TM10-3930-660-20 W -  Weekly Q - Quarterly S -  semiannually A  -  Annually Item To Be Inspected Procedure: Check for and repair, fill or adjust as necessary ENGINE ASSEMBLY Check the engine drive belt for wear. Firmly press the belt  midway  between  its  longest  span.  Maximum  deflection should be 3/8 to 1/2 inch. If drive belt is worn or stretched, refer to para.   7-9 for drive belt replacement. Drive belt tension is not adjustable. ENGINE MOUNTS Check engine mounts for cracks, deterioration and damage. BATTERIES Do not smoke or allow any flame or spark in the vicinity while checking or filling the batteries. The batteries generate hydrogen gas, a highly explosive  gas.  Severe  personal  injury  could  result. Test batteries to determine cell condition. Replace  or recharge. Refer to TM9-6140-200-14. SERVICE BRAKES Check brake pads for wear. Pads should not be allowed to wear below 1/8 inch in thickness. Refer to para. 12-6 for wear pad replacement procedures. Check brake rotors for grooves, discoloration, cracks, and  warpage. PROPELLER SHAFTS Check all propeller shaft universal joints for excessive vibration or noise. Refer to para. 10-3 for replacement procedures. 2-7