Maintenance; Carburettor - Husqvarna 357XP Operator's Manual

Carburettor

Your Husqvarna product has been designed and
manufactured to specifications that reduce harmful
emissions.
Function, Basic settings, Fine adjustment
WARNING! Do not start the chain saw unless
!
the bar, chain and clutch cover (chain brake)
are fitted, otherwise the clutch may come
loose and cause personal injury.
Function
• The carburettor governs the engine's speed via the
throttle control. Air and fuel are mixed in the carburettor.
The air/fuel mixture is adjustable. Correct adjustment is
essential to get the best performance from the machine.
• The setting of the carburettor means that the engine is
adepted to local conditions, for example, the climate,
altitude, fuel and the type of 2-stroke oil.
• The carburettor has three adjustment controls:
- L = Low speed jet
- H = High speed jet
- T = Idle adjustment screw
L
T
• The L and H-jets are used to adjust the supply of fuel to
match the rate that air is admitted, which is controlled with
the throttle. If they are screwed clockwise the air/fuel ratio
becomes leaner (less fuel) and if they are turned anti-
clockwise the ratio becomes richer (more fuel). A lean
mixture gives a higher engine speed and a rich mixture
gives a lower engine speed.
• The T-screw regulates the throttle setting at idle speed. If
the T-screw is turned clockwise this gives a higher idle
speed; turning it anti-clockwise gives a lower idle speed.
Basic settings and running in
The carburettor is set to its basic setting when test run at the
factory. The basic setting is richer than the optimum setting
and should be maintained for the first hours that the machine
is in use. The carburettor should then be finely adjusted. Fine
adjustment should be carried out by a suitably trained person.
CAUTION! If the chain rotates while idling the T-screw
must be turned anti-clockwise until the chain stops.
Rec. idle speed: 2700 rpm
WARNING! Contact your servicing dealer, if
!
the idle speed setting cannot be adjusted so
that the chain stops. Do not use the chain
saw until it has been properly adjusted or
repaired.
30 –
English

MAINTENANCE

H
Fine adjustment
When the machine has been "run-in" the carburettor should
be finely adjusted. The fine adjustment should be carried
out by a qualified person. First adjust the L-jet, then the
idling screw T and then the H-jet.
Conditions
• Before any adjustments are made the air filter should be
clean and the cylinder cover fitted. Adjusting the
carburettor while a dirty air filter is in use will result in a
leaner mixture next time the filter is cleaned. This can give
rise to serious engine damage.
• Carefully turn the L and H needle to the mid point.
• Do not attempt to adjust the L and H jets beyond
either stop as this could cause damage.
• Now start the machine according to the starting
instructions and let it warm up for 10 minutes. CAUTION!
If the chain rotates while idling the T-screw must be
turned anti-clockwise until the chain stops.
• Place the machine on a flat surface so that the bar points
away from you and so that the bar and chain do not come
into contact with the surface or other objects.
Low speed jet L
Turn the low speed jet L clockwise until it stops. If the engine
accelerates poorly or idles unevenly, turn the low speed jet L
anticlockwise until good acceleration and idling are achieved.
CAUTION! If the chain rotates while idling the T-screw
must be turned anti-clockwise until the chain stops.
Final setting of the idling speed T
Adjust the idle speed with the T-screw. If it is necessary to re-
adjust, turn the T-screw clockwise while the engine is running,
until the chain starts to rotate. Then turn counter-clockwise
until the chain stops. A correctly adjusted idle speed setting
occurs when the engine runs smoothly in every position. It
should also be good margin to the rpm when the chain starts
to rotate.
WARNING! Contact your servicing dealer, if
!
the idle speed setting cannot be adjusted so
that the chain stops. Do not use the chain
saw until it has been properly adjusted or
repaired.
High speed jet H
The high speed needle H influence the power of the machine.
A too lean adjusted high speed (high speed needle H turn too
much clockwise) gives overrevs and damages the engine. Do
not allow the engine to run at full speed for more than 10
seconds. Turn the high speed needle H counter-
clockwiseuntil the stop. If the engine runs roughly, turn the
high speed needle slowly the minimum amount clockwise
until the engine runs smoothly. The high speed needle H is
correctly set when the saw "4-cycles" a little. If the machine
"whistles" the setting is too lean. If there is too much exhaust