piston pin. The fit of the connecting rod on
the crankshaft is governed by shims between
the connecting rod and the rod cap. Refer to
Note. It may be necessary to tap lightly
T M 5-2805-203-14, for data applicable to
on the sides of the rod cap with a soft
metal hammer to loosen the cap.
(8) Loosen the connecting rod (13) from
4-31. Piston and Connecting Rod Assembly
the crankshaft (15); then push the
piston and connecting rod upward
a. Removal and Disassembly.
and out through the top of the cylin-
der bore as a unit.
(9) Remove the two shoulder bolts (28)
from the connecting rod.
Note. Before removing the piston and
(10) Use a piston ring expander and re-
connecting rod assembly, remove any car-
move the compression ring (8), two
bon deposits and/or wear ridge from the
compression and scraper rings (9),
upper end of the cylinder bore.
and the oil ring (10) from the piston
(3) Turn the crankshaft (2, fig. 4-8) un-
til the piston (1) reaches the lowest
A l w a y s position the
p o s i t i o n of travel in the cylinder
chrome-faced top compression ring in
bore, then place a cloth on the piston
the first piston ring groove when pis-
head to collect the cuttings when the
ton rings are installed.
ridge is removed.
(4) Position a ridge cutter at the top of
(11) Remove the two retaining rings (12)
the cylinder bore, according to in-
from the piston pin bore in the pis-
structions furnished with the cutter,
ton. Then use a soft metal rod or pis-
and remove any ridges present.
ton pin remover and a hammer to
drive the piston pin (26) out of the
Caution: If the ridge is heavy, do
piston (11) and sleeve bearing (27)
not attempt to remove it all in one
in the connecting rod (13). Separate
cut. Take several small cuts, if neces-
the piston and connecting rod.
sary, to remove a heavy ridge.
Note. If the piston pin fit is excep-
(5) After the ridge has been removed, re-
tionally tight in the piston pin bore, use
move the ridge cutter from the top
an arbor press to remove the pin from the
of the cylinder bore. Then turn the
crankshaft until the piston reaches
(12) Use an arbor press to press the sleeve
the top of its stroke and carefully lift
b e a r i n g (27) from the end of the
out the cloth with the cuttings.
connecting rod (13).
(6) Again turn the crankshaft assembly
Note. The sleeve bearing should not
until the piston is at the bottom of its
be removed unless inspection indicates it
is worn or defective (b (9) below).
stroke. Remove the 2 stamped nuts
(4) and hex nuts (12) from the 2
b. Cleaning, Inspection, and Repair.
s h o u l d e r bolts (5) that secure the
(1) Clean all parts with an approved
connecting rod (3) to the crankshaft
cleaning solvent and dry thoroughly.
(2) Remove the carbon deposits from the
(7) The connecting rod and the rod cap
piston. Clean the piston ring grooves
(6) are both marked with an arrow
with a ring groove cleaner. Be sure
for assembly purposes.
the oil ring holes are clean.
to insure correct installation; then re-
(3) Inspect the pistion for cracks and
move the rod cap and the two shims
breaks at the skirt, pin bosses, and