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 (d) Coat the piston pin (5) with prussian
(4) Lift the scraper rings off their spaces on
blue. Insert piston pin into sleeve bearing, then rotate
sleeve marking them for installation in same space in
the pin back and forth through one-quarter turn.
the event they are re-used.
Remove the pin.
(5) Clean rings and sleeve with clean fuel oil,
(e) Inspect the bottom surface of the sleeve
then remove all accumulated carbon. Inspect the rings
bearing for blue marks. When a minimum of 67 percent
and sleeve for abnormal wear, breaks, or cracks.
of bottom bearing surface shows blue, the piston pin is
Replace defective cylinder and sleeve assembly. or
properly fitted. If less than 67 percent shows blue, it
rings.
must be scraped and fitted.
(6) Install the rings on sleeve (see notes and
cautions above), align scribe marks, then position
NOTE
sleeve in cylinder.
In addition to scraping for fit, when
(7) Secure flange to cylinder with six nuts (1).
fit is attained, it must be aligned with
(8) Install piston and connecting rod, then
the foot of the connecting rod. This
install oil outlet pipe to bottom of cylinder.
may require scraping of the bearing
NOTE
to assure pin and foot are horizontal
Be sure that oil baffle is in place on
with each other.
bottom of cylinder.
(f) Use a machinists scraper, and scrape
e. Cleaning, Inspection, and Repair of Piston and
away the blue from bearing surface, a little at a time.
Rod.
Repeat the marking and scraping process until bearing
(1) Use a soft metal bar, the same width as
is fitted.
the piston rings, to pry out frozen rings.
(g) Place fitted pin in sleeve bearing of
(2) Use a soft metal scraper (or a piece of
connecting rod. then stand connecting rod on its foot.
broken ring with edge ground blunt) to remove hard
or use a straight edge across the foot, and measure the
carbon from ring grooves in piston.
distance from foot to each end of the piston pin Unless
(3) Wash piston inside and out with clean fuel
both sides measure exactly the same. the high side
oil. Wipe dry with a lint free cloth and blow clean with
must be scraped off of bearing surface until the
ships service air.
distances match.
(4) Use a wire brush to remove carbon from
(10) After the sleeve bearing has been fitted,
crown of piston. Wash in clean fuel oil and wipe dry
use the dowel pin hole in rod eye as a guide, drill holes
with a lint free cloth.
in bearing for new dowel pins, and insert the pins.
(5) Inspect top (crown) of piston for cracks.
Blows away all drill chips with compressed air.
Replace a defective piston.
(11) Wash piston rings in clean fuel oil and
(6) Wash the connecting rod in clean fuel oil
remove all carbon.
and wipe dry. Use a rod or wire to remove any
NOTE
obstructions from lubricating oil passages in the rod,
Piston rings that were stuck in
then blow passages clean with compressed air. Start air
groove are worn thin on one side,
through passage from the foot of the rod, up to the
and must be replaced.
piston pin sleeve bearing.
(12) Use a micrometer and measure ring
(7) Wash the piston pin in clean fuel oil and
thickness. Replace a damaged or worn ring.
wipe dry with a lint free cloth.
(13) Place the five rings for a cylinder in the
(8) Insert piston pin in piston pin sleeve
cylinder one at a time, and measure the end gap.
bearing. Use a feeler gage to measure clearance from
Proper gap should be between 0.085 and 0.090 inch. If
top of pin to bearing. This clearance should be between
ring gap is less than 0.085 inch, file the ends a little at a
0.004 and 0.006 in. When clearance is more than 0.008
time, until proper gap is attained. Replace a ring with
in., check the piston pin diameter at ends and center for
more than 0.090 inch end gap.
a measurement of between 5.493 and 5.494 inch., If
(14) When new rings are to be used. check as
piston pin is worn, or out of round; or the diameter is
in (13) above.
less than 5.488 inch, replace the piston pin. If piston pin
f. Installation.
meets requirements, replace the sleeve bearing.
(1) Install the connecting rod and piston pin to
(9) To replace a piston pin sleeve bearing,
the piston in reverse order of their removal.
proceed as follows:
(2) Using a ring expander, expand rings only
enough to get them over the piston. Install rings in
hold sleeve bearing in position.
groove from which removed, then remove tags.
(b) Drive or press the old bearing (4) out of
Stagger the end gaps 900 to prevent blow-by.
the connecting rod (11).
(3) Hoist piston over the cylinder from which
(c) Scribe a mark on the new sleeve
it was removed. Check that the connecting rod foot is in
bearing through the center of the lubricating oil hole.
position relative to bearing box.
Align this scribe mark with the oil hole in the connecting
(4) Place the connecting rod guides (table 4-
rod. Press the sleeve bearing into the connecting rod.
Make a check to assure that both holes are lined up.
3-31
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