Stihl MS 291 Product Instruction Manual - Page 44

5902BA014 KN English Spark Arresting Screen in Muffler In some countries the muffler is equipped with a spark arresting screen. N If the engine is down on power, check the spark arresting screen in the muffler. N Wait for the muffler to cool down. 1 2 N Take out the screw (1). N Pull out the spark arresting screen (2). N Clean the spark arresting screen. If the screen is damaged or heavily carbonized, fit a new one. N Refit the spark arresting screen. N Insert the screw and tighten it down. 0001BA009 KN Spark Plug If engine is down on power, difficult to start or runs poorly at idling speed, first check the spark plug. Fit a new spark plug after approx. 100 operating hours or earlier if the electrodes are badly eroded. Wrong fuel mix (too much engine oil in the gasoline), a dirty air filter and unfavorable running conditions (mostly at part throttle etc.) affect the condition of the spark plug. These factors cause deposits to form on the insulator nose which may result in trouble in operation. Removing the spark plug N Remove the shroud - see "Shroud". N Move the Master Control lever to the stop position (0). N Pull off the spark plug boot. N Clean away loose dirt from around the spark plug. 5902BA013 KN 1 N Insert the combination wrench through the grommet (1) and turn it as necessary to engage the spark plug's hexagon. N Push the combination fully home against the cylinder. N Unscrew the spark plug. Checking the Spark Plug A N Clean dirty spark plug. N Check electrode gap (A) and readjust if necessary - see "Specifications". N Use only resistor type spark plugs of the approved range. Rectify problems which have caused fouling of spark plug: 000BA039 KN 42 MS 271, MS 291, MS 291 C