M.l
ENGINE
BODY
68 mm
STROKE
SERIES
WSM,
01
160
I
0087F011
I
[3]
CRANKSHAFT
The crankshaft with the connecting rod converts
the reciprocating motion of the piston into the
rotating motion.
The crankshaft
is
made of tough special alloy
steel,
and the journals, pins and oil
seal
sliding portions are
induction hardened to increase the hardness for
higher wear resistance.
The front journal
is
supported by
a
solid type
bearing, the intermediate journal by
a
split type, and
the rear journal by
a
split type with thrust bearings.
The crankshaft
is
provided with an oil gallery,
through which engine oil
is
fed to the crank pin
portion, and lubricate
it.
[4] PISTON AND
PISTON
RINGS
0109F017
[5]
CONNECTING ROD
The piston
is
made of aluminum alloy.
Two
recesses for
the
valves
are provided on top of
the piston.
A
fan-shaped depression
is
also given
atop the piston in order to allow combustion gas to
jet smoothly. The piston pin
is
slightly out of the
center of the piston.
In
this
design, the run-out of the
piston
at
the top and bottom dead points
can
be
reduced, thereby resulting in lower operating noise.
The piston has
a
slightly oval shape when cold (in
consideration of thermal expansion) and
a
concave
head.
Three rings are installed in grooves in the piston.
The top ring
(1)
is
a
keystone type, which
can
stand
against heavy loads, and the barrel
face
on the ring
fits well to the cylinder wall.
The second ring
(2)
is
an
undercut type, which
effectively prevents the oil from being carried up.
The
oil
ring
(3)
has chamfered contact
faces
and an
expander ring, which increase the pressure of the oil
ring against the cylinder wall.
Several grooves are cut on
the
topland to help
heat
dissipate and to prevent scuffing.
(1)
TopRing
(2)
Second Ring
(3)
OilRing
(4)
Fan-Shaped Concave
(5)
Valve Recess
Connecting rod
(2)
is
used to connect the piston
with the crankshaft. The big end of the connecting
rod has
a
crank pin bearing
(3)
(split type) and the
small end has
a
small end bushing
(1)
(solid type).
(1)
Small
End
Bushing
(2)
Connecting
Rod
(3)
Crank pin Bearing
0
109F018
M-5
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