Maintenance; Carburetor - Husqvarna 343F Manuel D'utilisation

Carburetor

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.
WARNING! The complete clutch cover and
!
shaft must be fitted before the machine is
started, otherwise the clutch can come
loose and cause personal injury.
Carburetor adjustment
The carburettor can be designed in different ways, depending
on the existing environmental and emissions legislation. Some
machines are equipped with movement limiters on the
carburettor's adjuster screws. These limit the adjustment range
to a maximum of 1/2 turn.
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.
64 – English

MAINTENANCE

1/2
1/2
• 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.
Rec. idle speed: See the Technical data section.
Recommended max. speed: See the Technical data section.
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.
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, make sure that the air
filter is clean and the air filter cover is fitted. If you adjust the
carburettor when the air filter is dirty it will result in a leaner
mixture when the filter is finally cleaned. This can lead to
serious engine damage.
• Carefully turn both jets, L and H, so that they are midway
between fully screwed in and fully screwed out.
• 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 cutting attachment rotates when the
engine is idling the idle adjustment screw T should be
turned anti-clockwise until the cutting attachment stops.
Low speed jet L
Try to find the highest idling speed, turning the low speed
needle L clockwise respectively counter-clockwise. When the
highest speed has been found, turn the low speed needle L 1/
4 turn counter-clockwise.
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.