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Fuel system
The carburettor’s design
The carburettor can be divided into three
di erent functional units: the metering
unit, the blending unit, and the pump unit.
The metering unit
The needles and the fuel control functions
are located here.
The carburettor’s design
The carburettor can be divided into three
di erent functional units: the metering unit,
the blending unit, and the pump unit.
The metering unit
The needles (A) and the fuel control fun-
ctions are located here.
The needle valve (B) and control
diaphragm (C) are vital to the carburettor’s
function.
The blending unit
Fuel and air are mixed here.
The blending unit
In this section of the carburettor fuel and
air are mixed in the proper proportions.
The choke and throttle valves are placed
here.
In the middle of the venturi (narrowest
part of the throughput) the main jet (D) is
found.
The pump unit
Pumps fuel from the tank to the
carburettor.
The pump unit
This is where the pump diaphragm (E)
that pumps fuel from the tank to the
carburettor’s measuring unit is found.
The diaphragm is a ected by pressure
variations in the engine’s crankcase via an
impulse channel (F).
If the channel is blocked, by grease or
a wrongly facing gasket, for example,
the pump unit does not function and the
engine cannot be started.
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