Float Mechanism; Idle, Intermediate And Main Fuel Systems - Arctic Cat Cougar Service Manual

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The carburetors installed on these models con-
tain several major systems. A float and float
valve mechanism are used to maintain a constant
fuel level in the float bowl. The idle mixture
system controls the amount of fuel at low engine
speeds. The main fuel system controls the
amount of fuel at high speeds. At intermediate
engine speeds, the fuel is controlled by the nee-
dle jet and its jet needle. A starting enrichment
(choke) system is incorporated in the carburetor
to supply the rich mixture necessary for starting
a cold engine.
Float Mechanism
The carburetor is equipped with a float valve.
The fuel inlet valve (Figure 3) is attached to the
float and moves up and down with the float.
Movement of the fuel inlet valve in relationship
to the inlet valve seat opens and closes the fuel
inlet valve to maintain a steady supply of fuel at
a constant height in the float bowl. Fuel is sup-
plied to the float valve by a pulse-operated fuel
pump.
Idle, Intermediate and Main Fuel Systems
The purpose of the carburetor is to atomize
fuel and mix it in correct proportion with air
throughout the entire speed range. At small throt-
tie openings (from idle to about 118 open), only
a small amount of fuel is mixed with a small
CHAPTER SIX
amount of air. A typical idle mixture system is
shown in Figure 4. The pilot air screw controls
a small amount of air mixed with fuel from the
pilot jet. Opening the pilot air screw (sometimes
called an idle mixture screw) permits more air to
enter the idle mixture system and leans the mix-
ture.
As the throttle is opened further, more air
enters the engine around the throttle slide as
shown in Figures 5 and 6. Fuel is drawn into the
air stream through the needle jet. The jet needle
limits the amount of fuel flowing through the
needle jet.
Air
Fuel
Inlet valve seat
Fuel inlet valve
Pivot
Float bowl
CARBURETOR OPERATION
(Throttle Opening 0 to 1/8)
Pilot outlet