Husqvarna K1270 Workshop Manual page 45

a leaking needle valve, or a leaking carburettor.
Check that the screws on the pump and measure-
ment chamber covers are tightened.
Testing can also be performed with the carburettor
assembled on the machine. Drain the fuel from the
carburettor by pressurising this repeatedly before
the measurement values are read.
WATER BATH
By lowering the carburettor into the water any
external leakage can be examined at the same
time as the function of the needle valve. Let the
carburettor remain in the water for as shorter time
as possible.
Connect the pressure tester to the fuel pipe. Pump
up a pressure to 50–100 kPa and observe if air
bubbles come from the carburettor.
PUMP DIAPHRAGM
Connect the pressure tester to the fuel pipe. Place
the carburettor in the water bath and pump up the
pressure to a maximum of 250 kPa. The pump
diaphragm leaks if air comes out of the impulse
duct (A).
MEASUREMENT CHAMBER DIAPHRAGM
The condition of the diaphragm cannot be checked
by pressure measurement.
A punctured diaphragm results in air being sucked
into the nozzle in the venturi instead of fuel.
MEASUREMENT CHAMBER
Note the interrelated positions of the components
when dismantling, as they can be reassembled in
the wrong order.
MEASUREMENT CHAMBER – FUNCTION
The measurement chamber has two chambers:
The air chamber (towards the cover) and the fuel
chamber (towards the carburettor body). These are
separated by the measuring chamber diaphragm.
The diaphragm controls and maintains a constant
fuel level in the fuel chamber through the mechani-
cally connected needle valve.
The air chamber is connected with the inlet, after
the air filter, and gives the air chamber the same
pressure (SmartCarb™ filter compensation).
WATER BATH
PUMP DIAPHRAGM
MEASUREMENT CHAMBER EXPLODED VIEW
MEASUREMENT CHAMBER FUNCTION
Carburettor
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