Husqvarna 334T, 339XP, 338XPT, 336, Chain Saw manual Carburettor

CARBURETTOR

Carburettor

Your Husqvarna product has been designed and manufactured according to specifications that reduce harmful gases.

When you engine has consumed 8-10 tanks of fuel the engine has been "run-in". To ensure that it runs in the best possible way and emits as few harmful gases as possible after the running in period, let your dealer/service workshop that has a tachometer, adjust your carburettor so that it gives optimal performance.

Function, Basic setting, Fine tuning

WARNING! The bar, chain and clutch cover (chain brake) must be fitted before the saw is started otherwise the clutch can work loose and cause personal injury.

Function

•The carburettor controls the speed of the engine via the throttle. Air/fuel is mixed in the carburettor. This air/fuel mixture is adjustable. The adjustment must be correct to utilise the saw’s maximum power.

•Adjustment of the carburettor means that the engine is adapted to local conditions, e.g. the climate, altitude, petrol and the type of 2-stroke oil.

Conditions

•The air filter should be clean and the carburettor cover fitted when adjustments are made. Adjusting the carburettor with a dirty air filter will give a too lean fuel mixture the next time the air filter is cleaned. This can result in serious damage to the engine.

•Carefully turn the L and H-needles to the centre position between fully screwed in and fully screwed out.

•Do not attempt to adjust the needles past the stop, as this can result in damage.

•Start the saw according to the start instruction and run warm for 10 minutes.

NOTE! If the chain rotates while idling the T-screw should be turned anticlockwise until it stops.

•Place the saw on a flat surface so that the bar points away from you and so that the chain and bar do not make contact with the surface or any other objects.

Low speed needle L

Screw the L-needle clockwise until it stops. If the engine has bad acceleration or uneven idling turn the L-needle anti- clockwise until good acceleration and idling are obtained.

NOTE! If the chain rotates while idling the T-screw should be turned anticlockwise until it stops.

Fine tuning idling T

Adjustment of the idling speed is done with the screw marked T.

•The carburettor is fitted with three adjustment possibilities:

L = Low speed needle H = High speed needle

T = Adjuster screw for idling

H	L
	T

If adjustment is necessary, screw in (clockwise) the idling screw T with the engine running until the chain starts to rotate. Now open (anticlockwise) until the chain is at a standstill. A correctly set idling speed is when the engine runs smoothly in all positions with a good margin to the speed when the chain starts to rotate.

WARNING! Contact your service workshop if the idling speed cannot be adjusted so that the chain does not rotate. Do not use the saw until it is adjusted correctly or repaired.

•The fuel quantity in relation to the air flow permitted by the throttle opening is adjusted by the L and H-needles. Turning the needles clockwise gives a leaner fuel mixture (less fuel) and turning them anticlockwise gives a richer fuel mixture (more fuel). A lean mixture gives a higher speed while a richer mixture gives a lower speed.

•The T-screw regulates the position of the throttle while the engine is idling. Turning the screw clockwise gives a higher idling speed while turning it anticlockwise gives a lower idling speed.

Basic setting and running-in

The carburettor is set to its basic setting when test run at the factory. The basic setting is richer than the optimal setting and should be kept during the engine’s first working hours. Thereaf- ter the carburettor should be fine tuned. Fine tuning should be done by a qualified mechanic.

NOTE! If the chain rotates while idling the T-screw should be turned anticlockwise until it stops.

Recommended idling speed: 2,800 rpm

WARNING! Contact your service workshop if the idling speed cannot be adjusted so that the chain does not rotate. Do not use the saw until it is adjusted correctly or repaired.

Fine adjustment

•Fine adjustment of the carburettor should be carried out once the engine has been "run-in". Fine tuning should be done by a qualified mechanic. First adjust the L-needle, then the idling speed's T-screw and finally the H-needle.

High speed needle H

The high speed needle H affects the saw's power and speed. A too lean high speed needle setting (H-needle screwed in too far) gives over revving on the saw resulting in damage to the engine. Turn the H-needle anticlockwise until it stops. If the engine runs

unevenly turn the H-needleH clockwise until the engine xruns evenly.

The H-needle is set correctly when the saw "splatters" a little. If the saw "screams" the setting is too lean. If the muffler smokes heavily, at the same time as the saw splatters a great deal the setting is too rich. Turn the H-needle clockwise until you find the setting that sounds right.

NOTE! Use a mechanic with access to a tachometer to make an optimal setting.

Correctly adjusted carburettor

A correctly adjusted carburettor means that the saw accelerates without hesitation and that it 4-strokes a little at full throttle. In addition the chain should not rotate when idling. An L-needle adjusted too lean can cause starting difficulties and bad accel- eration. An H-needle adjusted too lean gives the saw lower power = "less strength", bad acceleration and/or damage to the engine. A too rich setting of the L and H-needles gives accel- eration problems or a too low working speed.

40 – English