Maintenance; Carburetor - Husqvarna 555FX Operator's Manual

Carburetor

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 setting
• The basic carburetor settings are adjusted during
testing at the factory. The basic setting is richer than
the optimal setting and should be maintained for the
first few hours the machine is in use. The carburettor
should then be finely adjusted. Fine adjustment
should be carried out by a skilled technician.
CAUTION! If the cutting attachment rotates when the
engine is idling the idle adjustment screw T should be
turned anti-clockwise until the cutting attachment stops.
Adjustment of the idle speed
Before any adjustments are made, make sure that the air
filter is clean and the air filter cover is fitted.

MAINTENANCE

Adjust the idle speed using the idle adjustment screw T, if
it is necessary to readjust. First turn the idle adjustment
screw T clockwise until the cutting attachment starts to
rotate. Then turn the screw counter clockwise until the
cutting attachment stops. The idle speed is correctly
adjusted when the engine will run smoothly in every
position. The idle speed should also be well below the
speed at which the cutting attachment starts to rotate.
Recommended idle speed: See the Technical data
section.
!
Adjusting the start throttle speed
(555RXT, 555FRM)
The correct start throttle speed is set by means of an
adjuster on the rear of the handle next to the cable. Use
this screw (5 mm Allen screw) to increase or decrease the
start throttle speed.
Proceed as follows:
1 Run the machine at idle.
2 Press the start throttle lock as described under the
heading Starting and stopping.
3 If the start throttle speed is too low (below 4000 rpm),
turn the adjuster screw A clockwise until the cutting
attachment starts to rotate. Then turn A clockwise a
further 1/2 turn.
4 If the start throttle speed is too high (above 6500 rpm),
turn the adjuster screw A anti-clockwise until the
cutting attachment stops. Then turn adjuster screw A
clockwise a further 1/2 turn.
WARNING! If the idle speed cannot be
adjusted so that the cutting attachment
stops, contact your dealer/service
workshop. Do not use the machine until
it has been correctly adjusted or
repaired.
4 mm
–
English 69