Maintenance; Carburettor; Fine Adjustment - Husqvarna 3120XP Operator's Manual

Carburettor

Your Husqvarna product has been designed and
manufactured to specifications that reduce harmful
emissions. After the engine has used 8-10 tanks of fuel the
engine will be run-in. To ensure that it continues to run at peak
performance and to minimise harmful exhaust emissions
after the running-in period, ask your dealer/service workshop
(who will have a rev counter at their disposal) to adjust your
carburettor.
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.
• Adjusting the carburettor means that the engine is
adapted to local operating conditions, e.g. climate,
altitude, petrol and the type of 2-stroke oil.
• The carburettor has two adjustment controls:
- L = Low speed jet
- T = Idle adjustment screw (Maximum speed is
controlled by a fixed jet/electronic speed governor).
• The amount of fuel that is mixed with the air admitted by
the throttle opening is adjusted using the low speed jet. If
this is turned clockwise it gives a leaner air/fuel mixture
(less fuel) and if it is turned anti-clockwise it gives a richer
air/fuel mixture (more fuel). A leaner mixture gives a
higher engine speed, while a richer 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 basic carburettor settings are adjusted during testing at
the factory. The basic setting is: L = 1 turn.

Fine adjustment

When the saw has been "run-in" the carburettor should be
finely adjusted. The fine adjustment should be carried out by
qualified person. The L-needle is adjusted first, then the idling
screw T.
The recommended engine speeds are as follows: Idle
speed 2500 rpm
28 –
English

MAINTENANCE

Changing the type of fuel
Fine tuning may be required if the chain saw, after changing
the type of fuel, performs differently with regard to starting,
acceleration, maximum speed, etc.
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.
• Turn the low speed jet carefully clockwise until it bottoms.
Now turn it one turn anti-clockwise. The carburettor is now
set to L = 1.
• 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
L
Try to find the highest idle speed by turning the low speed jet
L clockwise then anti-clockwise. When the highest speed has
been found, turn the low speed jet L 1/4 turn anti-clockwise.
CAUTION! If the chain rotates while idling the T-screw
must be turned anti-clockwise until the chain stops.
Fine adjustment of the idle 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 anti-clockwise until
the chain stops. When the idle speed is correctly adjusted the
engine should run smoothly in every position and the engine
speed should be safely below the speed at which the chain
starts to rotate.
!
+ 1/4
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.