Carburettor - Husqvarna 555 XP Workshop Manual

Repair Instructions

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:
• 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 unit B 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 28.
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 29.
34
- English
Fig 27
Fig 28
Fig 29
B