Husqvarna 250PS manual Maintenance, Carburettor

MAINTENANCE

Carburettor

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

After your unit has been run 8-10 tanks of fuel the engine has broken in. To ensure that your unit is at peak performance and producing the least amount of harmful emissions after break in, have your authorized servicing dealer, who has a revolution counter at his disposal, to adjust your carburettor for optimum operating conditions.

!WARNING!

Do not start the engine without the hydraulic tank and hoses connected. If you do, the clutch might come loose and cause severe injuries.

Functioning		L	H
•	The carburettor governs
	the engine speed via the
	throttle trigger. In the
	carburettor, air/fuel is
	mixed. This air/fuel
	mixture is adjustable. If
	you want to take advan-
	tage of the maximum
	power output of the
	engine, the setting must be
	correct.
•	The setting of the		T
	carburettor means that the
	engine is adjusted to local
	conditions, for example
	climate, altitude, petrol
	and type of two-stroke oil.

•The carburettor has three adjustment possibilities: L = Low speed needle

H = High speed needle

T = Idle speed adjustment screw

•The fuel quantity required in proportion to the airflow the throttle trigger position allows is adjusted by means of the L- and H-needles. Turning the needles clockwise gives a leaner fuel mixture (less fuel), turning them counter- clockwise gives a richer fuel mixture (more fuel). A lean mixture gives higher rpms and a rich one lower rpms.

•The idling speed screw (T) regulates the position of the throttle lever in the idling speed position. Turning the idling speed screw clockwise gives a higher idling speed, turning it counter-clockwise gives a lower idling speed.

Basic setting

The carburettor is adjusted to a basic setting at the factory. The basic setting is richer than the optimum setting and shall be maintained during the first working hours. The carburettor should be fine adjusted. The basic setting can be varied between H = 1 to 1 1/4 turns and L = 1 1/4 turns.

NOTE!

If the chain rotated during idling the T-screw should be turned anti-clockwise until the chain stops.

Fine adjustment

•When the tree pruner is ”run in” the carburettor should be fine adjusted. Fine adjustment should be carried out by trained personnel. The L-nozzle is adjusted first, then the H-nozzle and finally the idling screw T. The following revs recommendations are applicable:

Max. race revs	= 11 000, rpm
Idling revs	= 2 500, rpm

Prerequisites

•During all adjustment the air filter should be clean and the cylinder casing fitted.

•Carefully screw in (clockwise) the L- and H-nozzles to the bottom.

Then unscrew (anti-clockwise) the nozzles 1 turn. The carburettor now has the setting H = 1 and L = 1.

•Start the pruner as per the starting instructions and run for about 10 minutes until it is warm.

NOTE!

If the chain rotates during idling the T-screw should be turned anti-clockwise until the chain stops.

•Place the pruner on a flat surface so that the blade is pointing away from you and not in contact with the surface or any other object.

Low speed nozzle L

Search for the highest idling revs by means of slowly screwing the low speed nozzle clockwise or anti-clockwise. When the highest revs have been found screw the L-nozzle anti- clockwise 1/4 turn.

NOTE!

If the chain rotates during idling the T-screw should be turned anti-clockwise until the chain stops.

High speed nozzle H

The high speed nozzle H affects the engine output and revs. A lean mixture of the high speed nozzle (H-nozzle screwed in too far) gives over-revs resulting in damage to the engine. Run the engine at full throttle for about 10 seconds.

The H-nozzle is correctly adjusted when the saw putters slightly. If there is excessive smoke from the exhaust while the pruner is puttering excessively the setting is too rich. Turn the H-nozzle clockwise until the setting sounds right.

NOTE!

To obtain an optimal setting contact a professional with access to a tachometer.

Fine adjustment of idling T

The setting of the idling speed is done with the screw marked T. If adjustment is necessary screw in (clockwise) the idling screw T with the engine running until the chain starts to rotate. Then open (anti-clockwise) until the chain stands still. The correct setting of the idling revs is obtained when the engine works regularly in all positions with a good margin until the revs when the chain begins to rotate.

!WARNING!

Contact your servicing dealer, if the idle speed setting cannot be adjusted. Do not use the pruner until it has been properly adjusted or repaired.

20 – English