What was found
DURING TAXI OUT FOR REPOSITIONING FLIGHT, PILOT FELT A PULSE FROM THE LEFT RUDDER PEDAL AND THEN A UNCONTROLLABLE TURN TO THE RIGHT. PILOT USED MAXIMUM BRAKING AND THROTTLES TO IDLE TO STOP AIRCRAFT. MAINTENANCE REBUILT, SERVICED, AND BLED THE LEFT BRAKE MASTER CYLINDER, NO FURTHER DEFECTS REPORTED.