WM 130/170/270 Repair Sub Systems
wc_tx000382gb.fm 81
10.3 Carburetor
Specifications
Float System
The float chamber is located below the carburetor body. Through the
operation of the float and the needle valve, the float chamber maintains
a constant fuel level while the engine is working. The fuel flows from
the tank into the float chamber through the needle valve. When the fuel
rises to a specific level, the float rises. When the buoyancy of the float
is balanced with the fuel pressure, the needle valve shuts off the fuel
passage, thereby maintaining the fuel at the predetermined level.
Pilot System
The pilot system supplies fuel to the engine during idling and low-
speed operation. Fuel is initially metered by the main jet and then
metered once again by the pilot jet. At the pilot jet, the fuel is mixed with
air metered by the pilot air jet and then the fuel/air mixture is fed to the
engine through the pilot outlet and the bypass. During idling, fuel is fed
to the engine mainly through the pilot outlet.
Main System
The main system feeds fuel to the engine at medium and high speed
operation. Fuel is metered by the main jet and flows into the main
nozzle. Air metered by the main jet is mixed with fuel through the bleed
holes of the main nozzle. The fuel/air mist is injected into the Venturi
and mixed once again with air from the air cleaner. This fuel/air mixture
is now of optimum concentration and is fed into the combustion
chamber of the engine.
Choke System
The choke system provides easier starting in cold weather conditions.
When the engine is started with a closed choke, the negative pressure
applied to the main nozzle increases. This causes a larger amount of
fuel to be drawn into the carburetor, which in turn makes the engine
easier to start.
WM 130 WM 170 WM 270
A/C Type Standard Dual Standard Dual Standard Dual
Main Jet 63.8 77.5 76.3 98.0 96.0
Pilot Jet 37.5 40.0 40.0
Pilot screw turning 1-1/8 1-3/4 1-1/2
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