Carburettor - Husqvarna 140 Workshop Manual

7.15 Carburettor

WARNING!
The fuel used in the chainsaw has
the following hazardous properties:
1. The fluid and its fumes are
poisonous.
2. Can cause skin irritation.
3. Is highly inflammable.
Description
The drawings accompanying this description do not
correspond with the carburettor on the chainsaw.
They only show the principle for the design and
function.
Design
The carburettor is based on three sub-systems:
• The metering unit, A.
• The mixing venturi, B.
• The pump unit, C.
The jets 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 22).
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 23).
In the pump unit (C), fuel is pumped from the fuel
tank to the metering unit. One side of the pump di-
aphragm 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 24).
Fig 22
Fig 23
Fig 24
Repair instructions
33
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