TM 5-4930-218-14
(1) Clean all parts with dry cleaning solvent (fed.
to 25 foot-pounds maximum.
(4) Install the intake and exhaust valves (para 7-
spec. P-D-680) and dry thoroughly.
(2) Inspect the cylinder for broken cooling fins
(5) Install the exhaust manifolds (para 7-4) and
and cracks; replace a damaged cylinder.
head unloaders (para 7-3).
(3) Inspect the cylinder bore for wear, scoring,
(6) Install the handhole plate and new gasket
pitting, or other damage. Inspect the bores for out-of-
roundness by placing an inside micrometer in the top
(7) Install compressor flywheel (para 7-2).
of the cylinder bore and taking two measurements, 90
(8) Install the oil drain plug (6, fig. 7-2).
degrees apart. Repeat the procedure halfway down
the bore, The difference between the two
measurements is the amount the bore is out of round.
Replace or resize the cylinder if out-of-roundness is
a. Removal and Disassembly.
over 0.002 inch.
(1) Remove oil drain plug (6, fig. 7-2) and drain
(4) Measure the clearance of the piston pin in the
oil.
piston pin bushing, Desired clearance is 0.0002 and
(2) Remove compressor flywheel (para 7-2).
0.0009 inch. Maximum allowable piston pin clearance
(3) Remove handhole plate and gasket (para 7-7).
is 0.001 inch.
(4) Remove the centrifugal unloader (para 7-6).
(5) Inspect the connecting rods for visible
(5) Remove the connecting rod caps (2, fig. 7-3).
damage or misalinement. Realine slightly twisted
The connecting rods are accessible through the hand-
rods or replace if they are badly damaged,
hole plate in the bottom of the crankcase (38, fig. 7-2).
(6) Place the piston rings in the cylinder bore in
The caps are matched with the connecting rod, Tag
which they will be used and measure the ring gap
the cap to identify it with appropriate rod to insure
with a feeler gage. Position the piston ring square
correct reassembly.
with the cylinder bore about one half inch from the
(6) Remove the crankshaft from the crankcase as
top. The correct gap for the small compression and oil
illustrated in figure 7-3. The bearing cones and
rings is 0.0012 0.005 inch.
rollers (12) are pressed on the shaft and will come out
(7) If the ring gap is less than the specified
with the crankshaft.
width, you should file across the butt ends of the ring
(7) Place the crankshaft (13, fig. 7-3) in a suitable
to increase the gap to the required tolerance. If the
press and carefully remove the two tapered bearing
ring gap is greater than 0.023 inch for any ring,
cones and rollers (12) from the crankshaft.
replace the entire set of rings.
(8) Using a blunt instrument, drive the bearing
(8) Measure the ring groove in the pistons for
cup (11) and oil seal (37, fig, 7-2) out of the flywheel
wear and side clearance, using a feeler gage between
side of the crankcase, Discard oil seal. Remove the
the ring and groove side wall. The desired ring groove
bearing cup (11, fig, 7-3) from the governor housing
clearance is 0.0010 to 0.0025 inch for the low-pressure
(35, fig. 7-2),
rings and 0.0010 to 0.0045 inch for the high-pressure
b. Cleaning, Inspection and Repair.
rings.
NOTE
c. Reassembly and Installation.
Refer to table 7-1 for compressor repair and
replacement standards.
NOTE
(1) Clean all parts except the bearings with dry
Refer to table 7-1 for compressor repair and
cleaning solvent (fed. spec. P-D-680) and dry
replacement standards.
(1) Refer to figure 7-3 and reassemble the pistons
thoroughly.
(2) Place the bearings in a wire basket, dip in dry
and connecting rods in the reverse order of disassem-
cleaning solvent and dry with low pressure com-
bly. Lubricate each piston and connecting rod assem-
bly with a light coat of engine oil.
pressed air. Do not spin the rollers. Dip in light oil.
(2) Install the assembled pistons and connecting
(3) Inspect the bearings for free and even
rotation. Replace if defective,
rods into the cylinder block. Install the cylinder block
(4) Inspect the crankshaft for cracks, scores, and
assembly (64, fig. 7-1) and gasket (65) on the crank-
distortion, You should measure the crankshaft
case, Tighten the cylinder block screws to 45 foot-
bearing journals for wear, using an outside
pounds torque.
(3) Attach connecting rods to crankshaft and
micrometer. If the shaft measures more than 0.0005
secure with connecting rod and cap (2, fig. 7-3) and
out-of-round, metallize the crankshaft and turn down
connecting rod bolt (1). Make sure the caps are fitted
to correct size. The correct size for main bearing jour-
to the rods from which they were removed. The con-
nals is 1.376 to 1.377 inches. The correct size for con-
netting rod cap and connecting rod are matched
necting rod journals is 1.623 to 1.625 inches.
parts and should not be interchanged. Tighten bolts
(5) Inspect the bearing cups for scores, burrs,
