Patent ID: 7757488

Claim:
A master cylinder assembly for a hydraulic actuation system for a handlebar-steered vehicle, the master cylinder assembly comprising: a housing mountable to a frame member of the handlebar-steered vehicle and having a chamber including a fluid cavity and an air cavity, the fluid cavity having first and second regions, the first region in fluid communication with the hydraulic actuation system; a piston assembly including a piston slidably disposed within the fluid cavity; an actuator operatively connected to the housing and operatively connected to the piston to slidably displace the piston between an open fluid circuit position and a closed fluid circuit position; a first seal disposed on one of the piston and a wall of the fluid cavity; and a sealingly-separating member separating the air cavity from the fluid cavity, at least a portion of the sealing-separating member attached to and slidably displaced with the piston, the first seal configured to be in sealing engagement between the fluid cavity wall and the piston with the piston in the closed fluid circuit position to block fluid flow between the first and second fluid cavity regions, the first seal configured to be in non-sealing disengagement between the fluid cavity wall and the piston with the piston in the open fluid circuit position to permit fluid flow between the first and second fluid cavity regions.