What was found
APU BLEED AIR CAUSING VIBRATION - NOISE DURING ENGINE STARTS. LOCKED APU BLEED VALVE CLOSED. REMOVED LT ISOLATION VALVE, LOOKED INSIDE DUCT, NO DEBRIS FOUND. RE-INSTALLED VALVE NOTICED WITH APU BLEED ON THERE IS A SMALL CONSTANT VIBRATION FELT IN THE APU BLEED DUCT. RAN LT ENG AT STARTER CUTOUT DUCT IN LT WHEEL WELL MOVES FORE & AFT. IT APPEARS CLAMP NOT SECURING DUCT TIGHTLY, ITEM 65 NON-STK BACC10CC112C. REPLACED CLAMP AND SECURED DUCT. REPLACED APU SHUTOFF VALVE. OPS CHECK GOOD, NO UNUSUAL VIBRATIONS OR NOISES NOTED.