I have no brakes in the back. pressure is almost non-existing on pedal, it goes all the way down without providing any stopping power. I'm new to cbrs and don't know if the calipers are supposed to move around a lot (free floating brakes) or if there are parts broken/missing. Next thought would be my brake master cylinder for the rear. Front brake works great. Anybody know about this and how to troubleshoot and fix it? The bike is new to me, so any help would be great! Thanks

 

Start with a fluid swap, sounds like air in the lines. Just keep adding fluid at the MC,
pump on the pedal several times and then hold it down, crack the valve open to let
fluid flow out through clear tubing into a jar. The end of the tube should be below the
surface of the fluid in the jar. This will prevent air from being pulled, back into the system.

Close valve, release pedal and then do it again and again...

After a time, you will see the fluid get clear and clean and the pedal will start to
stiffen as you pump it down. I will get it to stiffen up and then re-visit it the following day.
That gives time to allow any agitated bubbles to surface and float to the top.

It will allow you to be more through and successful on the second pass.

You should also consider, re-packing the boots for the hanger bolts,
those little accordians, where the calipers are mounted to the bike.

Good luck, Ern

 

I already tried bleeding the lines before this post, guess I forgot to mention that. After many attempts the pedal was still going all the way. I did it the way you suggested probably about 6 times with no change. That's what led me to look into other problems other than just air in the lines. Could this be from the caliper moving too much, or should I look into the master cylinder?

 

Even if there is air in the system it should pump up some. Unless the fluid in the resevoir is blocked from getting to the mc. If you can't get any pressure and there are no fluid leaks at the mc, hose ends, or caliper, you need to rebuild/replace the mc.

 

Yuppers, thinking the same as gpfan, with the added note that I would go ahead
and replace the caliper piston seals, as well. That will put the entire system on an
even footing, for the negligable cost of the added seals, and save another tear-down, if that's where the problem lies, instead.

You also might consider upgrading to a ss line while you are doing the rest of the
work. After that, you should only need to re-visit the system for fluid changes and
re-packing the hanger-pin boots, in future maintenance.

Hope this gets you back in action, Ern

 

Unrelated to your fix. Who needs the rear brake besides rossi and the boys who like to ride off into the grass every now and again. You would be amazed at how well the front brake stops when applied smooth, slow, without jerky pulling.... in the sun and definately in the rain.

 

I agree that the front brake accounts for most of my braking. But you can't tell me the rear brake applied with the front brake won't stop faster. I live in California and deal with people not paying attention on the daily. So as to keep from flying over the hood of someones car I feel better about fixing it.

 

Using the rear brake is common practice in MotoGP. Some riders more than others. Nickey Hayden has a larger rear brake than Valentino because he uses it to back the rear in. You can feel the effect of using the rear brake to tighten your line in a turn better without the standup effect of using the front brake mid turn. Just be careful until you get the hang of it.