What was found
WHILE ADVANCING THROTTLES FOR INITIAL TAXI AT APPROXIMATELY 40% N1, A MOMENTARY FIRE BELL AND FIRE WARNING MASTER WARNING. ALL INDICATIONS EXTINGUISHED IMMEDIATELY ON THROTTLE REDUCTION AND WERE NO OTHER ENGINE INSTRUMENT INDICATIONS SUPPORTING A FIRE. TROUBLESHOT THE NR 1 ENGINE IAW FIM FAULT TREE, OPENED COWLING AND CHECKED FOR LOOSE FIRE LOOPS OR CRACKED DUCTS. NO DUCT CRACKED, FOUND 2 LOOSE CONNECTIONS ON THE FIRE LOOP. TIGHTEND IAW AMM 26-11-01-4, REV. REPLACED AFOLTS CARD NUMBER 1 IAW AMM: 26-10-01-4. FIRE WARNING TEST WAS SATISFACTORY. PERFORMED HIGH POWER RUN-UP TO 51% N1 AND 76% N3 WENT MULTIPLE TIMES FROM IDLE TO ABOVE N1 40% AND N1 50% ONE TIME, KEPT STABLE FOR 3 MINUTES AT 47% N1 NO FAULTS OCCURED. AIRCRAFT OK FOR SERVICE.