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TM 5-4320-306-24
4-10. REPLACE/REPAIR PISTON ASSEMBLY (Continued)
2
Inspect piston (3), piston skirt (4), and all grooves (2) for excessive wear (6) and damage. Examine piston for
slight scoring (6), heavy scoring (17), fretting, pitting, cracks (8) (especially on the interior surfaces), damaged
ring grooves or lands, or indications of overheating (9) Slight scoring may be cleaned with crocus cloth. Follow
procedure described under repair.
3
If piston is badly worn or damaged, check cylinder for excessive out-of-round, high spots, or other damage in
accordance with paragraph 4-9.
CAUTION
Pistons, piston rings, and cylinders must always be matched to the same size. Failure to match all three in
size could cause serious damage to the engine.
4
Replace piston (3) if tin plate or ring grooves (2) are excessively worn or damaged, ring lands (1) are damaged;
piston is heavily scored or cracked, or shows signs of excessive overheating.
5
Measure piston diameter along axis A and B. Piston diameter should be 3.9331 to 3.9338 inches (99.901 to
99.919 mm). If piston is out-of-round, replace piston.
6
If cylinder has been replaced, piston must also be replaced Refer to paragraph 4-9 for more detail on cylinder
replacement.
4-74
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