TM 5-3810-300-24 & P2
Check the unloader bore bushings to be sure they are not worn, rusted, or damaged. If these bushings are to be replaced,
they can be removed by running a 1/8" pipe thread tap into the bushing, and inserting a 1/8" pipe threaded rod and pulling
the bushing straight up and out. Do not use an easy-out for removing these bushings. If the inlet valve seats are worn or
damaged, so they cannot be reclaimed by facing, they should be replaced. Cylinder bores which are scored or out of
round by more than 0.001" or tapered more than 0.002" should be rebored or honed oversize. Oversized pistons and
piston rings are available in 0.010", 0.020" and 0.030" oversizes. Cylinder bores must be smooth, straight, and round.
Clearance between the cast iron pistons and cylinder bores should be between 0.002" minimum and 0.004" maximum.
4. Pistons.
Check the pistons for scores, cracks, or enlarged ring grooves; replace the pistons if any of these conditions are found.
Measure each piston with a micrometer in relation to the cylinder bore diameter to be sure the diametral clearance is
between 0.002" minimum and 0.004" maximum.
Check the fit of the wrist pins to the pistons and connecting rod bushings. The wrist pin should be a light press fit in the
piston. If the wrist pin is a loose fit, the piston and pin assembly should be replaced. Check the fit of the wrist pin in the
connecting rod bushing by rocking the piston. This clearance should not exceed .0007". Replace the wrist pin bushings if
excessive clearance is found. Wrist pin bushings should be reamed to between .5314" and .5317" after being pressed into
the connecting rods. Replace the used wrist pin lock wires
Check the fit if the piston rings in the piston ring grooves.
Check the ring gap with-the rings installed in the cylinder
bores.
5. Crankshaft.
Check the crankshaft threads, keyways, tapered ends and all machined and ground surfaces for wear, scores, or damage.
Standard crankshaft journals are 1.1250"1.1242" in diameter. If the crankshaft journals are excessively scored or worn or
out of round the crankshaft must be replaced. Connecting rod bearing inserts are available in 0.010", 0.020" and 0.030"
undersizes for compressors with reground crankshafts. Main bearing journals must be maintained so the ball bearings
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