FUEL SYSTEM
Carburetor
Page 14-4 2001 Pioneer 900 Gasoline Vehicle Maintenance and Service Manual
14
CHOKE AND FRESH AIR SYSTEM
The choke system aids in starting the engine in cold weather. When starting a cold engine, the choke cable
handle (1) (Figure 14-4, Page 14-4) is pulled. This restricts the air flow to the venturi, causing a very high
vacuum that draws fuel into the venturi at a high rate and thus creates a “fuel rich” mixture. The choke handle
is pulled until the engine starts, and then released when the engine begins to run smoothly.
An air duct provides the engine with clean, cool air from outside the engine compartment. This feature
increases engine horsepower and greatly extends air filter life.
FLOAT SYSTEM
The carburetor is a float bowl type, with the float chamber located just below the carburetor body. The float sys-
tem keeps the fuel in the float chamber at the correct level while the engine is running (Figure 14-5, Page 14-4).
Fuel is supplied to the carburetor float chamber by an external impulse pump that draws fuel from the fuel
tank and through the fuel filters (Figure 14-4, Page 14-4). The fuel then passes through the inlet valve (5)
and into the float bowl. The fuel entering the bowl causes the float (4) to rise until it shuts off the inlet valve,
preventing the fuel from exceeding a level predetermined by the float level setting.
CARBURETOR
Read DANGER and WARNING on page 14-1.
Before suspecting the carburetor as the cause of poor engine performance, make sure the fuel and ignition
systems are in proper operating condition. Check the following items:
• Spark plug and gap condition. See Spark Plug, Section 13, Page 13-6.
• Air filter element. See Air Filter on page 14-18.
• Fuel filters. See Fuel Filters on page 14-18.
• Choke and air intake system (for restriction of air flow). See Choke and Air Intake System on
• Fuel pump. See Fuel Pump on page 14-19.
Figure 14-4 Choke System
Figure 14-5 Float System
4
2
8
6
5
3
1
FUEL
CARBURETOR
AIR
AIR
SIDE VIEW
END VIEW
FUEL
FUEL
LEVEL
FLOAT
AIR / FUEL MIXTURE
FUEL
INLET
FUEL
NEEDLE
VALVE
