Throttle Opening Vs. Fuel Flow; Throttle Slide; Main Jet - Polaris PREDATOR 50 2009 Manual

FUEL SYSTEM

Throttle Opening vs. Fuel Flow

In a full throttle condition the cross sectioned area between the
jet needle and the needle jet is larger than the cross sectioned
area of the main jet. The main jet therefore has greater control
over fuel flow.
Small
Clearance
Closed One-half
Throttle Throttle

Throttle slide

The throttle slide controls the rate of engine air intake by moving
up and down inside the main bore. At small throttle openings, air
flow control is performed chiefly by the cutaway. By controlling
air flow the negative pressure over the needle jet is regulated, in
turn varying the fuel flow.
Throttle Valve
Engine
Side
Higher cutaway number = leaner mixture
Throttle valves are numbered 1.0, 1.5, 2.0, etc., according to the
size of the cutaway. The higher the number, the leaner the
gasoline/air mixture.
4.6
Medium Large
Clearance Clearance
Full
Throttle
Air Box Side
Cutaway

Main Jet

When the throttle opening becomes greater and the area between
the needle jet and jet needle increases, fuel flow is metered by
the main jet. The number on the jet indicates the amount of fuel
CCs which will pass through it in one minute under controlled
conditions. Larger numbers give a greater flow, resulting in a
richer mixture.
Mikuni Main Jet
Larger Number = Richer Mixture
(50cc)
Keihin Main Jet
(90cc)