Husqvarna 3120XP Maintenance, Carburettor, Function, Basic settings, Fine adjustment, Conditions

MAINTENANCE

Carburettor

Your Husqvarna product has been designed and manufactured to specifications that reduce harmful emissions. After the engine has used 8-10 tanks of fuel the engine will be run-in. To ensure that it continues to run at peak performance and to minimise harmful exhaust emissions after the running-in period, ask your dealer/ service workshop (who will have a rev counter at their disposal) to adjust your carburettor.

Function, Basic settings, Fine adjustment

!	WARNING! Do not start the chain saw
	unless the bar, chain and clutch cover
	(chain brake) are fitted, otherwise the
	clutch may come loose and cause
	personal injury.

Function

•The carburettor governs the engine’s speed via the throttle control. Air and fuel are mixed in the carburettor. The air/fuel mixture is adjustable. Correct adjustment is essential to get the best performance from the machine.

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

•The carburettor has two adjustment controls:

-L = Low speed jet

-T = Idle adjustment screw (Maximum speed is controlled by a fixed jet/electronic speed governor).

•The amount of fuel that is mixed with the air admitted by the throttle opening is adjusted using the low speed jet. If this is turned clockwise it gives a leaner air/fuel mixture (less fuel) and if it is turned anti-clockwise it gives a richer air/fuel mixture (more fuel). A leaner mixture gives a higher engine speed, while a richer mixture gives a lower engine speed.

•The T-screw regulates the throttle setting at idle speed. If the T-screw is turned clockwise this gives a higher idle speed; turning it anti-clockwise gives a lower idle speed.

Basic settings and running in

The basic carburettor settings are adjusted during testing at the factory. The basic setting is: L = 1 turn.

Fine adjustment

When the saw has been ”run-in” the carburettor should be finely adjusted. The fine adjustment should be carried out by qualified person. The L-needle is adjusted first, then the idling screw T.

The recommended engine speeds are as follows: Idle speed 2500 rpm

Changing the type of fuel

Fine tuning may be required if the chain saw, after changing the type of fuel, performs differently with regard to starting, acceleration, maximum speed, etc.

Conditions

•Before any adjustments are made the air filter should be clean and the cylinder cover fitted. Adjusting the carburettor while a dirty air filter is in use will result in a leaner mixture next time the filter is cleaned. This can give rise to serious engine damage.

•Turn the low speed jet carefully clockwise until it bottoms. Now turn it one turn anti-clockwise. The carburettor is now set to L = 1.

•Now start the machine according to the starting instructions and let it warm up for 10 minutes.

CAUTION! If the chain rotates while idling the T- screw must be turned anti-clockwise until the chain stops.

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

Low speed jet L

Try to find the highest idle speed by turning the low speed jet L clockwise then anti-clockwise. When the highest speed has been found, turn the low speed jet L 1/4 turn anti-clockwise.

CAUTION! If the chain rotates while idling the T-screw must be turned anti-clockwise until the chain stops.

Fine adjustment of the idle speed T

Adjust the idle speed with the T-screw. If it is necessary to re-adjust, turn the T-screw clockwise while the engine is running, until the chain starts to rotate. Then turn anti- clockwise until the chain stops. When the idle speed is correctly adjusted the engine should run smoothly in every position and the engine speed should be safely below the speed at which the chain starts to rotate.

!	WARNING! Contact your servicing
	dealer, if the idle speed setting cannot be
	adjusted so that the chain stops. Do not
	use the chain saw until it has been
	properly adjusted or repaired.

English – 29