Bleeding the rear brakes (again...)

[jboothe]

Ok...really...what is the trick? This is just stupid!! A little reservoir, a very small master cyclinder, a short piece of line to the one piston caliper. I have removed the caliper, used a vacuum type bleeder, tried the old method, I've run enough new brake fluid thru this thing to bleed six cars...

I was searching and found this. Sounds like Pedro had exactly the same problem. Any resolution? Please help if you can. I am heading to the track Saturday morning and not that I actually care if the rear brake works (unless I run off in the grass) but I may not pass tech...

Originally Posted by PedroHM

First off I can tell you that on the STD Hyper, adding EBC pads, good fluid AND a Brembo RCS19 master makes for 1 finger braking goodness! I can't believe how smooth and linear the braking is now and you can even feel the pads warm up when trail braking for a decent distance and feel it all in the lever! The RCS19 is also a direct swap over, the stock brake light switch just clips onto the master and the banjo will fit with a bit of a wiggle.

secondly..

HOW THE FU(K do you get pressure in the rear brake!! I bled it out by pumping fluid through and just kept topping up the res until the fluid coming out was clean and green (green fluid), after pumping and pumping I can't get any pressure back in the system, I've tried the caliper off hold it up and bleed air out the nipple, I've tried cracking the banjo to let air out the master, I've tried totally emptying and pushing fluid up via the caliper to fill the res up (this worked the best) but still can't pressure in the lever. Its working just but will only grab righ at the bottom of lever travel.

[AXE]

Pull caliper raise above master cylinder zip tie to frame bleed from there.

[jboothe]

Originally Posted by AXE

Pull caliper raise above master cylinder zip tie to frame bleed from there.

Thanks AXE. I have tried that and about everything else. I did PM PedroHM and he did get his done. It just takes time, a lot of fluid and apparently luck...

[stryder]

Remove some fluid out of the reservoir, remove caliper, push pucks back in, remount caliper, see if that works.

[ProTwinSteve]

are you getting a soft lever after riding or it just goes soft over time, sitting, NOT riding.
Heat can affect the fluid, try motul RBF660 its high temp stuff and its pretty darn good.

If it just loses lever sitting over time, replace the master.
cheap cheap if you look around. make sure though if you do replace the master, give the lever anough free play other wise you will have the "other" rear brake problem.

let us know how you go.

[buggsz24]

I flush my brake and clutch lines in a ridiculously little amount of time using this tool, no moving calipers, not mess, and fast.


http://www.motionpro.com/motorcycle/partno/08-0316/

[jboothe]

I think I understand the issue. It's mostly because its a very small master cylinder and its moving a very small amount of fluid. Any amount of air will collect in the corners of the caliper, bends in the line, top of the master banjo fitting, etc and cause problems. My issue came up because I flushed the fluid over the winter and had no real problems however I must have left a tiny bit of air at the top of the reservoir trapped around that upper diaphram hidden in the folds. After doing a couple of track days and resulting Gs, lean angles, vibration, etc the air was able to work it's way in to the system. Yesterday afternoon I went to test ride the bike after replacing the chain and noticed that I had almost no rear brake.

Any way I am going to go buy a gallon of fluid this afternoon after work and screw with it till its done. I have tried all the usual tricks and removed the caliper and hung it, tried a vacuum bleeder, tapped on all the lines, caliper, master cylinder, tried to precharge the master, etc etc etc...

I have to leave for the track at 6:00am tomorrow and if I haven't got it by late tonight I may drag the damn thing out of the garage, douse it with gasoline and light it up. If I do, I will take pictures to post here...

It just pisses me off because it such a simple system. I have been an aircraft mechanic all my life and have taken apart/rebuilt/repaired/ cars, motorcycles, aircraft and boats over the years and this is just frustrating.

[CamDLux]

This is the method I used on my Aprilia. KZMille Guide to Brake Bleeding a Brembo. In short, remove the caliper and reverse bleed reposition and reverse bleed again.

[jboothe]

Thanks for that info. I did get it finally. I had the rear caliper hung on the side of the bike doing the traditional method and rapping on the caliper, master and line for several mins when all of the sudden a bubble popped out and into the clear line. I continued bleeding for several more reservoirs full of fluid but that seeed to do it. works much better now.