TM 10-3930-660-34 3-14. PISTONS, PISTON PINS AND RINGS - REPLACE (Cont’d) 2. REMOVE AND DISCARD PISTON RINGS (6, 7 AND 8) AND OIL RING EXPANDER (9). CLEANING NOTE Refer to Cleaning Instructions,  para. 2-10,  for general cleaning information and for appropriate warnings regarding use of solvents and compressed air. CAUTION Do not use bead blast to clean pistons. Bead blasting may damage piston. 1. SOAK PISTONS (3) IN DRY CLEANING SOLVENT P-D-680 TO REMOVE CARBON DEPOSITS. 2. WASH PISTONS IN A STRONG SOLUTION OF LAUNDRY DETERGENT AND HOT WATER,  TO REMOVE CARBON RESIDUE.  USE A STIFF BRISTLE BRUSH. 3. CLEAN RING GROOVES IN PISTON (3) USING SQUARE END OF A BROKEN PISTON RING (10).  USE CARE TO AVOID SCRATCHING RING SEALING SURFACES IN PISTON GROOVES. 4. CLEAN PISTONS AGAIN IN SOLUTION OF LAUNDRY DETERGENT AND HOT WATER. 5. RINSE PISTONS IN CLEAN, FRESH WATER AND DRY USING COMPRESSED AIR. INSPECTION 1. VISUALLY INSPECT RING GROOVES, PISTON TOP, PISTON SKIRT AND PISTON PIN BORE FOR CRACKS OR OTHER DAMAGE AND FOR EXCESSIVE WEAR. 2. CHECK PISTON SKIRT DIAMETER USING AN INSIDE MICROMETER (11) AS SHOWN, AT A POINT APPROXIMATELY 1/2 INCH ABOVE BOTTOM EDGE OF PISTON.  MINIMUM ALLOWABLE SKIRT DIAMETER IS 4.0088 INCH. 3-95 TM 10-3930-660-34