Stihl MS 193 C-E Product Instruction Manual - Page 43

N Turn the low speed screw (L) counterclockwise, no further than stop, until the engine runs and accelerates smoothly. It is usually necessary to change the setting of the idle speed screw (LA) after every correction to the low speed screw (L). Fine Tuning for Operation at High Altitude A slight correction of the setting may be necessary if engine does not run satisfactorily: N Carry out the standard setting. N Warm up the engine. N Turn high speed screw (H) slightly clockwise (leaner) - no further than stop. NOTICE After returning from high altitude, reset the carburetor to the standard setting. If the setting is too lean there is a risk of engine damage due to insufficient lubrication and overheating. Spark Arresting Screen in Muffler N If the engine is down on power, check the spark arresting screen in the muffler. N Wait for the muffler to cool down. N Remove the sprocket cover. 2 3 1 N Take out the screw (1). N Remove the baffle plate (2). N Remove the spark arresting screen (3). 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 Fit the baffle plate. 467BA020 KN 418BA009 KN English 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 Insert a suitable tool in the side of the spark plug boot. N Pry off the spark plug boot. N Unscrew the spark plug. MS 193 C 41