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42
3.
E
N
G I
N
E
----------------------------
3-8
CRANKCASE
A.
Construction
The
die cast
aluminum a!loy crankcase which
also
contains
the transmission
gears can
be
split into
right and left
halves.
Stud
bolts for
fitting
the cyl
inder,
cylinder
head and cylinder head cover are provided
on the
front
port
of
both right
and left crankcases.
A breather chamber is provided
in
the
front upper section and
with
its
labyrinth,
pressure
inside the
crankcase is discharged through
the right
crankcase.
An oil
strainer
is
fitted
in the front
lower
section
of the right crankcase.
B.
Disassembling
Separate the
right
crankcase from the
left
crankcase as
described
in 3-7 D,
leaving the
oil strainer
and
shift
return
spring installed
in the
right crankcase and
the
oil pump and neu-
tral
switch
contact in
the
left
crankcase.
C.
Assembling
l
.
P:ace
crankshaft assembly in
left crankcase.
CAUTION
New gaskets
must
be
used
each
time the engine
is
disasse mbled.
D.
Operation
of
Breather
The inside of
the
crankcase
is
subject to
pressure
nuctuations
due to the reciprocating
motion of
the piston.
It also
fills w ith
combustion
gas
leaked around
the
piston
and
other
gases
generated
by
high
temperatures.
Contamination
and
deterioration of lubrication
oil
is
hastened and the oil is liable
to
leak from joints
because
of
the internal
pressure
in
the
crankcase.
The breather is provided to discharge these gases and re!eave
the
pressure
in-
side
the
crankcase.
As
shown
in
Fig.
3
-
58,
the
breather
is
located
in
the
front
upper sections
of
the
right
and left crankcases and discharges
through
a labyrinth throuth the
right
crankcase.
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