Maintenance; General; Carburettor Adjustment - Husqvarna T425 Manual De Instrucciones

General

The user must only carry out the maintenance and
service work described in this manual.
IMPORTANT! Any maintenance other than that
described in this manual must be carried out by your
servicing dealer (retailer).

Carburettor adjustment

Due to existing environmental and emissions legislation
your chain saw is equipped with movement limiters on the
carburettor adjuster screws. These limit the adjustment
possibilities to a maximum of a 1/4 turn.
Your Husqvarna product has been designed and
manufactured to specifications that reduce harmful
emissions.
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 three adjustment controls:
- L = Low speed jet
- H = High speed jet
- T = Idle adjustment screw
T
L
• 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.

MAINTENANCE

1/4
1/4
H
• 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. Avoid running at a too high speed during the
first 10 hours.
CAUTION! If the chain rotates while idling the T-screw
must be turned anti-clockwise until the chain stops.
Rec. idle speed: 2900 rpm
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.
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.
• 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.
• 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.
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.
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.
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English 29