Stihl PH 90 Instruction Manual - Page 13

superficial cracks. Such attachments may shatter at high speed and cause serious or fatal injury. WARNING When using rigid blades, avoid cutting close to fences, sides of buildings, tree trunks, stones or other such objects that could cause the power tool to kick out or could cause damage to the blade. STIHL recommends use of the nylon line heads for such jobs. In addition, be alert to an increased possibility of ricochets in such situations. WARNING If a rotating metal blade strikes a rock or other hard object, sparks may be created, which can ignite flammable materials under certain circumstances. Flammable materials can include dry vegetation and brush, particularly when weather conditions are hot and dry. When there is a risk of fire or wildfire, do not use metal blades around flammable materials or around dry vegetation or brush. Contact your local fire authorities or the U.S. Forestry Service if you have any question about whether vegetation and weather conditions are suitable for the use of a metal blade. WARNING If the head, blade or deflector becomes clogged or stuck, always shut off the engine and make sure the cutting attachment has stopped before cleaning. Grass, weeds, etc. should be cleaned off the blade or from around the head at regular intervals. WARNING To reduce the risk of unintentional rotation of the cutting attachment and injury, always shut off the engine and remove the spark plug boot before replacing the cutting attachment. To reduce the risk of injury, always shut off the engine before adjusting the length of the nylon line on manually adjustable mowing heads. WARNING The gearbox becomes hot during operation. To reduce the risk of burn injury, do not touch the gear housing when it is hot. WARNING Never modify your muffler. Any modification could cause an increase in heat radiation, sparks or sound level, thereby increasing the risk of fire, burn injury or hearing loss. You may also permanently damage the engine. Have your muffler serviced and repaired by your STIHL servicing dealer only. WARNING The muffler and other parts of the engine (e.g. fins of the cylinder, spark plug) become hot during operation and remain hot for a while after stopping the engine. To reduce risk of burns, do not touch the muffler and other parts while they are hot. Keep the area around the muffler clean. Remove excess lubricant and all debris such as pine needles, branches or leaves. Let the engine cool down English sitting on concrete, metal, bare ground or solid wood (away from any combustible substances. WARNING An improperly mounted or damaged cylinder housing or a damaged/deformed muffler shell may interfere with the cooling process of the muffler. To reduce the risk of fire or burn injury, do not continue work with a damaged or improperly mounted cylinder housing or a damaged/deformed muffler shell. Your muffler is furnished with a spark arresting screen designed to reduce the risk of fire from the emission of hot particles. Never operate your unit with a missing or damaged spark arresting screen. If your gas/oil mix ratio is correct (i.e., not too rich), this screen will normally stay clean as a result of the heat from the muffler and need no service or maintenance. If you experience loss of performance and you suspect a clogged screen, have your muffler maintained by a STIHL servicing dealer. Some state or federal laws or regulations may require a properly maintained spark arrestor for certain uses. See the "Maintenance, Repair and Storing" section of these Safety Precautions. Remember that the risk of a brush or forest fire is greater in hot or dry conditions. FS 90, FS 90 R 11