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TM 5-4320-305-24
4-10. REPLACE/REPAIR PISTON ASSEMBLY (Continued)
PISTON RING
NORMAL SIDE
CLEARANCE
inches
(millimeters)
SIDE CLEARANCE
WEAR LIMIT
inches
(millimeters)
First or trapezoidal
0.0031 to 0.0047
0.0197
ring
(0.079 to 0.119)
(0.5)
Second or taper
0.0039 to 0.0052
0.0118
ring
(0.10 to 0.132)
(0.3)
Third or oil control
0.0016 to 0.0028
0.0059
ring
(0.041 to 0.071)
(0.15)
b.
If piston ring (1) side clearance for any piston ring is less than normal lower limit value given in chart, replace
piston ring and measure side clearance again. If condition still exists, replace piston (4). If side clearance for any piston
ring exceeds wear limit in chart, replace piston. Also replace cylinder, if necessary.
REPAIR:
1
Remove slight scoring or fretting on piston with crocus cloth. Reclean and repeat procedure if necessary.
2
If gap on new compression ring is insufficient, it may be increased by filing or stoning the ends of the ring. File or
stone both ends of ring so cutting action is from outer surface to inner surface. This will prevent any chipping or
peeling of chrome plate on ring. The ends of the ring must remain square with chamfer on outer edge.
3
If cylinder is worn or damaged, repair or replace in accordance with paragraph 4-9.
4-79
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