Carburettor - Husqvarna T540 XP Workshop Manual

7.13 Carburettor

WARNING!
The fuel used for the chain saw
has the following characteristics:
1. The liquid and its fumes are
poisonous.
2. Can cause skin irritation.
3. Is very flammable.
Description
The images for this description do not correspond
to the carburettor on the chain saw. They purely
show the principle for the design and function.
Design
The carburettor is based on three sub-systems:
• Metering unit, A.
• Mixing unit, B.
• Pump unit, C.
The jet screws and the fuel's control functions are
located in the metering unit A. Here the correct
volume of fuel is adjusted for the actual speed and
power output. See figure 34.
The mixing unit B houses the choke, throttle valve
and 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 35.
In the pump unit C, fuel is pumped from the fuel
tank to the carburettor's metering unit. One side of
the pump diaphragm is connected to the crankcase
and pulses in time with the pressure changes in the
crankcase. The other side of the diaphragm pumps
the fuel. See figure 36.
Fig 34
Fig 35
Fig 36
Repair instructions
B
39
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