TM 9-2320-272-24-2
4-31. AIR COMPRESSOR MAINTENANCE (Contd)
Inspect connecting rod bushing (5) for scoring and damage. Replace connecting rod bushing (5) if
12.
scored or damaged.
Inspect connecting rod (4) for bends or twists and inspect connecting rod bores (7) and (6) for wear.
13.
Replace connecting rod (4) if bend exceeds 0.002 in. (0.05 mm) or if twist exceeds 0.004 in.
a.
(0.10 mm).
b.
Replace connecting rod (4) if inner diameter of connecting rod bore (7) exceeds 0.689 in.
(17.50 mm).
C.
Replace connecting rod (4) if inner diameter of connecting rod bore (6) exceeds 1.935 in.
(49.15 mm).
Measure outside diameter of piston pin (2) for wear. Replace if outside diameter is less than 0.687 in.
14.
(17.45 mm).
Inspect piston (1) for scoring, cracks, and damage and measure piston skirt (3) and pin bore (8)
15.
a.
Replace piston (1) if scored, cracked, or damaged.
b.
Replace piston (1) if piston skirt (3) diameter is less than 3.617 in. (91.86 mm) at 70F (21C).
C.
Replace piston (1) if piston bore (8) diameter is more than 0.689 in. (17.50 mm) at 70F (21C).
Install new compression ring (9) in compression ring groove (10) of piston (1). Insert 0.009 in.
16.
(0.23 mm) feeler gauge between compression ring (9) and groove (10). Replace piston (1) if
compression ring (9) can be pressed below piston surface with feeler gauge in place.
Seat new compression ring (12) in unworn portion of cylinder bore (11) and measure ring end gap with
17.
feeler gauge. Gap should be between 0.010-0.020 in. (0.25-0.51 mm). Use different sized ring (12) if
necessary.
NOTE
The maximum crankcase bore is 3.6285 in. (92.16 mm). The
maximum out-of-round specification is 0.0014 in. (0.036 mm).
Inspect cylinder bore (11) for scoring. Burnish cylinder bore (11), as required, to remove scoring.
18.
19.
Using inside micrometer, measure cylinder bore (11) for out-of-roundness. If out-of-round
measurement is not within specifications, hone bore to receive 0.010, 0.020, or 0.030 in. (0.25, 0.51,
or 0.76 mm) oversize piston (1) and ring (9).
20.
Measure inside diameter of crankcase bushing (14). Replace crankcase bushing (14) if measurement
exceeds 1.878 in. (47.70 mm).
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