Brakes failing

[elbrownos]

My rear brake is conking out on me.
In the last couple of months it's gotten very weak and spongy.
As I ride in winter, I figured one of the pistons has siezed as usual.
So I pulled it off and cleaned the pistons (they didn't seem to be siezed after all) and put it back on.
No difference, actually if anything a little worse.
So I figure it must be the hose getting weak and bulging (it's original). Put a new HEL braided hose on last week, bled the system.
No difference, actually if anything a little worse.
So that leaves two options. Either I really do have air in the system, or the master cylinder is knackered.
What are the chances of the master cylinder being worn out? It's a 2002 model with 20k miles.
I figure I can test it by removing the hose from the output of the master cylinder and plugging the port. If it's still spongy then it's the master cylinder, if it's firm then it's air. Will try this on the weekend.
Is it a better option to buy a used master cylinder off ebay or overhaul my own? Not that I can even find an overhaul kit. Any tips?
Cheers
Elbrownos

[Kentish]

Did you remove the pistons completely and check the seals?

[elbrownos]

I replaced all the caliper seals and pistons last April

[red98]

what bleeding method are you using ?

[Punkstig]

No need to swear at the guy Red!

[Exupnut]

what bleeding method are you using ?

I agree punkstig.. That's bleeding terrible language.. Hope I'm not that grumpy @ 98.

[Paul]

I've got a 2001 fazer, I've had it from new.


My back brake has been crap from new and I've bled it several times.


And then I think to myself do I think it's crap because I compare it with the front brake?


In any event you should be able to get the back wheel to lock up in the wet.
If you can't then there is something wrong with it.

[risticuss]

I put HH pads in my rear brake and that seemed to help with overall bite a feel.... and I can now feel it slowing me down if I use it with a steady throttle.


Did see a thou caliper on t'bay the other day for £80 buy it now. might be worth considering it as it's supposed to help.


At least that's what everyone who's fitted them say.

[elbrownos]

My rear brake was great until a few months ago, I've got HH pads and had absolutely no problem locking it up.
I'm inclined to think air is the more likely explanation. Will have another really good go at bleeding it this weekend.
I don't really want to have to start messing around with the master cylinder. Why is it so hard to buy a kit for it???

[bootz76]

Yamaha do the kit but it nearly £70

[Dead Eye]

I've found previously that I've needed to bleed the banjo bolt connections as well... its messy, but an old rag will sort most of it and it may help get rid of any air bubbles lodged there

[red98]

hi elbrownos....what method are you using to expel the air from your breaking system....i think this might be the answer to your problem.........

[elbrownos]

Just flushing through to the bleed nipples. It worked fine after I overhauled the caliper so I don't think my technique is wrong.
The thing that puzzles me is that the braking performance deteriorated without me doing anything. Can air just get into the system by itself?

[red98]

Just flushing through to the bleed nipples. It worked fine after I overhauled the caliper so I don't think my technique is wrong.
The thing that puzzles me is that the braking performance deteriorated without me doing anything. Can air just get into the system by itself?

when you say "flushing through" are you loosening the nipple,pressing pedal and holding,tighten nipple and releasing pedal untill all air is expelled . 

[Deefer666]

Probably the master cylinder needing new plunger and seals.

[elbrownos]

I sorted this, it was air.
I thought it might be a bubble at the top of the master cylinder, so I took the caliper off (leaving the hose attached) and held it above the master cylinder while bleeding. Problem solved!