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3.
E
N G I N E
3-5
RIGHT CRANKCASE COVER
A.
Construction
The diecast aluminum alloy right crankcase cover has oil inside at the same level as in
the
crankcase and is equipped with an oil level gouge.
An
o
il
passage for supplying
lubrication
oil from
the
oil pump through
the
crankca
se
to
the
cylinder head, gear engagements, clutch cover and crankshaft is
provided.
A drain plug is installed in the lower front part of
the
cover.
B.
Construction and Operation of Clutch
A clutch is
located
between
the
engine and transmission to transmit power
or
break the
power transmission as needed
for changing
speeds, starting engine, etc. Important points are
the degree of engagement perfection,
ability
to
disengage
completely,
smoothness
of
enga
-
gement and
disengagement,
lack
of
drag when
disengaged
and lock
of slippage
when
engaged.
There are several types of clutches such as cone, centrifugal,
single-plate,
multi
-
plate,
etc.
These are
further classified
into
wet type
and dry
type,
with
the
former having the
clutch mechanism immersed in an oil bath and the latter not having oil inside the clutch.
The Honda 90 clutch is a wet multi-plate type
.
As shown in
Fig.
3-29
and
Fig.
3-
30,
the clutch outer case is located beneath the right crankcase cover.
The clutch is made
up
of
clutch springs,
drive
plate,
clutch plates and friction
discs.
The
friction discs
have
teeth
inside
to fit to
the
clutch center so
that they
revolve w ith
it.
The clutch plates have
dog teeth on the outer
edges so
that they fit
into
the clutch housing and turn with it, along
with the drive
plate.
The drive plate
has
grooves on the
inside
which
fit it
to
the
crank-
shaft,
which the
drive center
engages with the drive
gear by the clutch center guide and
can rotate
freely on
the
crankshaft.
When
the
clutch
lever on
the handlebar
is
pulled, the
clutch
wire pulls
the
clutch lever
fitted to
the clutch
assembly,
working
against the
clutch
springs to free the
friction
discs and clutch plates from
one
another
.
When it
is
rel eased,
the force of the clutch springs pushes
the
friction
discs
and clutch plates together so that
they
rotate together
from
friction, transmitting
the
rotation
of
the
crankshaft
through the drive
plate, clutch
plates,
friction discs,
clutch
center,
drive gear and primary driven gear to the
transmission
gears.
A damper
spring
prevents
noise
in
the
clutch and
keeps
the teeth from
breaking.
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