TM 54310-227-15
(10) Install the 2 shoulder bolts in the con-
ring grooves. Inspect for a scuffed or
necting rod. Position the rod cap on
scored condition around the skirt.
the connecting rod and secure with
(4)
Inspect the piston rings for damage
the 2 hex nuts, torqued to 18-foot-
and end gap. Measure the end gap
pounds. Then measure the inside dia-
with the piston ring compressed in the
meter of the connecting rod assem-
cylinder bore and parallel to the top
bly bearing surface. If the measure-
of the machined surface of the cylin-
ment is greater than 1.12900 inches,
d e r and crankcase block. Replace
without using shims, the bearing sur-
damaged piston ring or a ring having
face is worn excessively and the con-
an end gap greater than 0.022 inch.
necting rod assembly should be re-
Measure the end gap of replacement
placed. Measure the overall length of
rings in a similar manner and file the
the bearing to determine end play.
ends, if necessary, to obtain a mini-
The length should be 0.004 to 0.010
mum gap of 0.012 inch. Using a new
inch less than the length of the crank-
piston as a gage, measure the side
s h a f t journal between the journal
clearance between each of the piston
rings and their respective piston
shoulders. Reduce the length of an
oversize connecting rod assembly bear-
grooves. Proper side clearance is com-
ing by filing or grinding both sides
pression ring, 0.002 to 0.0035 inch;
of the assembly. If the end play ex-
compression and scraper rings, 0.001
ceeds 0.010 inch, replace the connect-
to 0.0025 inch; oil ring, 0.0025 to
ing rod assembly.
0.004 inch. Replace the complete ring
set if any one ring does not meet its
( 1 1 ) Inspect the crankshaft journal for
specified side clearance.
roughness, scoring, and wear. Mea-
(5)
Replace a piston showing signs of ex-
sure the journal for proper dimen-
cessive skirt clearance on ring side
sions as specified in paragraph 4-32.
c l e a r a n c e , cracks, breaks, or other
If all measurements are favorable,
damage. Measure the diameter of the
polish the journal with corcus cloth
piston. Replace the piston if the dia-
and clean thoroughly. Replace a worn
meter is less than 2.9960 inches.
or defective crankshaft (para 4-33).
(6)
Replace a piston pin showing signs
(12) Inspect the cylinder bore for cracks,
of fracture or wear. Measure the dia-
roughness, scoring, or signs or wear.
meter of the piston pin. Replace a
Measure the cylinder bore for proper
piston pin if the diameter is less than
dimensions. If the cylinder bore and
0.7497 inch.
piston wear are not excessive, new pis-
ton rings should perform satisfactori-
(7)
Inspect the connecting rod and rod
ly. Rebore or hone a cylinder having
cap for cracks and breaks. Inspect the
a slightly rough or scored, surface.
bearing seating surfaces for nicks,
burrs, and scratches. Repair or replace
(13) If the cylinder bore will not clean up
the connecting rod as necessary.
when bored or honed within the spe-
cified dimensions, the cylinder and
(8)
Inspect the shoulder bolts and nuts
crankcase assembly should be replac-
f o r cracks, breaks, and damaged
threads.
ed.
R e p l a c e faulty shoulder
bolts or nuts.
(14) If a glazed condition exists in a cylin-
der bore which is otherwise not de-
(9)
Inspect the sleeve bearing for scoring,
fective or worn, remove the glazed
scratches, and wear. Measure the in-
surface by passing a hone through the
side diameter of the sleeve bearing.
cylinder bore several times. Removal
Replace a sleeve bearing having an in-
of the glaze will aid in better setting
s i d e diameter larger than 0.75080
of piston rings.
inch.
4-27
