What was found
WHEN THE PILOT PUSHED THE POWER LEVER UP ON THE TAKEOFF ROLL HE HEARD TWO LOUD BANGS COMING FROM THE ENGINE COMPARTMENT. HE ABORTED TAKEOFF AND RETURNED TO THE RAMP. THE PRE-TAKEOFF RUN UP WAS UNEVENTFUL. MECHANIC RAN THE ENGINE AND HEARD THE SAME LOUD BANG. IT WAS DETERMINED THAT THE BLEED AIR VALVE NEEDED TO BE CHANGED. MECHANIC WITH PARTS TO REPAIR THE AIRCRAFT. GAINED ACCESS TO BLEED VALVE. INSTALLED, TORQUED AND SAFETIED SERVICEABLE BLEED VALVE. CLOSED ACCESS. RAN AIRCRAFT, NO CHANGE, COMPRESSOR STILL STALLS. ADJUSTED BLEED VALVE PER P&W PT6 MM 75-30-00 (C) (1). SAFETIED AS REQUIRED. OPERATIONAL CHECK GOOD.