Husqvarna 250 PS Workshop Manual page 21

For Husqvarna Parts Call 606-678-9623 or 606-561-4983
!
www.mymowerparts.com
Carburettor operation and adjustment
!
WARNING! Never start the pruning saw if the
hydraulic oil tank and hoses are not fitted. If the
hydraulic oil tank is not fitted the clutch may come
loose and cause injury. If the hoses are not fitted
the engine cannot be revved up and the hydraulic
pump and clutch may be damaged.
The carburettor controls engine speed via the throttle.
Fuel is mixed with air in the carburettor. The L and H
needles are used to adjust the amount of fuel that is
mixed with air when the throttle is activated. If they are
turned clockwise the fuel/air mixture is made richer
(more fuel). The T screw controls the throttle setting at
idle; turning it anticlockwise reduces the idle speed.
WARNING! Do not operate the pruning saw until it
has been correctly adjusted or repaired.
When the carburettor is correctly adjusted the pruning
saw should accelerate smoothly without hesitating and
the engine will burble slightly at full throttle. This
indicates that the pruning saw is working at maximum
efficiency.
NOTE! The chain must not rotate at idle.
Before adjusting
NOTE! Before making any adjustment make sure the air
filter is clean and that the hydraulic tank and hoses are
connected.
Place the pruning saw on a flat surface and make sure
the bar and chain are pointing away from you and cannot
touch the surface or any other object.
Gently screw the L and H needles clockwise all the way
in. Then unscrew both needles one turn. The carburettor
setting is now H=1 and L=1. Start the pruning saw and
let it run for ten minutes to warm up.
NOTE! If the chain rotates at idle, turn the T screw
clockwise until it stops.
Basic setting
Gently screw the H and L needles all the way in. Then
open H 1 1/4 turns and open L 1 turn. The basic setting
can vary between H=1 to 1 1/4 turns and L=1 to 1 1/4
turns.
NOTE! If the chain rotates at idle, turn the T screw
clockwise until it stops.
The basic setting is richer than the optimum setting and
should be maintained for the first 3-4 hours the saw is
used. The carburettor adjustment can then be fine tuned.
3
21