Husqvarna 390 XP Owners Manual - Page 31

MAINTENANCE • The carburettor has three adjustment controls: - L = Low speed jet - H = High speed jet - T = Idle adjustment screw T H L • 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. + 1/4 • 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 settings are H = 1 turn and L = 1 turn. To provide the engine's components with good initial lubrication (during running in) the carburettor should be set for a richer fuel mixture for the first 3-4 hours that the chain saw is in use. To do this, adjust the fast idle speed to 600-700 rpm below the recommended maximum fast idle speed. If you are unable to check the fast idle speed using a tachometer the H-jet should not be set for a leaner mixture than given in the basic settings. The recommended maximum fast idle speed must not be exceeded. CAUTION! If the chain rotates while idling the T-screw must be turned anti-clockwise until the chain stops. Fine adjustment When the machine has been "run-in" the carburettor should be finely adjusted. The fine adjustment should be carried out by a qualified person. First adjust the L-jet, then the idling screw T and then the H-jet. The recommended engine speeds are as follows: Max. fast idle speed, rpm Idle speed, rpm 385XP/XPG 12500 2700 390XP/XPG 13500 2700 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. • Carefully turn the L and H-jets clockwise as far as they will go. Now turn the jets one turn anti-clockwise. The carburettor is now set to H = 1 and 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 Tscrew must be turned anti-clockwise until the chain stops. L 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 using the idle adjustment screw T, if it is necessary to readjust. First turn the idle adjustment screw T clockwise until the cutting attachment starts to rotate. Then turn the screw anticlockwise until the cutting attachment stops. The idle speed is correctly adjusted when the engine will run smoothly in every position. The idle speed should also be well below the speed at which the cutting attachment 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. High speed jet H • The high speed jet H influences the power and engine speed of the machine. If the high speed jet is set too rich (H-jet screwed in too far) the machine will over-rev and this will damage the engine. Run the machine at full throttle for about 10 seconds. Then turn the H-jet 1/4 turn anti-clockwise. Run the machine at full throttle for another 10 seconds or so and listen to the difference in the fast idle speed. Repeat this procedure with the H-jet turned a further 1/4 turn anticlockwise. H English - 31