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ENGINE -
Carburetor
Note:
The regulator will not operate while the engine is at
rest.
Therefore, it
is
necessary
to
turn the adjusting
screw
about 6 turns
into
pump body 3 before start-
ing
the engine, keep the engine idling, and adjust the
fuel level.
Be sure
to
keep the cap placed on the fuel
level
pipe
while
driving
.
(3)
The throttle stop
screw,
pilot screw, slow
jet.
partial
jet,
and main adjusting screw are set at the factory
so that they match the operation on level land in
winter.
Therefore, these screws and jet may require read-
justments depending on geographical conditions.
1) Idle speed adjustments
Idle-speed
adjustments
must be made with the pilot
screw
(to
regulate the mixture) and the throttle stop
screw (to regulate the idling speed) so that the en-
gine idles smoothly.
Whether or not engine idle mixture
is
correctly ad-
justed will
'
also affect the starting and acceleration of
the engine.
The
pilot screw should
be
backed off 1-
3/8 turns from a lightly seated
position
.
With the pilot screw in this position
,
the mixture will
be slightly richer.
Throttle
stop screw
adjustment
Fig
.
2-39
Pilot
screw adjustment
Fig. 2-40
2) Procedure for adjustment
.
a) Set the pilot screw and
the
main adjusting screw to
specification at the same time.
Settings at factory:
Settings at factory
GPX433F
Pilot screw
(L,
R)
1- 3/8
Slow jet
#45
Partial jet
#65
Main adjuster screw
(L,
R)
1
±
1/8
b)
Turn the pilot screw in or out 1/8 turn each
time,
until the engine
idles
fast.
c) Back out the
pilot
screw aditional 1/8
-
1/4
turn to
provide enough fuel for proper acceleration.
d) Perform a running test, and warm up the engine
again.
Then adjust
'the throttle
stop screw so that
the engine runs
at the specified
idling speed.
3) Slow jet and
partial
jet adjustments.
The #45 slow jet and
#
65
partial jet are installed at
the
factory, but if
the engine
will
not pick up speed
smoothly when
accelerated
at low altitudes, these
jets should be replaced
by
one step large
ones.
On
the
contrary,
if
the
engine runs
roughly, replace
with one step smaller ones.
Jets available
45
48
50
52
60
62
65
68
70
,
,
I
I
Slow jets
Partial jets
Note
:
Both slow jet
and partial
jet
are of
the
but have different
calibration numbers.
2
Slow
jet
".
--------..,.
same type,
2.
Partial
jet
Fig. 2-41
-22-
4) Main
adjusting screw adjustment.
The
main adjusting screw controls the mixture when
the snowmobile runs at speeds from medium to
high.
It should be adjusted so that the engine runs
smoothly with the richest possible mixture.
This is very important in order to prevent
the
engine
from overheating.
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