Rear master cylinders... Do they go wrong?

[mr self destruct]

Looks like the old back brake problem has reared it's ugly head again.
Got to work today to find the back wheel really stiff and red hot. The familiar smell of cooked pads hit me too.
Thing is, the old caliper seized, so I did the Thou mod with a caliper I had rebuilt just to be on the safe side (nothing against the lad I bought it off, it just pays to be sure), now that seems seized too.
I'm wondering if it's a master cylinder problem instead? After all, I didn't really check the old 600 caliper over after taking it off, I was just pissed off with it so junked it.


Has anyone got experience with master cylinder problems?

[Fazerider]

Not impossible, but unusual.
Are you sure the pivot for the pedal is clean and lubricated? If neglected that can get so stiff the return spring isn't sufficient to pull the lever back up.

[mr self destruct]

I'll check that out. It's possible as I do ride it in all weathers and TBH the whole bike needs a bit of care.

[darrsi]

Not impossible, but unusual.
Are you sure the pivot for the pedal is clean and lubricated? If neglected that can get so stiff the return spring isn't sufficient to pull the lever back up.

 
I've always kept my brake and gear levers clean at the joints ever since my rear braking went a bit spongy.
Crud can unwittingly build up over time and really affect braking.
Quick blast of brake cleaner is one way and an oil lube, or even just a spray of WD40 is good enough every month or so to keep rear braking in traffic really sharp.

[unfazed]

Rear master cylinder rarely gives trouble, in fact the same unit is used in the both the FZS 600 and 1000 (part number 4BP-2583v-01)
The biggest issue is the lever can seize on the footrest. WD40 will sort it temporarily, but best option is to remove it and grease it if it does happen..

[BBROWN1664]

Quick way to check. Crack open the bleed nipple on the caliper and see if any fluid comes out when you press down on the pedal.

[Jamieg285]

No direct experience with an MC failure, but I'd say it was highly unlikely an MC will stick.  It's more likely to leak, leading to less power to the brake.  More likely is it being held by the pedal mechanism, or perhaps you've just been unlucky with the calipers sticking.

Are you sure you've not been accidently resting on the pedal when riding? 

How long has the new caliper been on, and how often have you given it a clean (general clean, when it's on the bike - not a service/clean).

[mr self destruct]

No direct experience with an MC failure, but I'd say it was highly unlikely an MC will stick.  It's more likely to leak, leading to less power to the brake.  More likely is it being held by the pedal mechanism, or perhaps you've just been unlucky with the calipers sticking.

Are you sure you've not been accidently resting on the pedal when riding? 

How long has the new caliper been on, and how often have you given it a clean (general clean, when it's on the bike - not a service/clean).

Knowing my luck the caliper could be shagged!  It's been on about two months I reckon and the bike's been cleaned at least once a week, but i do 250 miles a week in all weathers so could get gunked up.


I make a point of riding with the balls of my feet on the pegs, so resting my foot on the pedal isn't the problem.


I got home last night (after riding from work without touching it as it had freed off during my shift) and gave the pedal spindle a soaking with carb & brake cleaner, then WD40. Didn't touch it on the way in to work today but I'll see how it is on the way home, as at least I can get AA'd if it goes a bollock again.

[darrsi]

On the centre stand the rear wheel (and front) should spin freely with little effort, if the caliper is seizing up then it should be quite obvious due to heavy friction, plus you may notice one brake pad worn much more than the other one.
You'll have even more fun and games in the future when you need to replace the rear disc, the bolts should be firmly welded to the wheel hub by now. 

[Jules-C]

Check the brake fluid reservoir isn't filled to the brim if it's filled too high you can end up with pressure in the system

[mr self destruct]

Tried it out on the way home again after giving it a good soaking and greasing, and it seems ok now so must have been the pedal.
Thanks for your help guys, I'll keep on top of the cleaning a bit better!

[daviee]

strip it off clean it and grease it properly that routine maintenance