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TM5-4210-229-14&P
6-12. PISTON AND CONNECTING ROD MAINTENANCE (Continued).
(2) Clean all carbon from the piston ring
grooves; using a nonmetallic brush. Be sure
all oil holes in the piston are open.
(3) Visually inspect the pistons for scuffed or
scored skirts and cracked or worn piston
ring lands. Replace the piston if necessary.
(4) Check running clearance between the pis-
ton and cylinder sleeve (with piston rings
removed) for piston skirt wear. Measure at
the largest piston diameter. If running
clearance exceeds 0.0065 in (0.165 mm)
replace the piston.
(5) Visually inspect the piston pins for wear.
Replace any pins which show signs of corro-
sion or etching.
CAUTION
Faulty rings cannot always be detected by the
eye. Therefore, whenever a piston is
removed from a cylinder, it is recommended
that the piston rings be replaced.
(6) Visually inspect new rings for any signs of
damage prior to installation.
(7) Proper ring gap check.
(a) Push the ring down into a new cylinder
sleeve with a piston. (This will position
the ring squarely in the sleeve).
(b) Measure the gap between the ends of
the ring with a feeler gauge.
(c) Ring gaps should be 0.016 to 0.29 in
(0.41 to 0.74 mm). If ring gaps are not
within limits, replace the rings.
(8) Install new rings in the piston grooves with a
suitable ring installing tool.
NOTE
The number 1 (compression ring) will have the
word top stamped on the ring.
The number 2 (intermediate ring) will be
marked top, up, or with a pip on the top side of
the ring.
(9) Inspect the windows of the oil regulating
rings for blocked oilways.
CAUTION
Failure to keep the oilways clear will result in
uneven lubrication of the piston and sleeve.
(10) All rings must fit loosely in the piston ring
grooves without binding.
(11) Ring bearing surfaces must be of a smooth
satin like finish with no burrs. Visually in-
spect new. rings, prior to installation, for
burrs.
CAUTION
When new rings are being installed on a used
piston for operation in a used sleeve, wear on
the sleeve may have left a ridge where the pis-
ton reaches the top of its stroke. This ridge will
cause noisy engine operation and breakage of
the top ring. Remedy this by removing the ridge
before installing the piston ring.
d. Cylinder sleeves inspection.
(1) Using a soap solution clean the cylinder
sleeves with minimally abrasive brush.
(2) Thoroughly clean the O-ring groove in the
sleeves.
6-32
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