Stihl BG 86 Product Instruction Manual - Page 21

N Check the air filter and clean it if necessary. N Warm up the engine. At high altitude N Turn high speed screw (H) clockwise (leaner) - no further than stop. At sea level N Turn high speed screw (H) slightly counterclockwise (richer) - no further than stop. Adjusting Idle Speed N Turn the low speed screw (L) slowly clockwise until the engine runs and accelerates smoothly. If acceleration is good, the idle setting is too lean: N Turn the low speed screw (L) slowly counterclockwise until the engine runs and accelerates smoothly. English Checking the Spark Plug It is usually necessary to change the setting of the idle speed screw (LA) after every correction to the low speed screw (L). Engine stops while idling N Check the standard setting. N Turn the idle speed screw (LA) clockwise until the engine runs smoothly. Erratic idling behavior If acceleration is poor even though the standard setting is correct, the idle setting is too rich: 295BA077 KN 000BA002 KN 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. If engine is down on power, difficult to start or runs poorly at idling speed, first check the spark plug. N Remove spark plug as described in chapter "Starting / Stopping the Engine". N Clean dirty spark plug. N Check the electrode gap (A) and readjust if necessary - see "Specifications". N Use only resistor type spark plugs of the approved range. BG 56, BG 56 C, BG 66, BG 86, BG 86 C, SH 56, SH 56 C, SH 86, SH 86 C 19