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Throttle Valve
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. The higher the
number, the leaner the gasoline/air mixture.
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.
Main jets are screwed directly into the needle jet base.
4/99
FUEL SYSTEM/CARBURETION
Component Functions (2 Cycle)
Throttle Valve
Engine Side
Higher cutaway number = leaner mixture
Mikuni Hex
Style Main Jet
Larger Number = Richer Mixture
4.9
Air Box Side
Cutaway
Main Jet
Polaris
Sales Inc.
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