Maintenance; General; Carburetor Adjustment; Low Speed Jet L - Husqvarna 55 EPA I Operator's Manual

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 authorised 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.
H
L
1/2
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.
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: 2500 rpm

MAINTENANCE

1/2
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. 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.
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. 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.
When test run at the factory, the high speed jet is set so that
the engine satisfies the applicable legal requirements at the
same time as achieving maximum performance. The
carburetor's high speed jet is then locked using a limiter cap
in the fully screwed out position. The limiter cap limits the
potential to adjust the high speed jet to at most half a turn.
To adjust the carburetor correctly you should contact a
mechanic with access to a rev counter.
– 29
English