Main System - Polaris 2009 Trail Boss 330 Service Manual

FUEL SYSTEM/CARBURETION

MAIN SYSTEM

As throttle valve (1) is opened, engine speed rises,
and this increases negative pressure in the venturi.
Consequently the vacuum slide (2) moves upward.
The fuel in float chamber (3) is metered by main jet (4),
and the metered fuel enters needle jet (5), in which it
mixes with the air admitted through main air jet (6) to
form an emulsion. The emulsified fuel then passes
Pilot Screw location
through the clearance between needle jet (5) and jet
needle (7), and is discharged into the venturi (A).
Mixture proportioning is accomplished in needle jet
(5); the clearance through which the emulsified fuel
must flow is determined ultimately by throttle position
and vacuum slide height.
Brass Plug Installed
1
2
Brass Plug Removed
7
A
6
3
5
4
PILOT SCREW
The pilot system supplies fuel during engine operation
with the throttle valve closed or slightly opened. The
fuel/air mixture is metered by pilot screw and
discharged into the main bore through the pilot outlet.
CAUTION:
The pilot screw is calibrated at the factory to meet EPA / CARB
regulations for air quality standards and is sealed with a brass
plug to prevent tampering. Removal of the tamper proof plug
is not permitted. For service purposes, cleaning of the pilot
circuit can be done only by a certified repair shop to ensure air
quality standards are not exceeded.
4.9