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3.
E N
G I
N E - - - - - - - - - - - - - - - -
3-7
TRANSMISSION
A.
Construction
The transmission transfers power from the engine to the drive sprocket and changes the
torque by means of engaging gears having different numbers of teeth.
As shown
in
Fig.
3-46, when the driving gear is small and the driven gear is large,
the number of rotations
of the driven shaft is small and a
larger torque
is
transmitted.
The
ratio of
teeth in
engag-
ing gears is
termed
the "reduction ratio"
.
Fig. 3-47
shows the number
of
teeth
in each
gear of
the Honda
90 transmission.
There are two
types of
gearing generally used for motorcycles,
the
selective
slide
type and the constant mesh
type.
In
the selective
slide
type, the
gear
shift fork
slides
a
shift gear to
engage
with different gears
and
change the reduction ratio.
In
the
constant
mesh system,
pairs of
gears are always
engaged
and permitted to rotate
freely,
and
by
action of the gear shift mechanism different pairs
of gears
are bound to
the
driven
shaft,
obtaining different reduction
ratios.
The Honda 90
utilizes
a 4-speed constant mesh
transmission which transmits the output
of the engine into power for acceleration and hill climbing.
The six transmission gears mounted on the main shaft
and countershaft
are
fixed
by
splines
in
the
rotating d irection and
set
rings in the axial
direction.
B.
Operation
Low
Crankshaft power
is
transmitted to
the primary
driven
gear
through
the
c!utch.
The
driven
geOI" is
spline-connected
to the
transmission
main
shaft and power
is transferred
to
the countershaft
low
gear from the main
shaft.
The countershaft low gear rotates
freely
but
when
the
spline-connected
countershaft
second
gear is
shifted
by the
gear
shift fork
towards
the low
gear
the
second gear
dowel fits into the
cowel
hole
on
the
low
gear
and binds the
low
gear to
the
countershaft
through the second gear
and power is transmitted
to the drive
sprocket
fitted on the
left
end of
the
counter
shaft.
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