Piston / Throttle Valve; Jet Needle/Needle Jet; Jet Needle; Needle Jet - Polaris 340 LX 2007 Service Manual

Fuel System
selecting the proper main jet always use the lowest
elevation and temperature that is likely to be
encountered.
CAUTION
A main jet that is too small will cause a lean operation
condition and may cause serious engine damage. Jet
the carburetors carefully for elevation and temperature
according to the jetting charts in the Specifications
Chapter of this manual or the models' Owner's Manual
Supplements.

Piston / Throttle Valve

INTAKE SIDE
The throttle valve 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 valve is regulated, in turn varying the fuel flow.
The throttle valves are numbered 1.0, 1.5, 2.0, etc.,
according to the size of the cutaway in millimeters. The
higher the number, the leaner the gasoline/air mixture.
4.6

Jet Needle/Needle Jet

The jet needle and needle jet have the most effect
between 3/8 and 3/4 throttle opening. Some mixture
adjustment can be accomplished by changing the location
of the "E" clip on the needle. Moving the clip down raises
the needle in the jet passage and enriches the mixture.
Moving the clip up lowers the needle in the jet passage
and leans the mixture. Letter and number codes are
stamped into the needle and the jet indicating sizes and
tapers (taper of needles only) of each.

Jet Needle

The jet needle tapers off at one end and the clearance
between the jet needle and the needle jet increases as the
throttle valve opening gets wider. The air/fuel mixture ratio
is controlled by the height of the "E" ring inserted into one
of the five slots provided in the head of the jet needle.

Needle Jet

The needle jet works in conjunction with the jet needle.
9923396 - 2007-2012 EDGE/Widetrak LX Service Manual
©2011 Polaris Sales Inc.