What was found
(CAN) DURING FIRST START OF THE ENGINE, FOLLOWING A TURBINE CHANGE, MAIN ROTOR BLADES INITIALLY STARTED TURNING BUT THEN STOPPED BEFORE ENGINE ACCELERATED TO IDLE SPEED. THE START WAS ABORTED.AME ATTEMPTED TO TURN THE MAIN ROTOR BLADES BACKWARDS BUT WAS UNABLE TO DO SO. THE PT (N2) TURBINE WAS SEIZED. THE A/C WAS BROUGHT INTO THE HANGAR. AFTER APPROXIMATELY 45 MINUTES A LOUD BANG WAS HEARD AND THE N2 TURBINE BROKE FREE. THE TURBINE WAS REMOVED AND RETURNED TO STANDARD AERO. ENGINEERING REPORT WAS REQUESTED.