Carburettor - Husqvarna 129C Workshop Manual

7.14 Carburettor

Removing the carburettor
1
Remove the carburettor cover and blow the
carburettor compartment clean with compressed
air. Remove the air filter.
2
Disconnect the throttle cable from the lever arm on
the carburettor and from the guide in the air filter
holder.
3
Remove the tank venting hose (A) from its bracket,
the three carburettor screws (B) and the air filter
holder (C). See figure 40.
4
Remove the fuel hoses and lift off the carburettor.
The carburettor's design
The carburettor can be divided into three different
functional units: the metering unit, the blending
unit, and the pump unit.
The metering unit (figure 41)
The needles (A) and the fuel control functions are
located here.
The needle valve (B) and control diaphragm (C)
are vital to the carburettor's function.
The blending unit (figure 42)
In this section of the carburettor fuel and air are
mixed in the proper proportions.
The choke and throttle valves are placed here.
In the middle of the venturi (narrowest part of the
throughput) the main jet (D) is found.
The pump unit (figure 43)
This is where the pump diaphragm (E) that pumps
fuel from the tank to the carburettor's measuring
unit is found.
The diaphragm is affected by pressure variations in
the engine's crankcase via an impulse channel (F).
If the channel is blocked, by grease or a wrongly
facing gasket, for example, the pump unit does not
function and the engine cannot be started.
Fig 40
Fig 41
Fig 42
Fig 43
Fuel system
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