Abstract: A master cylinder assembly for a hydraulic actuation system for a handlebar-steered vehicle including a fluid cavity having an adjustable length. The master cylinder assembly generally includes a housing, a piston assembly, an actuator and an adjuster. The housing is mountable to a frame member and includes a chamber having a fluid cavity with first and second regions. The first region is in fluid communication with the hydraulic actuation system. The piston assembly includes a piston slidably disposed within the fluid cavity. The actuator is operatively connected to the housing and operatively connected to the piston to slidably displace the piston between an open fluid circuit position permitting fluid flow between the first and second regions and a closed fluid circuit position blocking fluid flow between the first and second regions. The adjuster is operatively connected to the housing to adjust a length of the fluid cavity.