Rear brake master cylinder

[ArchRider]

First a little history.  Due to a previous owner not changing fluid often enough, I have had a bunch of work done on both front and rear brakes including having the rear brake caliper rebuilt.  Recently the rear caliper started hanging up again to the point where more than once I had to heave it out of a parking space (not easy, as I'm sure you all know).  I spoke with some guys at the dealer and they suggested it may be the master cylinder so I got a rebuild kit and to my surprise, it was rather easy to rebuild (didn't want to spend $90/hr labor).  Now, I've bled the system 3 times but the travel on the pedal is still excessive.  With my foot, I can't push it down far enough to get the brakes to grab.  I can however, get it to grab in the garage if I just push it down with my hand.  When I took the clevis off the lever, I counted the exposed threads so I knew where to set it so I think I have that correct.  Has anyone ever had this problem?  If I run the clevis nut down to lift the lever, will I be risking some other problem?

[Timbox2]

My pedal is similar, in fact I have had to drop my pedal lower as I fitted Touratech Footrests, but as you say, there is a lot of travel before it really bites, cant think of any reason why lifting the pedal would cause any probs though.

[cosmo]

Make sure the relief hole is uncovered when the pedal is released, else the brake will remain 'on', and will get tighter as you go. NOT a liveable solution!!
Usually you will need about a mm or two clearance twixt pushrod and piston and you'll be OK.

Cosmo

[Mustang]

Sounds to me like you still have air bubbles in the system ..............

these work incredible and takes about 2 minutes to completely refill an empty brake system with fluid and no air bubbles .'Auto Zone has em for around 30 bucks
this one is from northern tool and is 42 bucks , money well spent .

[katoomon]

Agreed, even though the system has been bled 3 times, it sounds like there is still air that will not bleed out.  The vacuum pump picured above comes out every time I do brakes.

Another option is to back fill "back bleed" the hydraulic system.  Go to a feed store and get a large syringe, no needle, put appropriate sized clear tubing on the syringe (so you can see what is going on) and fill the system from the bottom up pushing brake fluid through the caliper bleed nipple.  This will push air up and out the reservoir as you back fill.

Obviously, or maybe not so obvious, you need to drain or remove all the brake fluid before you attempt this method or you will not know if you have pushed brake fluid through the entire system; moving any air up and out as it back fills.  Use the drained fluid as a volume estimate for the syringe size; the syringe needs to be large enough to fill your hydraulic brake system without stopping to add more brake fluid. If you were doing your front brake, you may have to add more fluid (slightly tricky) to the syringe, but no air bubbles through the bleed nipple once you start.

[ArchRider]

OK.  Thank you all for your replies.  I was thinking the same thing as most of you, that the air has not been bled all the way out.  However, I am using a vacuum pump and after three times I figured I would have it all out by now.  But I will try again.  I have also noticed that while I counted the threads on the rod before i took the cylinder apart, with relation to my foot on the peg, the pedal seems not as high as before .  So, I'm thinking I also need to drop the clevis which will raise the other end of the pedal.
Which leads me to ask Cosmo, which relief hole are you talking about?  When I took the master cylinder off the bike, I don't recall seeing one.  Can you describe the location of this hole?

[Dev_1]

Aaaand 6 years later, I get to share this seemingly common issue. My rear brake is seemingly useless and does hold fair constant tension on the rear disk.
:icon_scratch:Did the pedal adjustment work out for you? Did you reverse-bleed the system? Where is the relief hole?

Thank you all in advance :D

[Bixxer Bob]

The tension at the disk is a separate issue.  I have the same and need to sort it but don't have the time at the moment.  It will be either binding of the caliper slide pins, cruddy pistons (only replaced last year so not likely).  I'm puzzled by the "relief hole" ....  fluid goes from the master cylinder to the caliper when you push the pedal, and back to the master cylinder from the caliper when you release.  Perhaps it's crap on the caliper side of the master cyllinder outlet that blocks it when the fluid flows the other way.

I also had your bleed problem after changing the pistons.  Take the caliper off and hold it above the level of the master cylinder with the nipple uppermost so you get all the air out.

In normal use, the Tiger back brake locks the rear wheel quicker than any other bike I've ever had.  The lever travel is minimal.

[Dev_1]

Great info Bixxer Bob. I'll look into setting her right.

[Bixxer Bob]

By slide pins I mean the pins that retain the pads, but also the one that half the caliper rides on. Remove the rubber seals and give eveyrthing a good clean and grease.

[Dev_1]

Finally rebuilt my rear calipers last weekend. I actually have some caliper squeeze now! ....now only if I could raise the lever up a bit and maybe move it closer to the rearset...

Looking to do a double banjo bolt straight to caliper setup in the front, but having trouble finding the right bolt and brake line. 

[Timbox2]

Finally rebuilt my rear calipers last weekend. I actually have some caliper squeeze now! ....now only if I could raise the lever up a bit and maybe move it closer to the rearset...

Looking to do a double banjo bolt straight to caliper setup in the front, but having trouble finding the right bolt and brake line. 

With the Banjos, cant you just swap them around? IE: use the double from the caliper up at the Master and vice versa, youve gotta have somebody near you that can make braided hoses to length, and again maybe you only need 1 extra for the R/H caliper. I could be talking b***x mind you

[Sin_Tiger]

You're nearest HEL dealer will make the pipes up to size, handy if you've got bar risers. They'll most likely keep the double banjo bolts in stock as this is quite a common mod. Don't forget the extra sealing washers  :icon_wink:

[Dev_1]

I think Timbox has the right idea