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TM 5-4320-306-24
4-10. REPLACE/REPAIR PISTON ASSEMBLY (Continued)
pin with micrometer (3) at several points along the length of the pin. The diameter should be 1.3777 to 1.3780
inches (34.994 to 35.0 mm). The diameter should not be greater than 1.3780 inches (35.0 mm) under normal
conditions. However, if it is, replace piston pin and recheck piston bore measurements. Replace piston if
necessary. If piston pin is worn and any diameter measurements are less than 1.3777 inches (34.994 mm),
replace piston pin.
CAUTION
Piston and cylinder damage may result if pistons are not returned to their original cylinders. Observe
matchmarks so that mixups do not occur.
14
Insert each piston (1) in its respective cylinder (2) or replacement, and measure the piston skirt-to-cylinder
clearance with feeler gage (3). If clearance is not within 0.0032 to 0.0166 inch (0.081 to 0.421 mm), inspect
pistons and replace if necessary.
NOTE
Each piston is fitted with three rings: two compression rings and a double-chamfered oil control ring. The
top compression or trapezoidal ring can be identified by the bright chrome plating. The second
compression or taper ring can be identified by its cast iron construction. A double-chamfered oil control
ring is used in the oil ring groove. All new piston rings must be installed whenever a piston is removed or
replaced, or when a new cylinder is installed.
4-77
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