CARBURETORS (Con't.)
DEGREE
OF OPENING:
1/8-
1/4,
air
screw,
throttle
valve
When
the cutaway
of
the
throttle
valve
is
made
larger, the
neg-
ative
pressure
which works on the needle
jet
reduces,
and
the
fuel-air mixture becomes
lean.
When
the cutaway
of
the
throttle
valve
is
made
smaller, the
negative pressure which works on the
needle
jet
becomes rich.
The cutaways
are
prepared at intervals
of
0.5
m/m
alternately.
(Note) The adjustment
of
the opening
can
be
made
either
by
the
throttle
valve
or
the air screw. However,
so
far
as
the idling
is
not
in disorder,
make
adjustment
by
the air
screw.
DEGREE OF OPENING:
1/4-
3/4, jet
needle
The
jet
needle
has
5
levels
of
groove.
When
the grip
goes
upward
(2nd
& 1st
levels)
the
space
between the
jet
needle
and
the
needle
jet
becomes smaller
and
the fuel-air mixture becomes
lean.
When
the grip
goes
downward, the
space
between the
jet
needle
and
the needle
jet
becomes larger
and
the fuel-air mix-
ture becomes rich.
DEGREE OF OPENING:
3/4-
full
open,
main
jet
When
the larger number
is
used,
the fuel-air mixture becomes
rich.
When
the smaller number
is
used,
the fuel-air mixture
becomes
lean.
CHECK AND ADJUSTMENT OF THE FLOAT SYSTEM
The overflow during driving or operation
of
the engine could
be
caused
by
a loose attachment due
to
worn needle
valves,
the
clog
of
dirt
and dust,
and
the malfunctioning
of
the float, etc.
Needle
Valve-
Worn.
Spring
is
damaged or worn - replace
with
a new
one.
Spring
seat
is
worn
or
scratched.
76
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