Polaris PREDATOR 2003, Service Manual

Page: 94 / 193

FUEL SYSTEM/CARBURETION
4.5
CV CARBURETOR SYSTEM
FUNCTION
Carburetor Component Function
System Main
Components
Main
Function
Main
Affect
Float
System
(Level Control)
Inlet Pipe,
Needle and
Seat, Float,
Float Pin
Maintains
specified
fuel level in
float cham-
ber (carbu-
retor float
bowl)
All systems
All throttle
ranges
Venting Passages in
Carburetor,
Vent lines
to frame
Supplies
atmospheric
pressure to
float cham-
ber
All systems
All throttle
ranges
Starter
(Choke/En-
richment)
Choke Lever,
Cable, Plung-
er, Return
Spring, Carb
Passages
(Starter Jet,
Starter Bleed
Pipe)
Supplies
additional
fuel air mix-
ture neces-
sary for cold
starting
All throttle
ranges
Greatest ef-
fect at low
throttle set-
tings and
idle
Pilot (Idle
System)
Pilot Jet/
Passage-
ways, Pilot-
Mixture
Screw with
Spring
Washer and
Sealing O-
Ring, By-
pass Ports
(Behind
Throttle
Plate), Pilot
Air Jet, Pilot
Outlet,
Throttle
Plate
Primarily
supplies fuel
at idle and
low throttle
positions
Mainly idle
to 1/4
throttle
Minimal ef-
fect after 1/2
throttle
Main Sys-
tem
Main Jet,
Main Air Jet,
Main Air
Passage,
Needle Jet,
Jet Needle,
Vacuum
Slide,
Throttle
Plate
Supplies
fuel at mid-
range and
high throttle
settings.
1/4 to full
throttle
VENT SYSTEMS - CV
CARBURETOR
The carburetor float bowl vent lines supply
atmospheric pressure to the float bowl. The lines
must be free of kinks, restrictions and be properly
routed. This allows fuel to flow in the proper amount
and prevents contaminants from entering the
carburetor.
MIKUNI CV CARB
OPERATION
The constant velocity carburetor incorporates a
mechanically operated throttle plate and a vacuum
controlled slide valve (vacuum slide). The venturi
cross-sectional area in the carburetor bore is
increased or decreased automatically by the vacuum
slide, which moves according to the amount of
negative pressure (less than atmospheric) present in
the venturi.
A diaphragm attached to the top of the vacuum slide
is sealed to the slide and to the carburetor body
forming two chambers. The chamber above the
diaphragm is connected to the venturi area by a drilled
orifice in the center of the vacuum slide. The chamber
below the diaphragm is vented to atmospheric
pressure by a passage on the air box side of the
carburetor. A spring, installed in the center of the
vacuum slide, dampens the slide movement and
assists the return of the slide.
= Air Flow
= Low Pressure
Air
Pressure
From At-
mosphere
Venturi
Throttle
Plate
Diaphragm
Vacuum
Slide
Low Pressure
From Venturi
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