Polaris Outlaw 500, Service Manual

Page: 100 / 202

4.5
FUEL SYSTEM / CARBURETION
4
CV CARBURETOR SYSTEM
Carburetor Function
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 Carburetor 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.
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
chamber
(carburetor float
bowl).
All systems; all
throttle ranges
Venting
Passages in
carburetor; vent
lines to frame.
Supplies
atmospheric
pressure to float
chamber.
All systems; all
throttle ranges.
Starter
(Choke /
Enrichment)
Choke Lever, Cable,
Plunger, Return
Spring, Carb
Passages (Starter
Jet, Starter Bleed
Pipe).
Supplies additional
fuel air mixture
necessary for cold
starting.
All throttle
ranges.
Greatest effect
at low throttle
settings 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 effect
after 1/2
throttle.
Main System
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.
Throttle Plate
Diaphragm
Low Pressure
From Venturi
Atmospheric
Pressure
Air inlet
Atmospheric
Vacuum
Slide
Venturi
= Air Flow
= Low pressure