Remove dirt and deposits from the piston surfaces
with an approved cleaning solvent. Clean the piston
ring grooves with a groove cleaner or the end
of
a
piston ring filed to a sharp point (Figure
65).
Care
must be taken not
to
remove metal from the groove
sides or bottom.
Do
not use
a
caustic cleaning sol-
-
venf or wire brush for cleaning
pisfons. These materials will cause pisfon damage.
FIGURE
65.
PISTON GROOVE CLEANING
When cleaning the connecting rods in solvent, in-
clude the rod bore. Blow out all passages with com-
pressed air.
Engines that have been fitted with
0.005
inch
(0.13
mm) oversize pistons at the factory are identified by
the letter
E
after the serial number. Number is
stamped on the cylinder block and on the unit
nameplate.
Inspection
The following text contains inspection procedures
concerning pistons and connecting rods.
Piston Inspection:
1.
Inspect the pistons for fractures at the ring lands,
skirts, and pin bosses. Check for wear at the ring
lands, using a new ring and feeler gauge as
shown in Figure
66.
Replace the piston when the
side clearance of the top compression ring
reaches
0.008
inch
(0.20
rnm).
FIGURE
66.
CHECKING RING SIDE CLEARANCE
2.
Replace pistons showing signs of scuffing, scoring,
worn ring lands, fractures, or damage from pre-
ignition. Excessive piston wear near the edge
of
the
top ring land indicates pre-ignition.
3.
Proper piston tolerances must be maintained for
satisfactory operation.
4.
Refer
to
DIMENSIONS AND CLEARANCES
to
determine where
to
measure piston to be sure the
total clearance follows specifications.
.
0000
01
MEASURE CLEARANCE
HERE
+:
FIGURE
67.
MEASURING PISTON CLEARANCE
Connecfing
Rod
Inspection:
1.
Replace connecting rod boltsand nuts with darn-
aged threads. Replace connecting rods with deep
nicks, signs of fractures, scored bores or bores
out of round more than
0.002
inch.
2.
Use a new piston pin to check connecting rod for
wear.
A
push-fit clearance is required and varies
from engine to engine. If a new piston pin falls
through a dry rod pin bore as a, result of its own
weight, replace the rod.
47
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