Carburettor - Husqvarna T425 Workshop Manual

7.13 Carburettor

WARNING!
The fuel used for the chain saw
has the following characteristics:
1. The liquid and its fumes are poi-
sonous.
2. Can cause skin irritation.
3. Is very fl ammable.
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. The
carburettor is based on three sub-systems:
Metering unit
The needles and the fuel's control functions are
located in the metering unit (A). Here the correct
fuel amount is adjusted for the current speed and
power output.
Mixing venturi
The mixing venturi (B) houses the choke, throttle
valve and diffuser jets. Here, air and fuel are mixed
to create a fuel-air mix that can be ignited by the
ignition spark.
Pump unit
In the pump unit (C), fuel is pumped from the fuel
tank to the 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.
Fig 30
Fig 31
Fig 32
Repair instructions
A
B
C
35
English -