FIG. A.lll/9 CHECKING PISTON DIAMETER AT
SKIRT BASE AND AT
50
mm.
(2
IN. APPROX.)
OFF
liners and pistons,
the
difference
being the run·
ning
clearance.
When
the
clearance exceeds the permissible
service
limits
(see
"Fits
and Tolerances" table)
the liners
must
be rebored (not
to
exceed
"B"
size) and new oversized
pistons
and rings in·
stalled.
Should
it
become necessary
to
replace the
pistons,
make sure
the
weight
of
the new ones is
within
a tolerance
of
:t
5 gr, (0.18 oz.).
A normal
piston
for
the
Model 360/460
Tractor
weights
930 gr. (32.8 oz.). For
the
510 Tractor, the
weight
is 999 gr. (35.2 oz.).
Piston pin bores
should
not be
out
of
round. If
so, replace them.
Install (and remove)
piston
rings
with
piston
ring
pliers
(Fig. A.lll/10) and arrange them
with
ends
staggered 120
o from each other. The second ring
(oil scraper) should be placed
with
the
word
"top"
in
the
up
position.
At
assembly,
the
end
gap
must
meet
specification
requirements (see table
of
data;
should
the
gap be
less
than
specified,
grind
the
ends, and
if
greater, replace
the
ring and
install
a
new one
of
the
same type.)
Using a feeler gauge,
check
the
ring side
clearance in
its
groove
to
be sure
that
it
meets
specified
requirements.
CONNECTING RODS
To remove
the
connecting
rods, proceed as
outlined
for
the
pistons,
Check
connecting
rod
squareness
with
a
fixture
(Item
b,
Fig. A.lll/12).
/
/
/
FIG. A.lll/10 INSTALLATION (REMOVAL) OF
SNAP RINGS WITH PLIERS
M. Skirt
class
Identification;
N. Weight
of
piston
In grams
FIG. A.lll/11 FITTING A PISTON INSIDE ITS
CYLINDER LINER WITH PISTON RING COM·
PRESSOR
The
maximum
permissible
misalignment
bet·
we.en
connecting
rod
big
and small end axis,
checked
at
4.921
in. (125 mm.) away from
the
rod
center
line,
should
not
exceed 0.010 in. (0.05
mm.) in
either
direction.
Besides,
the
new rods
must
be stamped
with
the
number
of
their
locating
cylinder. The figure is
stamped on
both
the
body
and bearing cap
of
the
connecting
rod (Item G, Fig. A.lll/12).
If
new bearing
bushings
are
to
be
fitted
into
the
rod small end, then re-bore
it
with
an expansion
blade type reamer
to
the
diameter
indicated
in
the
"Fits
and
Tolerances"
table.
Engine·
27
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