Husqvarna 340 Workshop Manual page 38

Basic requirements
• Before making any adjustments the air filter
should be clean and the cylinder cover should
be in place. If the carburettor is adjusted with a
dirty air filter, the mixture will be too weak next
time the air filter is cleaned. This can cause
serious engine damage.
• Carefully screw in the L and H jets fully, then
back them off 1 turn. The carburettor now has
the settings H = 1 and L = 1.
• Start the chainsaw and allow it to warm up for 10
minutes.
• Place the saw on a flat surface so that the guide
bar is pointing away from you and the guide bar
and chain are not touching the surface.
Low speed jet L
• Find the highest idling speed by slowly screwing
the L screw in and then out again.
• When the highest speed has been found, screw
out the L screw 1/8 - 1/4 turn.
Fine adjustment of idling speed T
• The idling speed is adjusted using the screw
marked T.
• If adjustment is necessary, screw in the idling
screw T until the chain starts to turn. Then screw
it out until the chain stops moving.
• The idling speed is correctly set when the
engine runs smoothly in all positions and there
is a clear margin to the speed at which the chain
starts to move.
High speed jet H
• The high speed jet H influences the saw power
output and engine speed. If the H jet is set too
weak the saw will over-rev, which could cause
engine damage.
• Run the saw at full throttle for about 10 seconds.
H=1.
• Then screw out the H screw 1/4 turn. H=1 1/4.
• Run the saw again at full throttle for about 10
seconds and listen to the difference in the engine
note. Repeat this procedure again with the H
screw screwed out another 1/4 turn. H=1 1/2.
• You have now run the saw at settings H ± 0, H =
+1/4 and H = +1/2 from the factory setting. At full
throttle the engine will sound different at each
setting.
• The H screw is correctly adjusted when the saw
"burbles" a little at full throttle without any load.
• If there is a lot of smoke from the silencer and
the saw does not run smoothly then the setting
is too rich.
• Screw in the H screw to the setting that sounds
right.
NOTE!
For optimum adjustment, a tachometer
should be used. The recommended
maximum speed should not be exceeded.
Carburettor – correct adjustment
• When the carburettor is correctly adjusted the
saw should accelerate without hesitation and the
engine will burble a little at full throttle without
any load.
• The chain must not turn when idling.
• If the L screw is set too weak this can make the
saw difficult to start and cause poor accelera-
tion.
• If the H screw is set too weak the saw will
produce less power, poor acceleration and there
is a risk of engine damage.
• If either the L or H screws are set too rich it will
cause acceleration problems or too low working
speed.
Repair instructions
37
English –