Husqvarna GR41, RS52 Maintenance, Carburettor adjustment, Function, Basic setting, Conditions

MAINTENANCE

Carburettor

Your Jonsered product has been designed and manufactured to specifications that reduce harmful exhaust fumes. The engine will be run in after it has used 8-10 tanks of fuel. To ensure that the engine runs at peak performance and produces as little harmful exhaust fumes as possible after the running-in period, ask your dealer/service workshop (which has a rev counter for this purpose) to adjust your carburettor.

WARNING! The complete clutch cover and

!shaft must be fitted before the machine is started, otherwise the clutch can come loose and cause personal injury.

Carburettor adjustment

The carburettor can be designed in different ways, depending on the existing environmental and emissions legislation. Some machines are equipped with movement limiters on the carburettor’s adjuster screws. These limit the adjustment range to a maximum of 1/2 turn.

1/2

1/2

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 three adjustment controls: L = Low speed jet

H = High speed jet

T = Idle adjustment screw

GR41/50 RS44 RS52

•The L and H-jets are used to adjust the supply of fuel to match the rate that air is admitted, which is controlled with the throttle. If they are screwed clockwise the air/fuel ratio becomes leaner (less fuel) and if they are turned anti- clockwise the ratio becomes richer (more fuel). A lean mixture gives a higher engine speed and a rich 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 setting

•The basic carburettor settings are adjusted during testing at the factory. The basic setting is richer than the optimal setting and should be maintained for the first few hours the machine is in use. The carburettor should then be finely adjusted. Fine adjustment should be carried out by a skilled technician.

The basic setting can vary between: H = 1 - 1 1/4 turns and L = 1 - 1 1/4 turns.

CAUTION! If the cutting attachment rotates when the engine is idling the idle adjustment screw T should be turned anti- clockwise until the cutting attachment stops.

Rec. idle speed: 2700 rpm

WARNING! If the idle speed cannot be

!adjusted so that the cutting attachment stops, contact your dealer/service workshop. Do not use the machine until it has been correctly adjusted or repaired.

CAUTION! The machine should only be run for short periods at its highest speed. For optimum adjustment of the carburettor, contact a qualified dealer/service workshop that has a revolution counter at their disposal.

Recommended max. speed: See the Technical data section.

During the running-in period (8-10 tanks of fuel) the maximum speed should be set 600-700 rpm below the recommended maximum speed (= open the high speed jet H a further 1/8 turn).

Conditions

•Before any adjustments are made, make sure that the air filter is clean and the air filter cover is fitted. If you adjust the carburettor when the air filter is dirty it will result in a leaner mixture when the filter is finally cleaned. This can lead to serious engine damage.

•Carefully turn both jets, L and H, so that they are midway between fully screwed in and fully screwed out.

•Do not attempt to adjust the L and H jets beyond either stop as this could cause damage.

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

CAUTION! If the cutting attachment rotates when the engine is idling the idle adjustment screw T should be turned anti- clockwise until the cutting attachment stops.

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.

+ 1/4

L

CAUTION! If the cutting attachment rotates when the engine is idling the idle adjustment screw T should be turned anti- clockwise until the cutting attachment stops.

26 – English