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08 rear master cylinder problem

4K views 21 replies 7 participants last post by  flycbr1000 
#1 ·
Hey guys. Posted up about this before but can't really find a definitive answer, plus got some weird flack from a certain vendor for daring to ask a question related to a product that I didn't purchase from him (that was a first...).
Anyway, right after installing Vortex rearsets, my rear brake lever is way low and nothing happens in terms of brakes. Bled the system multiple times-nothing. I think I turned the rear brake adjuster too many times and now its just done.
Any ideas? Should I swap a master cylinder out with a new/used one? Are those rebuild kits any good? Anyone have this problem? The lever travel is super far so I was thinking just move them up but shouldn't they be "adjustable"?... Will moving the adjuster too much break the master cylinder? I went too far beyond the range of half an inch or so in an attempt to fix them, but obviously did damage instead.
Any advice and suggestions/guidance would certainly be appreciated. Although I hardly ever use the rear brake, I like all my stuff to work properly, and a working rear brake is required for tech at the track. Thanks in advance guys...
 
#2 ·
Anyone?..... Use the search?...let me try that again. No one encountered this or even something similar? Guess I'm the only dipshit that can screw up such a simple bolt on mod!...lol...can't figure out what went wrong where...smh.... Guess I'll just buy another rear master and see what happens....
 
#3 ·
Hey man...youre not the only one haha. It happened to me also. I had to bleed the line for a good while before I was able to get some sort of pressure. With having a steel line I tought it would help with more pressure but the opposite ended up happening. The brake foot peg has to be pressed low and fiercly to allow for descent braking on my bike now. Its not how it should be but I didnt know what else to do to get it to how it should be. I have the Gilles rear sets on the bike.
 
#4 ·
^^^^Thanks for the reply. I can't figure it out either, but I will take your advice and try bleeding the crap out of them again. Weird how there's no real answer to this problem...although we have different rear sets I know you have the same issue...the solution should be the same. I don't understand the dramatic drop in the pedal except that they are that totally different from stock. Maybe moving the bracket around but that would render them not adjustable so what was the point, right? I don't know....I'll keep trying...thanks again.
 
#6 ·
^^^Thanks for joining the conversation... Now its an issue with even newer bikes apparently. Sorry to hear. All I'm getting so far is bleed the brakes. I'm getting a new/used m/c and I'll tell you how that goes. Still asking around and searching the internet, etc. There's gotta be an answer!....
 
#11 ·
I had the same problem when I switched to a set of SS Galfer lines. I swear I must have followed 1/2 dozen different methods for bleeding the brakes, starting with the video on Galfer's website. Nothing seemed to help.

The front brake lever would still come to within 1" or so of the grip before the brakes would start to grab. The rear brake was always fine. I just more or less got used to it the last few months of last season before I put it away for the winter.

A few weeks ago I installed a set of speed bleeders for all 4 bleed nipples. I started out with a Mityvac at the left front caliper, then the right front, then the MC. After that I just used a clear tube and relied on the speed bleeders, slowly pumping at each bleeder until I was absolutely sure there was no air coming through the line. Then I moved on to the next bleeder and did the same.

After I finished, the front brake lever finally returned to its old self, where the pads start to grab right after the clicking sound of the brake switch. I'm happy but it was a hassle. I only installed the SS lines for looks and I'm not sure if all the effort to get it right was worth it.
 
#12 ·
Thanks for sharing Tedebear^^^... I keep reading that the Mightyvac is the way to go to really rid the system of any air.... My bike is stored at my sisters house which is far from me but as soon as I get a chance I'm going to bleed them properly and maybe borrow a friends Mightyvac... I will probably reassemble the whole brake side rear set and do everything step by step to see if I can get to the bottom of this.
Thanks to all for sharing your insight... Will post results...
 
#13 ·
So yesterday I ended up switching my Gilles rearsets from my 08 to my 09. I noticed that on the bottom of the master cylinder it unscrews to adjust to hook into the linkage on the rearset. By adjusting this it drastically helped reduce the lever freeplay and is holding solid pressure.
 
#14 ·
^^^^Thanks for posting. That is where I might have gone past where the adjustability ends. Went too far and now I can't seem to get it right. Still haven't had time to get the bike.
This issue seems to be very wide spread and not limited to CBR's. I have read about the exact issue with many different manufacturers. The main issue is bleeding. I hope that is my problem; air in the system as opposed to a broken master cylinder. Most people with a solution got rid of the air a few different ways...Mighty vac...reverse bleeding...even bleeding at the master cylinder by removing the banjo bolt (not exactly clear how they did that one...in one instance the person simply added brake fluid straight into the master cylinder) and some people have been successful by using a syringe to push brake fluid from the caliper out through the master cylinder. Some have said to bleed and zip tie the brake pedal closed overnight to evacuate air, while others simply stated that they got it "professionally" done.
I plan to try a few of these methods and hope it works out. Keep you posted.
 
#15 ·
So Im not sure what happened to cause this but thankfully it didnt happen on the freeway. I rode to work and the bike was fine. No issues what so ever. On my way home that was a diffrent story. While riding on the freeway I started feeling the bike sluggish when releasing the throttle. It was slowing down drastically. So I exited the freeway and as I was coming to a stop the rear brake locked up completely. My rear master cylinder was engaged all the way. The rotor and pads were smoking. I had to unclip the rearset to the master cylinder to be able to move the bike.
Once I was in the garage i readjusted the screw on the master cylinder and linked it up to the rear set again, but sadly had the same problem AGAIN. Little pressure and lots of travel in brake lever. This is with a stock brake line. WTF?!
 
#16 ·
^^^^ Wow!... Glad you're ok. This is getting dangerous. The problem is wide spread. I'm guessing the manufacturers don't want to make these rear master cylinders too powerful so that this kind of thing doesn't happen, but by going cheap they've created more problems... I'm not even sure if it's that they're cheap...some Ducatis and Aprilias with Brembos even have problems. Whatever the issue, it's widespread and dangerous.
At any rate, I've scoured the Internet and have decided (once I get time off from work!) to bleed the brakes by using a few different methods to see what's going on. I suggest you break down yours as well step by step to try and get down to the bottom of this. Sorry I'm not much help... My rear brake doesn't even work... Glad you didn't get hurt and good luck. If you don't work on your bike maybe a trip to Honda or a good shop is in order. That's a serious safety issue and you need to sort it out ASAP.
 
#17 ·
UPDATE- rear brake issue

Had this problem since last season. After installing Vortex rear sets, my rear brake didn't work and I couldn't bleed them. Finally, I bought a used master cylinder from eBay for 20 bucks. I switched out the master and I added some Motul fluid. I used a tube with a one way valve that I got from eBay.
I connected to the bleeder, cracked it open and started pumping the brake pedal. At first, nothing really. I kept in mind what many of you guys suggested...like it might take some time.
So I kept at it. Slowly the fluid started coming through the tube into the Gatorade bottle I used to catch the old fluid. Someone here suggested pumping the pedal with the bleeder screw closed. I tried that and as soon as I opened it up again a whole lot of fluid came through with a lot of air bubbles. Kept at it, every now and then closing the bleeder screrw pumping, opening it back up and pumping away. I also tapped on the brake line at the high point from time to time.
Ultimately, I started seeing no bubbles and getting pressure at the pedal. At the end, the rear brake is super solid, and no return spring needed, the pressure is awesome. I think my master cylinder might have been bad. So if anyone is having this issue, get a used master off eBay and bleed away!
Thanks to all for the advice and if there's any way I can help anyone with this particular issue, just hit me up!
 
#19 ·
I never use my rear brake but I lke to know its there if I need it . Right now Im having the same problem . I just changed tires so I always just bleed the brakes . Now no pressure . I know I can figure it out just a pain .
One thing everyone needs to remember is to NOT fill the resivor all the way to the top and put your cap on . Your breaks will lock up.
 
#20 ·
One thing I learned from fixin cars. Hondas MC is a big pain to bleed. Prob tolerances are too tight, so same thing when installing rcs 19 MC. It took lots of effort to bleed it before fluid started to flow. Had to struggle with the bleeding for more than 30 mins. Remembered the old trick, let the fluid sip in slowly for like 15 mins and re bleed again, after a while then it started to flow

I would start bleeding from mc again before make decision to replace rear mc.

Replaced my rear line with spiegler ss, rear sets, oem pads and mc, it didnt really give me a hard time, but i started from mc first.
 
#22 ·
Lol.... Yeah, that was a while ago! At the end I replaced the stock rear master cylinder and just bled the brakes. It takes some time but it will work.... Patience and a one way valve bleeder tube off eBay and you're good! Never had a problem since and I still have the same bike. It might take quite some time, just be patient.
 
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