Stihl 009 Instruction Manual - Page 40

Top: Unscrewing the flat head screw Bottom: Filter cover removed The air filter's function is to hold back dust and dirt in the intake air and thus reduce wear on engine components to a minimum. 1 Dirty air filters reduce engine power, increase fuel consumption and make starting more difficult. 125BA026 LA Before removing the filter, clean loose dirt off the filter cover and the area around it to be sure that no dirt can get into the engine through the carburetor when the cover is removed. 2 Take out the M 4 flat head screw to remove the filter cover and air filter element . 125BA027 LA The intake air flows to the underside of the filter element. It follows that only the underside of the element becomes dirty. It is therefore necessary to remove the element and turn it over to check its condition. To clean the element, first knock it out on the palm of your hand and then wash it in non-flammable cleaning solution (warm soapy water) and blow out with compressed air if possible. It is best to carry a spare filter with you at all times. Refit the air filter by reversing the above sequence. When placing the filter cover in position, make sure the lugs engage in the recesses in the crankcase. Also make sure that the choke valve in the filter cover is in good condition. The element must be replaced immediately if the felt shows any signs of damage (tears, holes).