Rear brake - no pressure

[bishboy]

The rear brake pedal on my R1 was able to be pressed all the way down with no effect on the brake, so I assumed it was the master cylinder so I replaced it yesterday with a second hand one from the wreckers (they assured me it worked ) but I still have no brakes.

I've partially bled the system (got interupted yesterday and I'm at work today ), fluid is coming out of the bleed valve so I assume the master cylinder is working and the brake lines aren't blocked, but the pads/pistons are not moving. The R1 has two bleed valves on the rear brake calliper (one on each side), do I bleed both just to be thorough?

Could the pistons be stuck, is it worth taking the calliper apart to check? I don't have any replacement seals etc at home, is this a problem?

I'm supposed to be going to a track day at QR tomorrow and if I have no rear brake I assume it won't pass scrutineering, I just want enough brake to pass scrutineering. Luckily I have two bikes, I may have to take the ZXR instead but was looking forward to testing the R1 out. Anybody got a rear brake calliper for a 2000 R1 laying around

[Cwidova]

i dont know about the bleed valves but i reccommend taking the caliper apart, the seal could be buggered or it could be seized. seal kits for them are cheap as and it's a easy job

[greenman43]

Could also be air at the master cylinder ; pump up the pedal, and crack the banjo bolt slightly (be prepared for a little fluid to come out) - that'll release any air trapped at the highest point of the brake system.

Cheers,
Brian