Carburettor - Husqvarna 525BX Workshop Manual

Repair instructions

7.14 Carburettor

1. Remove the air filter cover and blow the carbu-
rettor compartment clean with compressed air.
2. Disconnect the throttle cable from the lever arm
on the carburettor and from the guide in the
filter housing.
3. Remove carburettor screws and the fuel pipe.
4. Move the air filter housing to the side, remove
the fuel pipe 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
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
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
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.
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- English