My mates rear brake on his '09 Beta Evo suddenly locked on today, lever was still up in the off position, we let a bit of oil out and it freed up for about 10mins before siezing up again, done this a few more times so we stripped down the master cylinder and cleaned it all (seals looked OK), rebuilt it and same happened again after 10mins riding, so again we let a little oil out and that seemed to have done the trick, it lasted all afternoon. So I have a couple of questions:

1. What caused this? I'm guessing it's something to do with pressure building up after so many pumps of the lever and somehow not releasing.

2. What's the correct way to bleed the rear? Not having done a rear before I connected a power bleeder to the nipple on the caliper which forced fluid up into the system which I then bled out by loosening the banjo bolt on the master cylinder until the air was out. When I use the power bleeder on the front brake I attach it to he master cylinder with a cap I made, force oil down the system and bleed it out of the nipple on the caliper which works great but obviously the rear does not have a cap to attach the power bleeder to. What I did to the rear did actually work just wondering what the correct method is?

Could there be some debris in the system acting like a non return valve, I knew of an internally collapsed hose on a car that did his.

I much prefer a vacuum bleeder on the calliper bleed nipple. I have seen forced reverse bleeding cause problems when dirt / debris (I know there should not be any but often is) are forced back up into the hoses and master cylinder.

Edited June 21, 201412 yr by dadof2

common problem and is usually caused by the rear pads being worn at an angle, or worn too far down causing slave piston/s to stick in the "on" position, which causes the fluid to boil, which jams the brake on

Hmmm. Learn something new every day.

Thanks :-)

check the master cylinder cap there is little breath holes in it they could be blocked also make sure there is enough play in the pedal

I have found that if I don't have enough free play in the rear brake lever that after 5 or 10 mins the brake over heats, and binds so bad that as you pull the clutch in to change gear the rear wheel locks up on grass.

Nelly you are too quick for me at least we are on the same lines cheers.

check the master cylinder cap there is little breath holes in it they could be blocked also make sure there is enough play in the pedal

What cap?

I have found that if I don't have enough free play in the rear brake lever that after 5 or 10 mins the brake over heats, and binds so bad that as you pull the clutch in to change gear the rear wheel locks up on grass.

Will check that also, thanks :-)

The master cylinder cap is where you put the brake fluid for the rear brake usually near tank, follow the brke pipe from the the pedal upwards.

The master cylinder cap is where you put the brake fluid for the rear brake usually near tank, follow the brke pipe from the the pedal upwards.

Ah the reservoir, yeah thats all clean :-)

Check the bolt that holds the brake lever on isn't tightening up as the brake lever is continually pressed, this gives the same effect/feeling as a 'sticky' brake. Had this happen on my 10 evo, a dab of locktight sorted it out.

Hope this helps.