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Stihl 108 User Guide

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    Circularsawblade 200
    (chisel andscratcher tooth)
    Fitthe appropriate stop
    before mounting circularsawblade.
    Fitting thestop seechapter Mounting
    the Deflector.
    30
    Mounting circularsawblade
    •Layyour brushcutter onitsback
    with thegear head facing up.
    • Position sawblade
    (3)on
    the thrust plate(4)-
    teeth mustpointinclockwise
    direction.
    • Slipthethrust washer
    (5)
    andrider plate(6)over
    the drive shaft
    (7).
    •Block thedrive shaft.
    • Screw mounting nut
    (8)counterclockwise onto
    drive shaftandtighten down
    securely.
    Releasing mountingnut
    •Block thedrive shaftand
    unscrew themounting nut
    clockwise.
    Ifthe mounting nutbecomes slackdue
    to frequent loosening andretightening, fit
    a new one. 
    						
    							Fuel
    Yourtwo-strokeenginerequires a
    mixture ofbrand-name gasolineand
    quality two-stroke engineoilwith the
    classificationTe.
    Useregular branded unleaded gasoline
    with aminimum octanenumber of
    90 ROZ (U.S.A./Canada: pumpoctane
    min. 89!).
    Iftheoctane number ofthe
    regular gradegasoline
    inyourarea is
    lower
    us5=lpremium unleaded fuel.
    Fuel withalower octane number may
    result
    inpreignition (causingpinging)
    which
    isaccompanied byan increasein
    engine temperature. This,inturn,
    increases therisk ofthe piston seizure
    and damage tothe engine.
    The chemical composition ofthe fuel
    is
    also important. Somefueladditives not
    only detrimentally affectelastomers
    (carburetor diaphragms, oilseals, fuel
    lines etc.), butmagnesium castingsas
    well. This could cause running problems
    or even damage theengine. Forthis
    reason
    itisessential thatyou useonly
    name branded fuels!
    Use only STIHL two-stroke engineoilor
    equivalent brandedtwo-stroke air-cooled
    engine oilswith theclassification TCfor
    mixing.
    We recommend STIHL
    50:1two-stroke
    engine oilsince itis specially formulated
    for use
    inSTIHlengines. Themixratio
    with
    STIHloilis50:1(50 parts gasoline
    to 1part oil),or
    25:1(25parts gasoline to
    1 part oil)with other branded two-stroke­
    air-cooled engineoils. Do
    not use BIAor
    TCW(two-stroke
    water cooled) mixoils!
    Take carewhen handling gasoline.
    Avoid directcontact withtheskin and
    avoid inhaling fuelvapour.
    The canister shouldbekept tightly
    closed
    inorder toavoid anymoisture
    getting intothemixture.
    The fueltank andthecanister
    inwhich
    fuel mixisstored should becleaned
    from timetotime.
    Fuel mixages:
    Only mixsufficient fuelforafew days
    work, nottoexceed 30days ofstorage.
    Store
    inapproved safetyfuel-canisters
    only. When mixing, pouroilinto the
    canister first,andthen addgasoline. Gaso-
    STIHL Otherbranded
    line engineoil
    TCoils
    50:125:1
    Liters Liters(cc)
    Liters (cc)
    1 0.02 (20)0.04 (40)
    5 0.10(100) 0.2(200)
    10 0.20(200)
    OA(400)
    15
    ,:-0.30(300) 0.6(600)
    20
    OAO(400) 0.8(800)
    25 0.50(500) 1.0
    (1000)
    Gaso- STIHL Otherbranded
    line engineoil TCoils
    50:125:1
    US gal. US
    fl.oz USfl.oz
    1 2.6
    5.1
    21/26A12.8
    5 12.8
    25.6
    31 
    						
    							FuelingFittingtheHarness
    Beforefueling, cleanthefiller capand
    the area around it
    toensurethatnodirt
    falls intothetank.
    Always thoroughly shakethemixture in
    the canister beforefueling yourmachi­
    ne. Change
    thefuel pick upbody every year.
    Before storing yourmachine foralong
    period, drainandclean thefuel tank and
    run engine untilcarburetor is
    dry.
    Modelswithaloop handle comewithout
    a harness (available asspecial acces­
    sory forthese models).
    Shoulder strap
    Useofthe carrying strapisdescribed
    in chapters SafetyPrecautions and
    Selecting theCutting Tool.
    Warning!Inordertoreduce therisk of
    bums orother personal injuryfromesca­
    ping gasvapor andfumes, remove the
    fuel filler capcarefully soastoallow any
    pressure build-up
    inthetanktorelease
    slowly.
    WarningAfter fueling, tightenfuelcap
    assecurely aspossiblebyhand.
    32
    •....,.Put onthe shoulder strap(1).
    Adjust lengthuntilthespring
    hook (3)rests against yourrighthip. 
    						
    							Fullharness
    • Putonthe fullharness (2).
    • Adjust lengthuntilthespring
    hook (3)rests against yourrighthip.
    Use ofthe carrying strapisdescribed
    inchapters SafetyPrecautions and
    Selecting theCutting Tool. Balancing
    thebrushcutter
    • Attach thespring hook
    (3)totheclamp(4)onthe drive shaft­
    slacken thescrew (5).
    • Slide theclamp upordown
    the drive shaft.
    •
    Tightenthe screw moderately. •
    Letgoofthe brush cutter andcheck
    toseehowitisbalanced:
    mowing heads,FixedLineHead
    and
    brush knifemust restlightly
    onthe
    ground. Circular sawblades muststay
    abottt30cm/1ft(A)clear ofthe
    ground.
    •
    Tightenthe screw firmly.
    33 
    						
    							Starting
    1
    •Observe safetyprecautions -see
    section SafetyPrecautionsinthis
    manual.
    • Hold down thethrottle trigger
    interlock (1)and squeeze
    the throttle trigger(2).
    • Move theslide control (3)
    toSTART position.
    • Now release thethrottle trigger, slide
    control andtrigger interlock
    inthatorder=Thisisthe
    starting-throttle position.
    34
    Ifengineiscold:
    Setthechoke lever(4)to.L
    Ifengineiswarm:
    Set thechoke lever(4)to...
    Also usethissetting ilengine hasbeen
    running but
    isstillcold. •
    Puttheunit onthe ground:
    Itmust restsecurely onthe engine
    support anddeflector. Checkthat
    the cutting tool
    isnottouching the
    ground orany other obstacles.
    • Make sureyouhave afirm
    looting: Holdtheunit with youleft
    hand andpress itdown
    firmly ­
    yourthumb shouldbeunderthe
    housing.
    • Donot stand orkneel
    onthe drive
    shaft! 
    						
    							~oo~
    ((\\3))
    2
    •Pullthestarter gripslowly withyour
    right hand untilyoufeel
    itengage ­
    and then give
    itabrisk strong pull.
    Do not pull outstarter ropemore
    than 70cm (27)-
    itmight break.
    Do not letthe starter gripsnap
    back -guide
    itslowly intothe
    housing sothat thestarter rope
    can rewind properly. When
    engine beginstofire:
    Ifengine iscold:
    Set choke lever(4)
    to-
    andcontinue cranking untilengine runs.
    Ifengineiswarm:
    Continue crankinguntilengine
    runs_
    Assoon aswarm engine runs:
    • Blipthethrottle trigger(2)-
    the slide control (3)moves tothe
    runpositionI,and theengine
    returns
    toidling speed.
    •
    Make~urecarburetor iscorrectly
    adj,usted-cutting toolmust not
    rotate whenengine
    isidling.
    Your brushcutter
    isready for
    operation.
    35 
    						
    							Toshutdown engine:
    • Move slidecontrol (3)
    toSTOP.
    At very lowoutside temperatures:
    Allow engine towarm up
    As soon asengine runs:
    • Blipthethrottle trigger-
    the slide control
    (3)moves tothe
    run position
    I,and theengine
    returns toidling speed.
    • Open throttle slightly -
    warm upengine forshort period.
    36
    Ifthe engine doesnt start:
    Ifyoudidnot move thechoke
    lever
    to.L
    quickly enough aftertheengine
    began tofire, thecombustion chamber
    is flooded.
    Remove sparkplugterminal
    (5)-
    • Unscrew anddryoffthe
    spark plug.
    • Setslide control
    toSTOP.
    • Open thethrottle fully.
    • Pullthestarter ropeseveral timesto
    clear thecombustion chamber. •
    Refit thespark plugandconnect
    the spark plugterminal.
    • Setslide control toSTART.
    • Setchoke lever
    to...
    even ifengineiscold.
    •
    Nowstart theengine.
    Fuel tank rununtil dryand then
    refueled
    • Continue cranking-
    Engine willnot start immediately
    because fuelpump hastobe pri­
    med withfuel. 
    						
    							AdjustingCarburetor
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    Thecarburetor hasbeen adjusted for
    optimum performance underthe
    barometric pressureandclimatic
    conditions atthe factory.
    Basic setting
    Thissettingisthestarting pointforfine
    tuning andcanbeused asthe
    standard setting.
    •Check airfilter andclean it if
    necessary.
    • Carefully screwthehigh speed
    adjusting screw(H) and lowspeed
    adjusting screw(L)down ontotheir
    seats (clockwise) andmake the
    following adjustments: H
    Open 1full turn
    L Open 1full tum
    • Start theengine andadjust idling
    speed withtheidle speed adjusting
    screw
    LAor LD:
    cutting toolmust notrotate.
    This standard setting
    istheoptimum
    setting
    ofthe high speed adjusting screw
    for normal operation atan altitude of
    about 300m/1000
    Itabove sealevel.
    Itensures yourmachine willdeliver
    maximum power,befuel efficient and
    operate reliably.
    Itmaybenecessary fine-tunethe
    carburetor
    ifoperatingconditionschange,
    e.g. higher orlower altitudes, extreme
    changes
    inhumidity andtemperature or
    ifyoufitadifferent cuttingtool:
    Thefinetuning procedures described
    below ensure maximum performance
    under
    t~enewoperating conditions.
    37 
    						
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    II
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    FS108(I ,FS108( I ,
    Finetuning
    •Mount thecutting tool.
    Machines withcutting head:
    •Trim linetocorrect length:
    Lines mustextend asfar asline
    limiting bladeonthe deflector
    • Carry outthebasic setting.
    • Warm upengine byrunning
    itfor
    about 1minute atfull throttle and
    then return
    toidlespeed.
    • Back offhigh speed adjusting screw
    (H)onehalfturn (counterclockwise).
    • Runengine atfull throttle androtate
    high speed adjusting screw
    (H)
    carefullyclockwise untilyouhear
    38
    nofurther increaseinRPM­
    back offscrew oneeighth turn.
    Machines withmetal cutting tool:
    Atachometer isnecessary forthe
    following adjustment.
    Ifnotachometerisavailable,.....,.
    do not turn screws beyond thebasic
    setting.
    • Carry outthebasic setting.
    • Warm upengine byrunning
    itfor
    about 1minute atfull throttle and
    then return toidle speed. •
    Back offhigh speed adjusting screw
    (H)onehalfturn (counterclockwise).
    • Runengine atfull throttle and
    rotate highspeed adjusting screw
    (H)carefullyclockwise until
    maximum permissible speedof
    12,000 RPM
    isreached.
    Turning thescrew
    (H)any further
    in the clockwise directionwill
    make thefuel-air mixture too
    lean -
    thiscould damage theengine! 
    						
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    FS
    108( I IFS108( IIFS108( II
    Adjustingidlespeed
    Itisusually necessary tochange
    the setting ofthe idle speed
    adjusting screw
    (LAorLD)after every
    correction
    tothe low speed
    adjusting screw
    (L).
    Engine stopswhileidling
    Turntheidle speed
    adjusting screw
    (LAorLD)
    clockwise untilengine runs
    smoothly -cutting
    tool must notrotate.
    Cutting toolrotates when
    engine isidling
    Turn theidle speed adjusting
    screw
    (LA orLD)counterclockwise
    until cutting toolstops rotating ­
    then back offscrew about
    another onehalftum from that
    position.
    Erratic idlingbehavior,
    poor acceleration
    Idlesetting istoo lean.
    Turn thelow speed adjusting
    screw
    (L)counterclockwise until
    engine runsandaccelerates
    smoothly.
    Exhaust smokesatidle speed
    Idlesetting istoo rich.
    Turn thelow speed adjusting
    screw
    (L)clockwise until
    engine speeddrops. Thenturn
    screw backonequarter turn
    and
    ch~kthat engine still
    accelerates smoothlywhen
    you open thethrottle.
    39 
    						
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