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ENGINE -
Carburetor
10) Check the metering needles on the ends of main
adjusting screw and slow adjusting screw.
If
any
needle
is
damaged, the needle seat is considered to
be
scratched
.
Replace the carburetor
body.
11) Check the idle bypass hole for clogging
.
If clogged,
clean with compressed air.
Never
use a wire
.
12)
Check the main nozzle for clogging, and if necessary,
blow with compressed air.
13)
Check the starter shaft.
If the shaft is bent, replace.
14)
If the main adjusting screw G-ring is scratched or
broken, replace together with the main adjusting
screw.
2 -5 -4
.
Assembly
(GPX338F)
Reverse the procedure
for
disassembly
Note:
D
Take care so that the main diaphragm is installed in
the correct position.
Fit the main diaphragm
rim
to
the pump body flange.
D
The throttle mechanism should not be
disassembled
.
D
When assembling, be careful not to reverse
the
posi-
t ion of gaskets.
Carburetor
fa
ilures
are often caused
by dust
and
incorect service.
D
Be careful not to install the
pr
imary
venturi in the
opposite
direction.
Be sure to align
the
nozzle with
the hole in the
carburetor
body.
2-5-5.
Installation (GPX338F)
For installation,
reverse
the procedure
for removal.
No tightening torque for
carburetor
mounting nuts
can
be specified
for
reason of its construction, and
therefore, they should be
carefully
tightened with a
wrench.
2-5-6
.
Adjustments
(GPX338F)
(1)
The carburetor
is
properly adjusted and subjected to
a stringent test at the factory, and therefore,
it
shou
ld
not be disassembled or adjusted unnecessari-
ly.
However, according to operating conditions or geo-
graphical conditions (weather, altitude, etc.), it may
require readjustment. cleaning and inspection.
In
this case the following parts must be readjusted
.
1)
The slow adjusting screw to control
the
mixture
when the engine idles.
2) The throttle stop screw to control the idling speed.
3) The main adjusting screw to control the mixture
when throttle opening
is
larger.
4) The pilot
jet
to control the speed from idling to me-
dium range for smooth acceleration.
(In this range,
the mixture can not be requlated by the slow adjust-
ing screw and the main adjusting screw.)
(Fig.
2
-
31 )
4
2
1.
Throttle stop screw
3.
Pilot screw
2
.
Slow adjusting
screw
4.
Ma in
adjusting
screw
F
ig.
2·31
5) Adjusting
the
throttle
stop screw
,
s low adjusting
screw and main adjusting
screw.
The
slow adjusting screw, pilot
jet
and the main ad
-
justing screw
are
set
at
the factory so that they
match
the
operation
on level land
in winter.
There
-
fore,
the
jet and screws may require readjustments
depending
on
geographical
conditions.
(2) Idle-speed adjustments
Idle-speed adjustments must
be
made with the
slow
adjusting screw
(to
regulate.
the mixture) and the
throttle stop screw
(to regulate
the idling speed) so
that the engine idles smoothly.
Whether
or
not engine idle
mixture is correctly ad
-
justed
will
also
affect the starting
and acceleration of
the engine
.
The
sl
ow adjusting
screw should be
backed
off
1-3/
8
turns from a
lightly seated position
.
With
the slow adjusting
screw
in
this position, the
mixture
will be slightly richer.
(Fig.
2-32,
2-33)
Throttle
stop screw adjustment
/ '
)
-
Fig.
2-32
-18
-
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