Rebuild brake cyclinder but i'm cheap.

[georgesgiralt]

Hello !
A kit including the piston to renew the master cylinder is around 23 GBP at motobins. Add to this the .95 GBP for the o-ring.
Then there is the ATE rebuild kit at 29 GBP (seals and protection for the 2 calipers).
Not so expensive for peace of mind and good braking, isn't it ?
Somewhere (maybe Moto Bayer) they sell the ATE pistons if yours are rusted beyond reclaim.  
The build quality of the ATE calipers is lees good than the Brembo but once rebuild and with new brake fluid in them they will stop you just the same as the Brembo...
For the Brembo brake caliper, there is a Brembo  kit to renew all "rubber" parts and the two Allen screw holding the two halves which is quite cheap also. So if the pistons are not worn out, it's the way to go. (the two screws are so rusted that once removed you won't ask yourself why they put new ones in the kit...)

[montmil]

Brembo components and parts are also available through these resources

http://www.yoyodyneti.com/

http://shop.bevelheaven.com/index.php

http://www.mgcycle.com/