Carburetor - Husqvarna 455 Rancher II Workshop Manual

7.14 Carburetor

WARNING!
The fuel used in the chain saw has
the following hazardous proper-
ties:
1. The fluid and its vapor are toxic.
2. Can cause skin irritation.
3. Is highly flammable.
Description
The figures accompanying this description do not
correspond with the carburetor on the chain saw.
They only represent the design and function.
Design
The carburetor is based on three sub-systems:
• Metering unit, A.
• Mixing unit, B.
• Pump unit, C.
The needles and the fuel's control functions are
located in the metering unit (A). Here the correct
quantity of fuel is adjusted for the actual speed and
power output. See figure 27.
The mixing venturi (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 28.
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. See figure 29.
Fig 27
Fig 28
Fig 29
Repair Instructions
B
35
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