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c
c
c
3.
Cautions
3-1.
Crankcase and Relating Parts
a)
The crankcase
is
an
aluminum
alloy casting consisting of
two halves, the upper and lower halves, fastened
by
10 mm screws and 8 mm screws.
The
10 mm
screws should be tightened to 3.1·1.7
kg-m (22.4·26.8 ft·lb) torgue,
while the 8 mm
screws should
be
tightened
to
2.3·2.7 kg·m
(16.6
·
19.5 ft. - Ib.)
.
Be
sure to tighten these
screws
to
the correct
torque values when re-assembling
the engine.
b)
The
bore in the
crankcase
and
some other
parts have been machined at
our
factory after the upper and the
lower
casting halves have been
clamped together.
Never
assemble
two odd halves into one crankcase.
c)
When putting the upper
and the
lower half
crankcase castings together,
first temporarily tighten the screws,
after putting
the crankshaft
into
position, then strike
lightly
on
the drive
shaft
to drive the
crankshaft
towards the
fan
side, before
finally tightening the
screws to
the
specified
torque.
If the crankcase castings are clamped together
with
the crankshaft shifted towards the drive shaft end,
when the
crankcase
rear
cover
is fastened, the rear
cover
will
push
the
bearing outer race
sidewise,
resulting in burning
of the
bearing when the
engine
starts.
Strike
lightly before
tightening the
cap
screws
(for
upper
and
lower crankcase)
to the specified
torque.
Make
adjustment by inserting packings
of suitable
thickness.
Figure
1
3- 2.
Crankshaft, Connecting Rod and Relating Pans
a)
The
crankshaft
is
composed of
individually machined parts made
of carbon steel,
viz.
one
front
crankshaft,
two central crankshafts, one rear crankshaft,
two
crank pins,
two
needle
bearings for
connecting
rod large
ends,
two connecting
rods,
one
intermediary
bushing and
five ball bearings,
built
into
one
piece using
a
precision fixture.
On the
front
part of the crankshaft is
built
a magnetogenerator
while the
rear part serves as
the
output shaft.
Dis-
assembling and re-assembling of the crankshaft
into individual
components is only
possible
at our
factory.
When-
ever a crankshaft
needs
to be replaced, an assembled complete crankshaft must
be
exchanged as
whole.
b)
The tightening torque for the magnetogenerator
fixing nut is
66 ft-Ibs.
3-3.
Cylinder and Cylinder Head
Made
of an aluminium alloy casting,
with
good
heat
conductivity, the cylinder contains cast
iron liners, integrally
cast
in
it. The
liners
are precision castings made of special alloy cast iron, the
bores
are finished
by honing
so that they
with-
stand wearing and preserves gas-tight contacting with the piston rings
which
move inside.
28
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