(5) Fit the pistons on the cylinder liners as fol-
Move the piston to the bottom of its travel
and place a cloth on the top of the piston to
collect cuttings. After reaming is completed,
If any bind between piston and liner is detect-
turn the crankshaft until the piston is at the
ed, remove the piston and inspect piston and
top of its stroke and carefully remove the
liner for burrs. Remove burrs with a fine
cloth with cuttings.
(a) Refer to table 1-1 and measure the piston
(5) Remove the piston and connecting rod assem-
skirt diameter and cylinder liner bore. Take these
as shown in figure 3-108.
measurements with the piston and liner at normal
room temperature (72°F).
(1) Disassemble the piston and connecting rod as-
(b) Refer to table 1-1 and check the piston to
sembly in numerical sequence as shown in figure
liner clearance. Check this in four places, 90° apart
while holding the piston upside down in the cylinder
(2) Position the connecting rod and piston assem-
liner as shown in figure 3-111.
bly in a bench vise with soft jaws and remove the pis-
(c) The spring scale attached to the appropriate
ton rings with a ring expander as shown in figure
feeler gage is used to measure the force of pounds re-
quired to withdraw the feeler gage from between the
(3) Punch a hole through the center of piston pin
piston and the liner. The clearance will be 0.001 inch
retainer (9, fig. 3-109) with a narrow chisel or punch
greater than the thickness of the feeler gage used
to pry the retainer from the piston (15).
when it is withdrawn at a pull of six pounds. The feeler
(4) Remove the piston (15) from the rod (12). Use a
gage must be flat and free of nicks and bends.
brass rod to remove the remaining retainer (9) from
(6) Fit the piston rings as follows:
(5) Do not remove piston or rod bushings (11 and
Use new piston rings whenever a piston is re-
14) or the rod spray nozzle (13), unless inspection indi-
moved for inspection or replacement.
cates replacement is required.
(a) Refer to table 1-1 and measure the gap be-
tween the ends of the piston rings before installing
(1) Clean all parts with cleaning solvent P-D-680
rings on piston.
dry thoroughly with compressed air.
(2) Clean carbon from the top of the piston using a
(3) Using a suitable tool, clean the carbon from
the piston ring grooves.
(4) Use a suitable size drill and clean the carbon
from the eight oil control holes in the bottom of the
piston oil ring grooves.
e. Inspection and Repair.
(1) Inspect the pistons for scoring, overheating,
cracks or damaged ring grooves. A piston with light
score marks can be cleaned up and reused.
(2) Refer to table 1-1 and inspect and measure the
piston pins and pin bushings. -
(3) Replace the piston bushings as follows:
(a) Place the piston in a holding fixture and
drive the bushings from the piston.
(b) Place the fixture spacer in counterbore of
holding fixture, small end up. Place the piston on the
holding fixture so that the spacer protrudes into the
pin bushing bore.
(c) Locate the joint in the bushing toward the
of the piston, insert the installer handle and
drive the bushing in until it bottoms on the spacer.
(d) Install the opposite pin bushing in a similar
(4) Refer to table 1-1 and ream the piston pin
bushings to the value listed.