TM 5-4310-379-14
5-20.
Pistons and Connecting Rods (Cont).
b.
Repair. (figure 5-23)
NOTE
Do not reuse piston rings or retaining rings. It may be necessary to punch a hole in retainer to remove.
(1)
Remove two retainers (1) and slide piston pin (2) out of piston (3) and connecting rod (4).
(2)
Using piston and connecting rod bushing remover, remove bushing (5) from piston (3).
(3)
Using piston and connecting rod bushing remover, remove bushing (6) from connecting rod (4).
(4)
Using piston ring assembly tool, remove four compression rings (7), two expanders (8), two oil controlrings
upper half (9), and two oil control rings lower half (10) and discard rings.
WARNING
Dry cleaning solvent PD-680 used to clean parts is potentially dangerous to personnel and property. Avoid
repeated and prolonged skin contact. Do not use near open flame or excessive heat. Flash point of
solvent is 100-138°F (38-60C).
(5)
Clean all items with dry cleaning solvent, and dry thoroughly.
(6)
Inspect piston (3) for score marks, cracks, ring groove lands, or indications of overheating. Replace piston if
severely scored or overheated.
(7)
Inspect piston for cracks, using the magnetic particle inspection (refer to para. 5-19a). If piston is cracked,
replace piston.
NOTE
Taper and out-of-round, measured from a point approximately 1.88 in. (4.77 cm) from top of piston to
bottom of piston, must not exceed .0005 in. (.0012 cm).
(8)
The piston skirt diameter must be measured lengthwise and crosswise of the piston pin bore.
NOTE
Inside diameter of bushing in piston is 1.5025-1.5030 in. (3.8163-38176 cm) and outside diameter of
piston pin is 1.4996-1.5000 in. (3.8089-3.8100 cm). Piston pin-to-bushing clearance is .0025-.0034 in.
(.0063-.0086 cm). A maximum clearance of .010 in. (.025 cm) is allowable with worn parts.
(9)
Check piston pin-to-bushing clearance, if clearance is larger than allowable to tolerance, replace piston pin.
5-74
