Cv Carburetor System Function (4 Cycle); Assembly, Cv Carburetor - Polaris Trail Boss 330 2003 Service Manual

FUEL SYSTEM/CARBURETION
CV CARBURETOR SYSTEM
FUNCTION
Carburetor Component Function
System Main
Components
Float Inlet Pipe,
System Needle and
Seat, Float,
(Level Control)
Float Pin
Venting Passages in
Carburetor,
Vent lines
to frame
Starter Choke Lever,
(Choke/En- Cable, Plung-
richment) er, Return
Spring, Carb
Passages
(Starter Jet,
Starter Bleed
Pipe)
Pilot Pilot Jet/
(Idle System) 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
Main Main Jet,
System Main Air Jet,
Main Air
Passage,
Needle Jet,
Jet Needle,
Vacuum
Slide,
Throttle
Plate
4.6
Main Main
Function Affect
Maintains All systems
specified All throttle
fuel level in ranges
float cham-
ber (carbu-
retor float
bowl)
Supplies All systems
atmospheric All throttle
pressure to ranges
float cham-
ber
Supplies All throttle
additional ranges
fuel air mix- Greatest
ture neces- effect at
sary for cold low throttle
starting settings
and idle
Primarily Mainly idle
supplies fuel to 1/4
at idle and throttle
low throttle Minimal ef-
positions fect after
1/2 throttle
Supplies 1/4 to full
fuel at mid- throttle
range and
high throttle
settings.
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.
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.
Low Pressure
Diaphragm
From Venturi
Throttle
Plate
= Air Flow
The chamber above the
Air Box
Pressure
From
Air Box
Vacuum
Slide
Venturi
= Low Pressure