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Stihl Fs 90 R Manual

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    STIHL FS 90
    Read Instruction Manual thoroughly 
    before use and follow all safety 
    precautions – improper use can 
    cause serious or fatal injury.
    Antes de usar la máquina lea y siga 
    todas las precauciones de 
    seguridad dadas en el manual de 
    instrucciones – el uso incorrecto 
    puede causar lesiones graves o 
    							Instruction Manual
    1 - 53
    Manual de instrucciones
    54 - 111 
    							Original Instruction Manual Printed on chlorine-free paper
    Printing inks contain vegetable oils, paper can be recycled. © ANDREAS STIHL AG & Co. KG, 2016
    0458-260-8621-D. VA0.L15. 
    FS 90, FS 90 R
    {This instruction manual is protected by copyright. All rights reserved, especially the rights to reproduce, translate and process 
    with electronic systems.
    Allow only persons who fully understand 
    this manual to operate your trimmer / 
    To receive maximum performance and 
    satisfaction from your STIHL trimmer / 
    brushcutter, it is important that you read, 
    understand and follow the safety 
    precautions and the operating and 
    maintenance instructions in chapter 
    "Safety Precautions and Working 
    Techniques" before using your trimmer / 
    brushcutter. For further information you 
    can go to www.stihlusa.com.
    Contact your STIHL dealer or the STIHL 
    distributor for your area if you do not 
    understand any of the instructions in this 
    Because a trimmer / brushcutter is a 
    high-speed cutting tool some special 
    safety precautions must be observed to 
    reduce the risk of personal injury. 
    Careless or improper use may cause 
    serious or even fatal injury.
    Make sure your unit is equipped with the 
    proper deflector, handle and harness for 
    the type of cutting attachment being 
    used. Always wear proper eye 
    protection. Guide to Using this Manual 2
    Safety Precautions and Working 
    Techniques 3
    Approved Combinations of Cutting 
    Attachment, Deflector, Handle and 
    Harness 17
    Approved Power Tool Attachments 19
    Mounting the Bike Handle 19
    Mounting the Loop Handle 21
    Adjusting the Throttle Cable 23
    Fitting the Carrying Ring 23
    Mounting the Deflector 23
    Mounting the Cutting Attachment 24
    Fuel 27
    Fueling 28
    Fitting the Harness 29
    Balancing the Machine 30
    Starting / Stopping the Engine 31
    Transporting the Unit 33
    Operating Instructions 35
    Cleaning the Air Filter 35
    Engine Management 36
    Adjusting the Carburetor 36
    Spark Arresting Screen in Muffler 36
    Spark Plug 37
    Engine Running Behavior 38
    Lubricating the Gearbox 38
    Storing the Machine 39
    Sharpening Metal Cutting Blades 39
    Maintaining the Mowing Head 40
    Inspections and Maintenance by 
    Dealer 41Maintenance and Care 42
    Main Parts 44
    Specifications 46
    Maintenance and Repairs 47
    Disposal 48
    STIHL Incorporated Federal 
    Emission Control Warranty 
    Statement 48
    STIHL Incorporated California 
    Exhaust and Evaporative 
    Emissions Control Warranty 
    Statement 50
    Trademarks 52 
    							FS 90, FS 90 R
    The meanings of the pictograms 
    attached to or embossed on the 
    machine are explained in this manual.
    Depending on the model concerned, the 
    following pictograms may be on your 
    Symbols in Text
    Many operating and safety instructions 
    are supported by illustrations.
    The individual steps or procedures 
    described in the manual may be marked 
    in different ways:
    NA bullet marks a step or procedure.
    A description of a step or procedure that 
    refers directly to an illustration may 
    contain item numbers that appear in the 
    illustration. Example:
    NLoosen the screw (1).
    NLever (2) ...
    In addition to the operating instructions, 
    this manual may contain paragraphs 
    that require your special attention. Such 
    paragraphs are marked with the 
    symbols and signal words described 
    Indicates an imminent risk of severe or 
    fatal injury.
    Indicates a hazardous situation which, if 
    not avoided, could result in severe or 
    fatal injury.
    Indicates a risk of property damage, 
    including damage to the machine or its 
    individual components.
    Engineering Improvements
    STIHL’s philosophy is to continually 
    improve all of its products. As a result, 
    engineering changes and improvements 
    are made from time to time. Therefore, 
    some changes, modifications and 
    improvements may not be covered in 
    this manual. If the operating 
    characteristics or the appearance of 
    your machine differs from those 
    described in this manual, please contact 
    your STIHL dealer or the STIHL 
    distributor for your area for assistance.Guide to Using this Manual
    Fuel tank for gasoline 
    and engine oil mixture
    Press to operate decom-
    pression valve
    Manual fuel pump
    Press to operate manual 
    fuel pump
    Filler hole for gear 
    Air intake summer mode
    Air intake winter mode
    Handle heating 
    							FS 90, FS 90 R
    3 The terminology utilized in this manual 
    when referring to the power tool reflects 
    the fact that different types of cutting 
    attachments may be mounted on it. The 
    term "trimmer" is used to designate an 
    FS unit that is equipped with a nylon line 
    head or a head with flexible plastic 
    blades (i.e., the PolyCut head). A 
    "brushcutter" designates a unit 
    equipped with a rigid metal blade. Many 
    FS models may be used as either a 
    trimmer or a brushcutter – therefore, the 
    power tool is referred in this manual as a 
    "trimmer / brushcutter." Some smaller 
    and / or lightweight FS models may only 
    be used as a trimmer, i.e., they may not 
    be used with metal blades.The term "clearing saw" indicates a 
    high-powered trimmer / brushcutter that 
    is particularly suited for use with a 
    circular saw blade to clear saplings or 
    small trees.
    FS models with an "R" on the nameplate 
    were originally configured (at the time of 
    distribution) as a trimmer with a loop 
    As more fully explained later in these 
    Safety Precautions, to reduce the risk of 
    personal injury, make sure your unit is 
    equipped with the proper handle, 
    harness and deflector for the type of 
    cutting attachment you are using. Use 
    only cutting attachments that are 
    specifically authorized by STIHL for use 
    on your FS model.
    Have your STIHL dealer show you how 
    to operate your power tool. Observe all 
    applicable local safety regulations, 
    standards and ordinances.
    Do not lend or rent your power tool 
    without the instruction manual. Be sure 
    that anyone using it understands the 
    information contained in this manual.
    The use of this machine may be 
    hazardous. If the rotating line or blade 
    comes in contact with your body, it will 
    cut you. When it comes in contact with 
    solid foreign objects such as rocks or 
    bits of metal, it may fling them directly or 
    by ricochet in the direction of bystanders 
    or the operator. Striking such objects 
    could damage the cutting attachment and may cause blades to crack, chip or 
    break. Thrown objects, including broken 
    heads or blades, may result in serious or 
    fatal injury to the operator or bystanders. 
    STIHL does not recommend the use of 
    rigid blades when cutting in stony areas.
    Use your trimmer / brushcutter equipped 
    with the appropriate cutting attachment 
    only for cutting grass, brush, wood and 
    similar material.
    Do not use it for other purposes, since 
    misuse may result in personal injury or 
    property damage, including damage to 
    the machine.
    Minors should never be allowed to use 
    this power tool. Bystanders, especially 
    children, and animals should not be 
    allowed in the area where it is in use.
    To reduce the risk of injury to bystanders 
    and damage to property, never let your 
    power tool run unattended. When it is 
    not in use (e.g. during a work break), 
    shut it off and make sure that 
    unauthorized persons do not use it.
    Most of these safety precautions and 
    warnings apply to the use of all STIHL 
    trimmers / brushcutters. Different 
    models may have different parts and 
    controls. See the appropriate section of 
    your instruction manual for a description 
    of the controls and the function of the 
    parts of your model.
    Safety Precautions and 
    Working Techniques
    Because a trimmer / 
    brushcutter is a high-
    speed, fast-cutting power 
    tool sometimes equipped 
    with sharp cutting blades, 
    special safety precau-
    tions must be observed to 
    reduce the risk of per-
    sonal injury.
    It is important that you 
    read, fully understand 
    and observe the following 
    safety precautions and 
    warnings. Read the 
    instruction manual and 
    the safety precautions 
    periodically. Careless or 
    improper use may cause 
    serious or fatal injury. 
    							FS 90, FS 90 R
    4 Safe use of a trimmer / brushcutter 
    1.the operator
    2.the power tool
    3.the use of the power tool.
    Physical Condition
    You must be in good physical condition 
    and mental health and not under the 
    influence of any substance (drugs, 
    alcohol, etc.) which might impair vision, 
    dexterity or judgment. Do not operate 
    this machine when you are fatigued.
    Be alert – if you get tired, take a break. 
    Tiredness may result in loss of control. 
    Working with any power tool can be 
    strenuous. If you have any condition that 
    might be aggravated by strenuous work, 
    check with your doctor before operating 
    this machine.
    Prolonged use of a power tool (or other 
    machines) exposing the operator to 
    vibrations may produce whitefinger 
    disease (Raynaud's phenomenon) or 
    carpal tunnel syndrome.
    These conditions reduce the hand's 
    ability to feel and regulate temperature, 
    produce numbness and burning 
    sensations and may cause nerve and 
    circulation damage and tissue necrosis.All factors which contribute to 
    whitefinger disease are not known, but 
    cold weather, smoking and diseases or 
    physical conditions that affect blood 
    vessels and blood transport, as well as 
    high vibration levels and long periods of 
    exposure to vibration are mentioned as 
    factors in the development of whitefinger 
    disease. In order to reduce the risk of 
    whitefinger disease and carpal tunnel 
    syndrome, please note the following:
    –Most STIHL power tools are 
    available with an anti-vibration 
    ("AV") system designed to reduce 
    the transmission of vibrations 
    created by the machine to the 
    operator's hands. An AV system is 
    recommended for those persons 
    using power tools on a regular or 
    sustained basis.
    –Wear gloves and keep your hands 
    –Keep the AV system well 
    maintained. A power tool with loose 
    components or with damaged or 
    worn AV elements will tend to have 
    higher vibration levels.
    –Maintain a firm grip at all times, but 
    do not squeeze the handles with 
    constant, excessive pressure. Take 
    frequent breaks.
    All the above-mentioned precautions do 
    not guarantee that you will not sustain 
    whitefinger disease or carpal tunnel 
    syndrome. Therefore, continual and 
    regular users should closely monitor the 
    condition of their hands and fingers. If 
    any of the above symptoms appear, 
    seek medical advice immediately.
    The ignition system of the STIHL unit 
    produces an electromagnetic field of a 
    very low intensity. This field may 
    interfere with some pacemakers. To 
    reduce the risk of serious or fatal injury, 
    persons with a pacemaker should 
    consult their physician and the 
    pacemaker manufacturer before 
    operating this tool.
    Proper Clothing
    To reduce the risk of injury, the operator 
    should wear proper protective apparel.
    The deflector provided with your power 
    tool will not protect the operator from all 
    foreign objects (gravel, glass, wire, etc.) 
    thrown back by the rotating cutting 
    attachment. Thrown objects may also 
    ricochet and strike the operator. 
    							FS 90, FS 90 R
    Be particularly alert and cautious when 
    wearing hearing protection because 
    your ability to hear warnings (shouts, 
    alarms, etc.) is restricted.Avoid loose-fitting jackets, scarfs, 
    neckties, jewelry, flared or cuffed pants, 
    unconfined long hair or anything that 
    could become caught on branches, 
    brush or the moving parts of the unit. 
    Secure hair so it is above shoulder level.
    For illustrations and definitions of the 
    power tool parts see the chapter on 
    "Main Parts."
    Never modify this power tool in any way. 
    Only attachments supplied by STIHL 
    and expressly approved by STIHL for 
    use with the specific STIHL model are 
    authorized. Although certain 
    unauthorized attachments are useable 
    with STIHL power tools, their use may, 
    in fact, be extremely dangerous. For the 
    cutting attachments authorized by 
    STIHL for your unit, see the chapter 
    "Approved Combinations of Cutting 
    Attachment, Deflector, Handle and 
    Harness" in the instruction manual or the 
    STIHL "Cutting Attachments, Parts & 
    Accessories" catalog.
    If this tool is subjected to unusually high 
    loads for which it was not designed (e.g. 
    heavy impact or a fall), always check 
    that it is in good condition before 
    continuing work. Check in particular that 
    the fuel system is tight (no leaks) and 
    that the controls and safety devices are 
    working properly. Do not continue 
    operating this machine if it is damaged. 
    In case of doubt, have it checked by your 
    STIHL servicing dealer.
    Transporting the Power Tool
    To reduce the risk of injury from loss of 
    control and blade or line contact, never 
    carry or transport your power tool with 
    the cutting attachment moving. To reduce the risk of 
    injury to your eyes never 
    operate your power tool 
    unless wearing goggles 
    or properly fitted protec-
    tive glasses with 
    adequate top and side 
    protection complying with 
    ANSI Z87 "+" (or your 
    applicable national stand-
    ard). To reduce the risk of 
    injury to your face STIHL 
    recommends that you 
    also wear a face shield or 
    face screen over your 
    goggles or protective 
    Wear an approved safety 
    hard hat to reduce the 
    risk of injury to your head 
    when there is a danger of 
    head injuries.
    Power tool noise may 
    damage your hearing. 
    Wear sound barriers (ear 
    plugs or ear mufflers) to 
    protect your hearing. 
    Continual and regular 
    users should have their 
    hearing checked 
    Always wear heavy duty 
    work gloves (e.g. made of 
    leather or other wear 
    resistant material) when 
    handling the machine 
    and metal blades. Heavy-
    duty, nonslip gloves 
    improve your grip and 
    help to protect your 
    Clothing must be sturdy 
    and snug-fitting, but allow 
    complete freedom of 
    movement. Wear long 
    pants made of heavy 
    material to help protect 
    your legs. Do not wear 
    shorts, sandals or go 
    Good footing is very 
    important. Wear sturdy 
    boots with nonslip soles. 
    Steel-toed safety boots 
    are recommended. 
    							FS 90, FS 90 R
    6 It may be carried only in a horizontal 
    position. Grip the shaft in a manner that 
    the machine is balanced horizontally. 
    Keep the hot muffler away from your 
    body and the cutting attachment behind 
    Always shut off the engine and make 
    sure the cutting attachment has stopped 
    before putting a trimmer / brushcutter 
    down. When transporting it in a vehicle, 
    properly secure it to prevent turnover, 
    fuel spillage and damage to the unit. 
    STIHL recommends that you keep metal 
    blades covered with the transport guard 
    (optional accessory).
    Your STIHL power tool uses an oil- 
    gasoline mixture for fuel (see the 
    chapter on "Fuel" of your instruction 
    Fueling Instructions
    To reduce the risk of serious injury from 
    burns, never attempt to refuel the unit 
    until it has been completely removed 
    from the operator.
    Fuel your power tool in well-ventilated 
    areas, outdoors. Always shut off the 
    engine and allow it to cool before 
    refueling. Gasoline vapor pressure may 
    build up inside the fuel tank depending 
    on the fuel used, the weather conditions 
    and the tank venting system.
    In order to reduce the risk of burns and 
    other personal injury from escaping gas 
    vapor and fumes, remove the fuel filler 
    cap on your power tool carefully so as to 
    allow any pressure build-up in the tank 
    to release slowly. Never remove the fuel 
    filler cap while the engine is running.Select bare ground for fueling and move 
    at least 10 feet (3 m) from the fueling 
    spot before starting the engine. Wipe off 
    any spilled fuel before starting your 
    In order to reduce the risk of fuel spillage 
    and fire from an improperly tightened 
    fuel cap, correctly position and tighten 
    the fuel cap in the fuel tank opening.
    See also the "Fueling" chapter in your 
    Instruction Manual for additional 
    389BA019 KN
    ous burn injury or 
    property damage. Use 
    extreme caution when 
    handling gasoline or fuel 
    mix. Do not smoke or 
    bring any fire or flame 
    near the fuel or the power 
    tool. Note that combus-
    tible fuel vapor may 
    escape from the fuel 
    Check for fuel leakage 
    while refueling and during 
    operation. If fuel leakage 
    is found, do not start or 
    run the engine until the 
    leak is fixed and any 
    spilled fuel has been 
    wiped away. Take care 
    not to get fuel on your 
    clothing. If this happens, 
    change your clothing 
    Unit vibrations can cause 
    an improperly tightened 
    fuel filler cap to loosen or 
    come off and spill quanti-
    ties of fuel. In order to 
    reduce the risk of fuel 
    spillage and fire, tighten 
    the fuel filler cap by hand 
    as securely as possible. 
    							FS 90, FS 90 R
    7 Before Starting
    Always check your power tool for proper 
    condition and operation before starting, 
    particularly the throttle trigger, throttle 
    trigger lockout, slide control / stop 
    switch, cutting attachment, deflector and 
    harness. The throttle trigger must move 
    freely and always spring back to the idle 
    position. Never attempt to modify the 
    controls or safety devices.
    Check fuel system for leaks, especially 
    the visible parts, e.g., filler cap, hose 
    connections, manual fuel pump (only for 
    power tools equipped with a manual fuel 
    pump). Do not start the engine if there 
    are leaks or damage – risk of fire! Have 
    the machine repaired by a servicing 
    dealer before using it.
    Never operate your power tool if it is 
    damaged, improperly adjusted or 
    maintained, or not completely or 
    securely assembled.
    Do not attach any cutting attachment to 
    a unit without proper installation of all 
    required parts. Failure to use the proper 
    parts may cause the blade or head to fly 
    off and seriously injure the operator or 
    The cutting attachment must be properly 
    tightened and in safe operating 
    condition. Inspect for loose parts (nuts, 
    screws, etc.) and for cracked or 
    damaged heads or cracked, bent, 
    warped or damaged blades. Replace 
    damaged heads or blades before using 
    the power tool. Always keep blades 
    Keep the handles clean and dry at all 
    times; it is particularly important to keep 
    them free of moisture, pitch, oil, fuel mix, 
    grease or resin in order for you to 
    maintain a firm grip and properly control 
    your power tool.
    Check that the spark plug boot is 
    securely mounted on the spark plug – a 
    loose boot may cause arcing that could 
    ignite combustible fumes and cause a 
    As can be seen in that chart, some 
    cutting attachments may require you to 
    change your deflector, handle and / or 
    Keep the deflector (and the attached 
    skirt where appropriate) adjusted 
    properly at all times (see chapters on 
    "Mounting the Deflector" and "Mounting 
    the Cutting Attachment" of your 
    instruction manual).To reduce the risk 
    of personal injury 
    to the operator 
    from blade or line 
    contact and 
    thrown objects, 
    make sure your 
    unit is equipped 
    with the proper 
    deflector, handle 
    and harness for 
    the type of cutting 
    attachment being 
    used (see chart in 
    the chapter on 
    "Approved Combi-
    nations of Cutting 
    Deflector, Handle 
    and Harness".) 
    							FS 90, FS 90 R
    8 Arrows on the deflector (A) and limit 
    stop (B) (as seen from the underside) 
    show the correct direction of rotation of 
    the cutting attachment. When viewed 
    from above, however, the cutting 
    attachment rotates counterclockwise.
    Adjust carrying harness and hand grip to 
    suit your size before starting work. The 
    machine should be properly balanced as 
    specified in your instruction manual for 
    proper control and less fatigue in 
    operation. To be better prepared in case 
    of an emergency, practice releasing the 
    unit from the harness as quickly as 
    Start the engine at least 10 feet (3 m) 
    from the fueling spot, outdoors only.
    For specific starting instructions, see the 
    appropriate section of your manual. 
    Place the power tool on firm ground or other solid surface in an open area. 
    Maintain good balance and secure 
    To reduce the risk of injury from blade or 
    line contact, be absolutely sure that the 
    cutting attachment is clear of you and all 
    other obstructions and objects, including 
    the ground, because when the engine 
    starts at starting-throttle, engine speed 
    will be fast enough for the clutch to 
    engage and move the cutting 
    Once the engine has started, 
    immediately blip the throttle trigger, 
    which should release the starting throttle 
    and allow the engine to slow down to 
    With the engine running only at idle, 
    attach the power tool to the spring hook 
    of your harness (see appropriate 
    chapter of this manual).
    Your power tool is a one-person 
    machine. Do not allow other persons in 
    the general work area, even when 
    To reduce the risk of injury from loss of 
    control, do not attempt to "drop start" 
    your power tool.
    When you pull the starter grip, do not 
    wrap the starter rope around your hand. 
    Do not let the grip snap back, but guide 
    the starter rope to rewind it properly. Failure to follow this procedure may 
    result in injury to your hand or fingers 
    and may damage the starter 
    Important Adjustments
    To reduce the risk of personal injury 
    from loss of control or contact with the 
    running cutting attachment, do not use 
    your unit with incorrect idle adjustment. 
    At correct idle speed, the cutting 
    attachment should not move. For 
    directions on how to adjust idle speed, 
    see the appropriate section of your 
    instruction manual.
    If you cannot set the correct idle speed, 
    have your STIHL dealer check your 
    power tool and make proper 
    adjustments and repairs.
    During Operation
    Holding and Controlling the Power Tool
    Always hold the unit firmly with both 
    hands on the handles while you are 
    Wrap your fingers and thumbs around 
    the handles, keeping the handles 
    cradled between your thumb and 
    forefinger. Keep your hands in this 
    position to have your power tool under 
    control at all times. Make sure your 
    trimmer handles and grips are in good 
    condition and free of moisture, pitch, oil, 
    fuel mix or grease.
    Make sure you always have good 
    balance and secure footing.
    000BA006 KN
    000BA007 KN 
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