Husqvarna K1270 Workshop Manual page 44

Carburettor
14.1. CARBURETTOR VERSIONS
The carburettor technology is being continuously
developed and refined.
The carburettor version can be read from the
marking as shown in the illustration, for example,
W69 950.
The components that are subject to service are
usually identical from version to version, such as
needle valve, pump diaphragm, measurement
chamber diaphragm etc.
14.2. FUNCTIONAL TEST
PRESSURE TESTER
The pressure tester 501 56 27-01 has a pump
piston that is operated with one hand.
The pressure tester is supplied with an adapter
nipple for small sizes. Make the hose connection to
the nipple as short as possible, this gives a clearer
test result.
LEAKING NEEDLE VALVE – INDICATIONS
A leaking needle valve can be seen in numerous
ways. A machine that is run for short periods is
often difficult to start when it is warm, fuel leaks
into the venturi and gives too much fuel for the next
warm start. With a cold start, especially when the
machine has not been used for a long period, the
fuel chamber above the needle has been slowly
emptied and fuel has evaporated. First after several
attempts to start, has new fuel been pumped
forwards and the machine starts.
NEEDLE VALVE – TESTING
Reliable inspection of the needle valve's function
demands certain conditions. The clearest result is
obtained from a carburettor that is drained of fuel,
yet still has some fuel residue. A completely "dry"
carburettor, or a carburettor that has not been used
for a long time gives a measurement result that is
difficult to interpret.
Connect a thin, short hose to the carburettor's fuel
pipe. Pump up the pressure to approximately 200
kPa and let the fuel run out through the venturi. Not
until air emerges from the venturi, can the function
of the needle valve be tested as set out below.
If the needle valve does not open at 250 kPa
(max. permitted pressure test) the needle valve
has jammed. This can usually be forced open by
blowing gently through the hole for filter compensa-
tion (A).
Test the needle valve's function as follows: Pump a
pressure to 100–250 kPa, the needle valve should
then lift. The pressure should then drop to 100–50
kPa and then drop significantly slower or stop
completely. Pressure drop after 50 kPa indicates
44
- English
CARBURETTOR - VERSIONS
CARBURETTOR - PRESSURE TESTER
A
CARBURETTOR - LEAKING NEEDLE VALVE TEST