Stihl HS 87 R Product Instruction Manual - Page 21

Cutting blades run when engine is idling N Turn the idle speed screw (LA) counterclockwise until the cutting blades stop moving - then turn it another 1 1/2 turns in the same direction. WARNING If the cutting blades continue moving when the engine is idling, have your power tool checked and repaired by your servicing dealer. Erratic idling behavior, poor acceleration (despite correction to setting of LA screw). Idle setting is too lean N Rotate the low speed screw (L) about 1/4 turn counterclockwise until the engine runs and accelerates smoothly. Engine stops when unit is swung at idle speed Idle setting is too rich N Rotate the low speed screw (L) about 1/4 turn clockwise until the engine idles smoothly. It is usually necessary to change the setting of the idle speed screw (LA) after every correction to the low speed screw (L). 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. Fine Tuning for Operation at High Altitude English Spark Arresting Screen in Muffler N Check the spark arresting screen in the muffler after every 20 hours of operation, or if the engine is down on power or runs erratically at maximum speed. WARNING Wait for the engine to cool down completely before performing this work. N Take out the screws (1). N Remove the exhaust pipe (2). A slight correction of the setting may be necessary if engine does not run satisfactorily: HS 87 R, HS 87 T 19