Maintenance; General; Carburetor Adjustment - Husqvarna 455e Rancher Manual De Instrucciones

General

The user must only carry out the maintenance and
service work described in this manual. More extensive
work must be carried out by an authorized service
workshop.

Carburetor adjustment

Due to existing environmental and emissions legislation
your chain saw is equipped with movement limiters on the
carburetor adjuster screws. These limit the adjustment
possibilities to a maximum of a 1/2 turn.
Your Husqvarna product has been designed and
manufactured to specifications that reduce harmful
emissions.
Function
• The carburetor governs the engine's speed via the
throttle control. Air and fuel are mixed in the
carburetor. The air/fuel mixture is adjustable. Correct
adjustment is essential to get the best performance
from the machine.
• The setting of the carburetor means that the engine is
adapted to local conditions, for example, the climate,
altitude, fuel and the type of 2-stroke oil.
• The carburetor has three adjustment controls:
- L = Low speed jet
- H = High speed jet
- T = Idle adjustment screw
• 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.
32 – English

MAINTENANCE

1/2
1/2
L
H
T
Basic settings and running in
The basic carburetor settings are adjusted during testing
at the factory. Avoid running at a too high speed for
extended periods 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: 2700 rpm
Fine adjustment
When the machine has been "run-in" the carburetor
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
carburetor 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 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 at idle.
Do not use the chain saw until it has
been properly adjusted or repaired.
High speed jet H
At the factory the engine is adjusted at sea level.
When working at a high altitude or in different
weather conditions, temperatures and atmospheric
humidity, it may be necessary to make minor
adjustments to the high speed jet.
CAUTION! If the high speed jet is screwed in too far,
it may damage the piston/cylinder.
115 13 82-96 Rev.1 2009-03-26