Carburettor - Husqvarna TrioBrake 550XPG Workshop Manual

7.14 Carburettor

WARNING!
The fuel used in the chain saw has
the following hazardous properties:
1. The fluid and its vapour are
poisonous.
2. Can cause skin irritation.
3. Is highly inflammable.
Description
The figures accompanying this description do not
correspond with the carburettor on the chain saw.
They show only the principle of design and func-
tion.
Design
The carburettor is based on three sub-systems:
• Pump unit, A.
• Metering unit, B.
• Mixing unit, C.
In the pump unit A, fuel is pumped from the fuel
tank to the carburettor's metering unit. One side
of the pump diaphragm is connected to the crank-
case and pulses in time with the pressure changes
in the crankcase.With the help of inlet and outlet
valve in diaphragm, the fuel is transfered through a
filter screen to the inlet needle. See figure 27.
The fuel control unit is attached to the metering
unit, B. Here the correct quantity of fuel is adjusted
for the actual speed and power output. See figure
28.
The mixing unit C houses the choke, the throttle
valve and the diffuser jets. Here air is mixed with
the fuel to give a fuel/air mixture that can be ignited
by the ignition spark. See figure 29.
Fig 27
Fig 28
Fig 29
A
B
C
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English -