enough play?

Edited October 30, 2014 by guys

[aussiechris]

This is probably not what you want to hear but...

I have found that after installing a seal kit you need to fill the cavities in the caliper before reinstalling the pistons. Not easy to do but if you hold the caliper at a 45° angle (with the small fluid hole at the top), then pour in as much fluid at possible which will half fill the cavity, then holding that angle, push in the piston. Some fluid should shoot out the hole when you push the piston all the way home. Do this for each piston. That way, when it's all bolted together, at least the cavities behind the pistons are full of fluid and you can just bleed the bit of air that's near the banjo fitting.

I also like to let the bike sit for a few days with the bars turned such that small bubbles can find their way back to the master cylinder. Then very carefully, just pull the brake lever in slightly just past the free play, and release. With the cover off you can sometimes see some small bubbles get released this way. Then the lever should be nice and firm.

If the system is completely drained, I'll sometimes reverse bleed using a Mity-Vac tool.

Good luck with it.

Chris.