Stihl BR 550 Product Instruction Manual - Page 24

English Engine Management Adjusting the Carburetor Exhaust emissions are controlled by the design of the fundamental engine parameters and components (e.g. carburation, ignition, timing and valve or port timing) without the addition of any major hardware. Machines without adjustable carburetor On certain machine versions it is no longer necessary to adjust the carburetor. Such machines have no setting symbol on the shroud. HL With this carburetor it is only possible to adjust the high speed and low speed screws within fine limits. Standard Setting N Shutting down the engine N Check the air filter and replace it if necessary. N Check that the throttle cable is properly adjusted - readjust if necessary - see chapter on "Adjusting the Throttle Cable". N Check the spark arresting screen (country-specific) in the muffler and clean or replace if necessary. 452BA105 KN These machines have been set at the factory to provide an optimum fuel-air mixture in all locations and operating conditions. Adjusting idle speed Engine stops while idling: N Turn the idle speed screw (LA) slowly clockwise until the engine runs smoothly. Machines with adjustable carburetor The carburetor comes from the factory with a standard setting. This setting provides an optimum fuel-air mixture under most operating conditions. HL N Carefully turn both adjusting screws counterclockwise as far as stop: N The high speed screw (H) is 3/4 turn open. N The low speed screw (H) is 3/4 turn open. N Start and warm up the engine. 22 BR 500, BR 550, BR 600