Husqvarna 340, 345, 346XP,350, 351, 353 Carburettor - adjustment, Basic settings and running in

Repair instructions

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	Idle revs
340	12,500 rpm	2,700 rpm
345	12,500 rpm	2,700 rpm
346XP/G	14,200 rpm	2,700 rpm
350	13,000 rpm	2,700 rpm
350 EPA	13,000 rpm	2,700 rpm
351	13,000 rpm	2,700 rpm
353	13,000 rpm	2,700 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.

English – 37