'06 ZX636 master cylinder problems?

[BADGRL]

Hey guys,

has anyone ever had any probs with their ninjas in relation to the front master cylinder? I originally bought the bike with no front brakes, bled them and they're sweet but have since gone soft again (over 1 mnth/500kms).

I suspect the very top bleeder valve is ever so slightly letting air into the master cylinder and down into the lines. With the bleeder valve nipped up tight I can still suck air/fluid out but can't blow it back in... thought it may have been a 1 way valve but nah the lines are still getting air in them.

Would replacing just the bleeder valve help? When it's nipped up what seals it off? Is it the valve itself or something inside the m/c?
Any advice would be much appreciated :)

[SVboy]

I cant answer your questions-but is this karma for swapping your drz!!!

[Wiki Drifter]

Brakes became soft on mine, bled them, replaced the fluids etc, but they went soft again after a few days.
In the end I had to replace the entire master cylinder. :wacko:

[BADGRL]

I cant answer your questions-but is this karma for swapping your drz!!!
Haha probably, I miss the drz like CRAZY!! Will definately buy another one eventually ;)

[BADGRL]

Brakes became soft on mine, bled them, replaced the fluids etc, but they went soft again after a few days.
In the end I had to replace the entire master cylinder. :wacko:


Damn that's the wrong answer! lol. Best I start looking for a second hand m/c or rebuild kit :S

[imdying]

If air can get in, fluid will get out. If it's not leaking it should be fine.

[BADGRL]

If air can get in, fluid will get out. If it's not leaking it should be fine.
But that's what has me stumped! It's dry as, not leaking in the slightest... definately air getting down the lines and this is the only suspect valve :S Could it be 'cos other than the reservoir this valve is the 2nd highest point of the brake lines so gravity is stopping fluid from coming up and also sucking air down?? lol

Maybe I just source a second hand m/c and fingers crossed :D

[FJRider]

But that's what has me stumped! It's dry as, not leaking in the slightest... definately air getting down the lines and this is the only suspect valve :S Could it be 'cos other than the reservoir this valve is the 2nd highest point of the brake lines so gravity is stopping fluid from coming up and also sucking air down?? lol

Maybe I just source a second hand m/c and fingers crossed :D

Maybe it is the fluid quality that is the issue. When it was last bled ... was it just topped, up or changed. Change the fluid and check/replace seals.

[FJRider]

If air can get in, fluid will get out. If it's not leaking it should be fine.

Not entirely correct ...

http://soarer.ace.net.au/brake_fluid.html

[BADGRL]

Maybe it is the fluid quality that is the issue. When it was last bled ... was it just topped, up or changed. Change the fluid and check/replace seals.

Yeah when I got the bike I was hoping that's all I'd have to do ;) I've completely flushed out the lines and reservoir with high quality fluid and over the month it's nearly back to how they were.

Ooow you say seals, is there one in the m/c itself? I went into Kawasaki and they obviously hadn't come accross this before :S

[FJRider]

Yeah when I got the bike I was hoping that's all I'd have to do ;) I've completely flushed out the lines and reservoir with high quality fluid and over the month it's nearly back to how they were.

Ooow you say seals, is there one in the m/c itself? I went into Kawasaki and they obviously hadn't come accross this before :S

Refer to your workshop manual of your model. Seals will be cheaper than a new unit/system ...

High quality fluid (or expensive/new) ... ???

http://en.wikipedia.org/wiki/Brake_fluid

[BADGRL]

yup some new fluid, I swear by the Castrol Super4 I think it is - goes up to dot5.1 :) .... *hunts for the manual

[jellywrestler]

if 'air' can get in fluid will be apparent as rememeber it's under a lot of pressure in operation. As for new seals rarely do i fit new seals the majority of the time it's a matter of a careful clean and reinstall. next thing is to check your method of bleeding there's a fine art to some systems to get it right

[ducatilover]

I'm not sure if 5.1 will work in your M/C (synthetics can be fucking horrid to brakes not made for 'em)

I would re-kit your M/C assuming the bore in it is okay.

[Wheeliemonsta]

The problem lies in the bore diameter on the master cylinder which is a 5/8ths (15mm) inch from memory...

If you want to retain the original cylinder the only way you will get a good consistant lever is to have them pressure bleed using a good quality Dot 4 or 5 fluid (as they are ex factory), during this time the rest of the system can be inspected for any further faults such as a bypassing cylinder set etc etc...

The permanent fix is to either have the cylinder line bored to take a 3/4 inch (19mm) cylinder set or replace it with an appropriate Brembo unit which retail for around for $500 dependent on how flash a model you want...

Cheers

:rockon:

[FJRider]

yup some new fluid, I swear by the Castrol Super4 I think it is - goes up to dot5.1 :) .... *hunts for the manual

Don't swear as loud then .... if it's that fluid that has let you down. AGAIN.

[FJRider]

I'm not sure if 5.1 will work in your M/C (synthetics can be fucking horrid to brakes not made for 'em)

Actually ... from what I have read on brake fluids ... Dot 3, Dot 4. and Dot 5.1 are Glycol based fluids.
Dot 5 is Silicone based fluids. (the synthetic one) and should not be used in systems that previously used Glycol based fluids ... (without a major clean and replacement of NEW seals)

[ducatilover]

Actually ... from what I have read on brake fluids ... Dot 3, Dot 4. and Dot 5.1 are Glycol based fluids.
Dot 5 is Silicone based fluids. (the synthetic one) and should not be used in systems that previously used Glycol based fluids ... (without a major clean and replacement of NEW seals)
All the 5.1 I've used is synth, with mixed results on master cyls, I now don't use synth unless the factory does, even though it's claimed to be compatible
The 5.0 is much worse though, haven't seen it around for a while, 5.1 is always claimed to be backwards compatible, but it's not always the case.

[FJRider]

All the 5.1 I've used is synth, with mixed results on master cyls, I now don't use synth unless the factory does, even though it's claimed to be compatible
The 5.0 is much worse though, haven't seen it around for a while, 5.1 is always claimed to be backwards compatible, but it's not always the case.

I did a quick Google on synthetic brake fluid. This was just one result ...

http://www.synlube.com/brake.htm

It would appear that the DOT (meaning US Department Of Transportation) status number does not relate directly to it being synthetic ... or not. Thus it should not be assumed ... as such ... that it is.
We should read the labels more closely perhaps.

I learn new things each day ...

[ducatilover]

I did a quick Google on synthetic brake fluid. This was just one result ...

http://www.synlube.com/brake.htm

It would appear that the DOT (meaning US Department Of Transportation) status number does not relate directly to it being synthetic ... or not. Thus it should not be assumed ... as such ... that it is.
We should read the labels more closely perhaps.

I learn new things each day ...
As I said, all the 5.1s I've used have been synth, but I've never look for a mineral one.
In the rally car we can't run synth, the old Willwood masters really don't like it.
I ran synth 5.1 in my Spada for the 130,000km I owned it with no issues :yes: but, yes read the labels as not all of it can be mixed and some synth will make a mess of brake parts designed for minerals.

[FJRider]

but, yes read the labels as not all of it can be mixed and some synth will make a mess of brake parts designed for minerals.

Perhaps part of the OP's original issue. ??????????

[Owl]

I thought all brake fluids were "synthetic" and that word is just a marketing tool?

[CHOPPA]

Have a chat to ray clee apparently it it's something to do with the top bled.same prob with Suzuki

[FJRider]

As I said, all the 5.1s I've used have been synth, but I've never look for a mineral one.
In the rally car we can't run synth, the old Willwood masters really don't like it.
I ran synth 5.1 in my Spada for the 130,000km I owned it with no issues :yes: but, yes read the labels as not all of it can be mixed and some synth will make a mess of brake parts designed for minerals.

I Googled "Castrol Super 4" .. here is one result ...

This is a fully synthetic brake fluid that exceeds the boiling point specifications of most DOT 5.1 fluids and is no more costly. For road use this is fine.

This can be hard to locate, also very important to note that it is Super as Castrol do also sell a normal response DOT 4.

Hard track use with extended high temperatures over 30 minute sessions needs some further consideration; regular change of less expensive fluid or more expensive race fluid changed less? There is no right answer.

The function of brake fluid is to provide an incompressible medium to transmit the driver’s foot pressure to clamp the friction material against the discs. When fresh, all brake fluids are virtually incompressible, but overheated brake fluid will boil in the calliper producing gas bubbles which are compressible leading to a “soft” brake pedal with long travel.

[DMNTD]

The problem lies in the bore diameter on the master cylinder which is a 5/8ths (15mm) inch from memory...

If you want to retain the original cylinder the only way you will get a good consistant lever is to have them pressure bleed using a good quality Dot 4 or 5 fluid (as they are ex factory), during this time the rest of the system can be inspected for any further faults such as a bypassing cylinder set etc etc...

The permanent fix is to either have the cylinder line bored to take a 3/4 inch (19mm) cylinder set or replace it with an appropriate Brembo unit which retail for around for $500 dependent on how flash a model you want...

Cheers

:rockon:

But what would you know, right? :shifty:

[pete376403]

The problem lies in the bore diameter on the master cylinder which is a 5/8ths (15mm) inch from memory...

If you want to retain the original cylinder the only way you will get a good consistant lever is to have them pressure bleed using a good quality Dot 4 or 5 fluid (as they are ex factory), during this time the rest of the system can be inspected for any further faults such as a bypassing cylinder set etc etc...

The permanent fix is to either have the cylinder line bored to take a 3/4 inch (19mm) cylinder set or replace it with an appropriate Brembo unit which retail for around for $500 dependent on how flash a model you want...

Cheers

:rockon:

Really? If this is true then every single 636 with that diameter master cylinder is going to have the same problem. Also, going to a larger master cylinder changes the ratio between master/slave cylinder diameters, which in this case will reduce master cylinder travel (because the amount of fluid per stroke is increased) but will reduce the pressure available at the slave cylinders = weaker brakes.
There's nothing magic about hydraulics, it's effectvely the same as gearing - the ratio between effort applied at the master cylinder to pressure developed at the slave cylinder.

It is however a bit scary the number of threads lately about brakes where some pretty oddball theories have been posted

[BADGRL]

Right that's it I'll drain and strip the m/c tomorrow... will take some pics :) My last 636 needed to have the brakes flushed once a year as they got spongy but no where near as bad as this! My mate's zx10r feels flippen horrible too but I wouldn't dare tell him lol :S

[BADGRL]

sooo I've stripped the m/c and all the seals are in good nick, the only thing I can come up with is the bleeder valve(pic2) isn't seating properly so have ordered a new one but can't pick up 'til 7th damn xmas holidays lol. Will clean it all up and reassemble, see how it goes.

[Wheeliemonsta]

But what would you know, right? :shifty:

:laugh: :laugh: :laugh: True that brother :laugh: :laugh: :laugh:

:girlfight:

Bout time we got some :drinknsin aye what...

Cheers

:rockon:

[Wheeliemonsta]

Really? If this is true then every single 636 with that diameter master cylinder is going to have the same problem. Also, going to a larger master cylinder changes the ratio between master/slave cylinder diameters, which in this case will reduce master cylinder travel (because the amount of fluid per stroke is increased) but will reduce the pressure available at the slave cylinders = weaker brakes.
There's nothing magic about hydraulics, it's effectvely the same as gearing - the ratio between effort applied at the master cylinder to pressure developed at the slave cylinder.

It is however a bit scary the number of threads lately about brakes where some pretty oddball theories have been posted

You raise an intersting point Pete & to be totally honest I completely neglected to mention that it occurs on a bike by bike basis - some you have absolutely no issue with throughout there life others like my own ZX12-R & a friends D6F 636 have been problematic for what seemed like forever (with regard to my own bike - lets please not confuse the already well thrashed "6 pot" pain in the a** to bleed issue with the above)

My post was simply was to advise what I (& pehaps the odd F1 Super bike & F2 I have been involved with) have found to be a permanent fix

Have a search on Google for the explanation of "Centipoise" & think of my suggested fix as applying a "Big Hammer" soloution to the issue

Cheers

[pete376403]

OK I had a (quick) look at centipoise wrt brake fluids and if i'm reading this correctly it is basically a measure of viscosity.

I could see where a thicker (higher viscosity) fluid could make it more difficult to bleed unless using a pressure bleeding pump, but dont see where the diameter of the master cylinder has a bearing, unless the higher volume of fluid displaced per stroke assists.

However, I have only theory, but you have practical experience in the matter.

Did you notice any trade-off in braking performance with the larger master cylinder?

[Wheeliemonsta]

OK I had a (quick) look at centipoise wrt brake fluids and if i'm reading this correctly it is basically a measure of viscosity.

I could see where a thicker (higher viscosity) fluid could make it more difficult to bleed unless using a pressure bleeding pump, but dont see where the diameter of the master cylinder has a bearing, unless the higher volume of fluid displaced per stroke assists.

However, I have only theory, but you have practical experience in the matter.

Did you notice any trade-off in braking performance with the larger master cylinder?

No trade off at all Pete - just a massive improvement in consistancy of performance...

Cheers

[imdying]

Just stick it together and have Mickey ride it down to work tomorrow morning. I'll have a bleeder somewhere, but if it' not leaking then it'll be fine.

Wheeliemonsta makes a interesting point... this is all factory 636 gear from the same year, yes?

[BADGRL]

yup all looks factory to me, all the seals look really good. The whole bike's in exceptional condition it's only done 17clicks, 1 owner with full service history. I cleaned the m/c and put it back together, bled all the lines again over n over and it feels fine BUT I know in a month or so it'll be back to nothing. Nah it's definately not leaking anywhere you may be right maybe it needs a pressure bleed :S Haha Mickey can't ride atm :D

[FJRider]

If the wheel spins freely off the ground ... and you don't ride with one or two fingers covering the brake. it should be ok.

[BADGRL]

If the wheel spins freely off the ground ... and you don't ride with one or two fingers covering the brake. it should be ok.

Haha I like your thinking ;)