Carburettor - Adjustment; Basic Settings And Running In - Husqvarna 340 Workshop Manual

Carburettor – adjustment
For instructions on adjusting the EPA carburettor
see appendix A.
Adjusting the carburettor involves adjusting the
engine to the local conditions e.g. climate, alti-
tude, fuel and type of two-stroke oil.
The carburettor is equipped with three adjustment
options.
L = Low speed jet
H = High speed jet
T = Idling adjustment screw
The L and H jets adjust the fuel flow to match the
airflow that the throttle valve opening allows.
Turning them clockwise makes the fuel/air mixture
weaker (less fuel in relation to the amount of air)
and turning them anti-clockwise makes the fuel/air
mixture richer. A weak mixture increases the
engine speed and a rich mixture decreases the
engine speed.
The T screw controls the throttle position when
idling. Turning the T screw clockwise gives faster
idling; turning it anti-clockwise lowers idling
speed.
WARNING!
The guide bar, chain and clutch
cover must be fitted before the
saw is started, otherwise the
clutch may fly off and cause inju-
ry.

Basic settings and running in

During testing at the factory the carburettor is
adjusted to the basic factory settings.
The factory settings are H = 1 turn and L = 1
turn.
To ensure that engine components receive
adequate lubrication (running in) the carburet-
tor should be set to a somewhat richer fuel
mixture for the chainsaw's first 3-4 running
hours. This is done by adjusting the maximum
speed to 6-700 rpm less than the recom-
mended maximum speed.
If it is not possible to check the maximum speed
with a tachometer then the H jet should not be set
to a weaker mixture than the basic factory setting.
The recommended maximum speed must not be
exceeded.
NOTE!
If the chain turns at idling speed, the T
screw should be turned anti-clockwise
until the chain stops.
Fine adjustment
Once the chainsaw is "run in" the carburettor should
be readjusted. First adjust the L jet screw, then the
idling screw T and finally the H jet screw.
The recommended engine speeds are as follows:
Model Max revs
340 12,500 rpm
345 12,500 rpm
346XP/G 14,200 rpm
350 13,000 rpm
350 EPA 13,000 rpm
351 13,000 rpm
353 13,000 rpm
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.
Repair instructions
Idle revs
2,700 rpm
2,700 rpm
2,700 rpm
2,700 rpm
2,700 rpm
2,700 rpm
2,700 rpm
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English –