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Stihl Ht 75 Owners Manual

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    							30 english
    HT 70, HT 75Standard Setting:Shut off the engine.
    :Check chain tension.
    :Check the air filter and clean or 
    replace as necessary.
    :Check spark arresting screen* and 
    clean or replace as necessary.
    :Check adjustment of the throttle 
    cable and readjust if necessary – 
    see Adjusting the Throttle Cable.
    :Turn high speed screw (H) 
    counterclockwise (max. 3/4 turn) 
    as far as stop.
    :Carefully screw the low speed 
    screw (L) down onto its seat. Then 
    open it one turn counterclockwise.
    :Start and warm up the engine.
    :Adjust idle speed with the idle speed 
    screw (LA) so that the chain does 
    not rotate.Fine Tuning A slight correction of the setting of the 
    high speed screw (H) may be necessary 
    if engine power is not satisfactory when 
    operating at high altitude or at sea level.
    * see Guide to Using this Manual”Rule of thumb
    :Turn high speed screw (H) about 
    1/4 turn for every 1000m (3300 ft) 
    change in altitude.
    Conditions for adjustment
    :Carry out standard setting.
    :Warm up engine for about 5 
    :Open the throttle wide.
    At high altitude
    :Turn high speed screw (H) clock-
    wise (leaner) no further than stop 
    until there is no noticeable increase 
    in engine speed.
    At sea level
    :Turn high speed screw (H) counter-
    clockwise (richer) no further than 
    stop until there is no noticeable 
    increase in engine speed.
    It is possible that maximum engine 
    speed may be reached with the 
    standard setting in each case.
    Adjusting Idle SpeedIt is usually necessary to change the 
    setting of the idle speed screw (LA) 
    after every correction to the low speed 
    screw (L).
    :Warm up engine for about 5 
    Engine stops while idling
    :Turn idle speed screw (LA) slowly 
    clockwise until the engine runs 
    smoothly – chain must not rotate.
    Chain rotates when engine is idling
    :Turn idle speed screw (LA) slowly 
    counterclockwise until chain stops 
    rotating and then turn the screw 
    about another 1/2 to 1 turn in the 
    same direction. 
    Erratic idling behavior, engine stops 
    even though setting of LA screw is 
    correct, poor acceleration
    Idle setting too lean:
    :Turn low speed screw (L) 
    counterclockwise (about 1/4 turn) 
    until the engine runs and 
    accelerates smoothly. 
    							31 HT 70, HT 75english
    Erratic idling behavior
    Idle setting too rich:
    :Turn low speed screw (L) clockwise 
    (about 1/4 turn) until the engine runs 
    and accelerates smoothly.
    If the engine is low on power, check the 
    spark arresting screen in the muffler.
    :Lift spark arresting screen and pull it 
    out sideways.
    :Clean spark arresting screen if 
    :If screen is damaged or coked up, fit 
    a new one.
    :Refit the spark arresting screen.
    * see “Guide to Using this Manual”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.
    Spark Arresting Screen* in 
    392BA035 KN
    Checking the Spark Plug
    000BA002 KN 
    							32 english
    HT 70, HT 75 If engine is down on power, difficult to 
    start or runs poorly at idling speed, first 
    check the spark plug.
    :Remove spark plug - see “Starting / 
    Stopping the Engine“.
    :Clean dirty spark plug.
    :Check electrode gap (A) and 
    readjust if necessary – see 
    :Use only resistor type spark plugs 
    of the approved range.
    Rectify problems which have caused 
    fouling of spark plug: 
    :Too much oil in fuel mix.
    :Dirty air filter.
    :Unfavorable running conditions, 
    e.g. operating at part load.
    Fit a new spark plug after approx. 100 
    operating hours 
    or earlier if the electrodes are badly 
    eroded.To reduce the risk of fire and burn 
    injury, use only spark plugs 
    authorized by STIHL. Always press 
    spark plug boot (2) snugly onto 
    spark plug terminal (1) of the proper 
    size. (Note: If boot has detachable 
    SAE adapter nut, it must be 
    A loose connection between spark 
    plug boot and ignition wire 
    connector in the boot may create 
    arcing that could ignite combustible 
    fumes and cause a fire.
    Removing the Starter Cover:Take out the screws (1).
    :Remove the cable lug, if fitted.
    :Lift the starter cover (2) away from 
    the tank (3) and pull it out from 
    under the shroud (4).
    000BA036 TR
    Replacing the Starter Rope 
    and Rewind Spring
    386BA004 KN
    							33 HT 70, HT 75english
    Removing the Rope Rotor:Take out the screw (5).
    :Remove the rope rotor very 
    The rewind spring is seated in the 
    rope rotor and may pop out and 
    uncoil if care is not taken. 
    The pieces of broken spring may be 
    under tension and fly apart 
    unexpectedly when you remove the 
    rope rotor. To help reduce the risk of 
    injury, wear face protection and 
    Replacing the Starter Rope:Use a screwdriver to pry the cap (6) 
    out of the starter grip.
    :Remove remaining rope from the 
    rotor and grip, making sure the 
    ElastoStart sleeve is not pushed out 
    of the grip.
    :Tie a simple overhand knot in the 
    end of the new starter rope (see 
    Specifications) and then thread the 
    rope through the top of the grip and 
    the rope bush (7).
    :Refit the cap in the grip.:Pull the rope through the rotor and 
    secure it with a simple overhand 
    :Go to Installing the rope rotor.
    Replacing a Broken Rewind 
    SpringTwo types of replacement spring are 
    available from the factory:
    – A ready-to-fit rewind spring secured 
    with a wire retainer.
    – A rope rotor with pre-installed 
    rewind spring.
    Installing the ready-to-fit rewind 
    :Lubricate the spring with a few 
    drops of non-resinous oil – see 
    Special Accessories – do not open 
    the wire retainer!
    392BA014 KN
    392BA015 KN
    392BA024 KN 
    							34 english
    HT 70, HT 75 :Carefully remove the parts of the old 
    spring from the starter cover and 
    rope rotor.
    :Insert the new rewind spring in the 
    rope rotor and, at the same time, 
    engage the outer spring loop in the 
    rotor’s recess – the wire retainer 
    slips off in this process. 
    If the spring pops out and uncoils, 
    refit it in the counterclockwise 
    direction, starting outside and 
    working inwards.
    :Go to Installing the Rope Rotor.
    Installing rope rotor with rewind 
    :Carefully unpack the new rope rotor 
    with rewind spring. The spring may 
    pop out if not handled with care –
    risk of injury.
    :Lubricate the spring with a few 
    drops of non-resinous oil – see 
    Special Accessories.
    :Go to Installing the Rope Rotor.
    Installing the Rope Rotor:Check dimension a for inner spring 
    anchor loop and bend it slightly if 
    :Coat rope rotor bearing bore with 
    non-resinous oil – see Special 
    :Slide the rotor onto the starter post – 
    turn it back and forth until the rewind 
    spring anchor loop (8) engages.
    :Insert the screw (5) and tighten it 
    down securely.
    :Go to Tensioning the Rewind 
    Tensioning the Rewind Spring:Make a loop in the unwound 
    starter rope and use it to turn 
    the rope rotor six full revolutions 
    counterclockwise. Hold the rotor 
    steady – straighten the twisted rope 
    – release the rotor – 
    let go of rope slowly so that it winds 
    onto the rotor.
    :Check spring tension:
    – The starter grip must be firmly 
    seated in the rope guide bush. 
    If the grip droops to one side: Add 
    one more turn on rope rotor to 
    increase spring tension.
    – When the starter rope is fully 
    extended it must be possible to 
    rotate the rotor another half turn. If 
    this is not the case, the spring is 
    overtensioned and could break. 
    Take one turn of rope off the rotor.
    :Go to Fitting the Starter Cover.
    389BA029 KN
    a = 2mm
    (0.08 in)
    392BA025 KN
    392BA044 KN 
    							35 HT 70, HT 75english
    Fitting the Starter Cover:Push the upper mounting boss 
    under the shroud –
    line up the tank and push the lower 
    part of cover onto the tank.
    :Insert and tighten down the housing 
    Secure cable lug (arrow) in position 
    (if fitted on your machine).For periods of about 3 months or longer:
    :Drain and clean the fuel tank in a 
    well ventilated area.
    :Run engine until carburetor is dry, 
    this helps prevent the carburetor 
    diaphragms sticking together.
    :Remove the saw chain and guide 
    bar, clean them and spray with 
    corrosion inhibiting oil.
    :Thoroughly clean the machine, 
    pay special attention to the cylinder 
    fins and air filter.
    :If you use a biological chain and bar 
    lubricant, e.g. STIHL BioPlus, 
    completely fill the chain oil tank.
    :Store the machine in a dry and high 
    or locked location, out of the reach 
    of children and other unauthorized 
    Replace the chain sprocket after using 
    two chains!
    Replace sooner if the wear marks 
    on the sprocket are deeper than 
    about 0,02 (0.5 mm)(dimension a) 
    since this would otherwise shorten 
    the life of the chain.
    Use gauge – see Special 
    Accessories – to check the depth of the 
    wear marks.
    It is best to use two chains in 
    rotation with one sprocket.
    Use only original STIHL chain sprockets!
    410BA019 KN
    Storing the Machine Checking the Chain 
    390BA012 KN 
    							36 english
    HT 70, HT 75HT 70:Remove the chain sprocket cover, 
    chain and guide bar.
    :Use a screwdriver to remove the E-
    clip (1).
    :Pull the washer (2) and sprocket (3) 
    off the gear shaft.
    :Clean the stub of the gear shaft and 
    lubricate with STIHL grease – see 
    Special Accessories.
    :Fit the new chain sprocket on the 
    gear shaft.
    :Fit the washer and E-clip on the 
    gear shaft.
    HT 75The chain sprocket is driven through a 
    friction clutch. It may only be replaced by 
    an authorized STIHL servicing dealer.
    Replacing Chain SprocketHT 70
    386BA014 KN 
    							37 HT 70, HT 75english
    Correctly sharpened chainA properly sharpened chain slices 
    through wood effortlessly and requires 
    very little feed pressure.
    Do not work with a dull or damaged saw 
    chain as it will increase the physical 
    effort required, produce unsatisfactory 
    results and a higher rate of wear.
    :Clean the chain. 
    :Check the chain for cracks in the 
    links and damaged rivets.
    :Replace any damaged or worn parts 
    of the chain and match the new 
    parts to the shape and size of the 
    original parts by filing back as 
    It is necessary to comply with the 
    angles and dimensions specified 
    below. If the saw chain is 
    incorrectly sharpened – especially 
    if the depth gauges are too low – 
    there is an increased risk of 
    kickback and resulting injury!The pruner’s saw chain cannot be 
    locked in place on the guide bar. 
    Therefore, it is best to remove the 
    chain from the bar and resharpen it 
    on a workshop sharpening tool 
    (FG 2, HOS, USG).
    :Select the appropriate sharpening 
    tools for the chain pitch. 
    See Specifications for the 
    permitted chain pitches.
    The chain pitch (e.g. 3/8) is marked on 
    the depth gauge of each cutter.
    Use only special saw chain files! 
    Other files have the wrong shape and 
    cut.Select the file diameter according to the 
    chain pitch (se table Sharpening Tools 
    at the end of this chapter).
    You must also observe the following 
    angles when resharpening the chain 
    A =Filing angle
    B =Side plate angle
    Cutter shape: Micro = Semi-chisel
    Specified angles A and B are more 
    readily obtained if recommended files or 
    sharpening tools and correct settings 
    are used.Maintaining and Sharpening 
    Saw Chain
    689BA020 KN
    Chain type Angle (°)
    Picco Micro Mini (PMN) 30 85
    689BA021 KN 
    							38 english
    HT 70, HT 75 Furthermore, the angles must be the 
    same on all cutters. If angles are uneven 
    the chain will run roughly, not in a 
    straight line, wear quickly and break 
    As these requirements can be met only 
    after sufficient and constant practice:
    :Use a file holder
    A file holder must be used for manual 
    resharpening of saw chain (see table 
    Sharpening Tools). The correct filing 
    angles are marked on the file holder.
    For checking anglesUse a STlHL filing gauge (see table 
    Sharpening Tools). This is a universal  
    tool for checking the filing and side plate 
    angles, depth gauge setting and cutter 
    length. It also cleans the guide bar 
    groove and oil inlet holes.File correctly:If you use an FG 2, HOS or USG 
    sharpener: Remove the chain from 
    the bar and sharpen according to 
    instructions supplied with the tool.
    :Sharpen chain frequently; take 
    away as little metal as possible – 
    two or three strokes of the file are 
    usually enough.:Hold the file horizontally (at right 
    angle to side of guide bar) and file 
    according to the angles marked on 
    the file holder. Rest the file holder on 
    the top plate and depth gauge.
    :Always file from the inside to the 
    outside of the cutter.
    :The file only sharpens on the 
    forward stroke – lift the file off the 
    cutter on the backstroke.
    :Avoid touching the tie straps and 
    drive links with the file.
    689BA025 KN
    85° 70°
    0° 35°
    10° 30°
    689BA022 KN
    689BA018 KN
    689BA043 KN 
    							39 HT 70, HT 75english
    :Rotate the file at regular intervals 
    while filing to avoid one-sided wear.
    :Use a piece of hardwood to remove 
    burrs from cutting edge.
    :Check angles with the filing gauge.
    All cutters must be the same length.
    If the cutters are not the same length, 
    they will have different heights. This 
    makes the chain run roughly and 
    increases the risk of breakage of the 
    :Find the shortest cutter and then file 
    all other cutters back to the same 
    length – it is best to have this work 
    done in a workshop on an electric 
    Depth gauge settingThe depth gauge determines the height 
    at which the cutter enters the wood and 
    thus the thickness of the chip removed.
    Distance between depth gauge and 
    cutting edge a =  0.018(0.45 mm).
    This setting may be increased by 0.008  
    (0.2mm) for cutting softwood in mild 
    weather season – no frost.Lowering depth gaugesThe depth gauge setting is reduced 
    when the chain is sharpened because 
    the top plate of the cutter slopes 
    downward towards the back. 
    :Check the depth gauge setting 
    every time you sharpen the chain.:Place a filing gauge (1) that 
    matches the chain pitch on the 
    chain – if the depth gauge projects 
    from the filing gauge, the depth 
    gauge has to be lowered.
    :File down the depth gauge until it is 
    level with the filing gauge.
    689BA023 KN
    689BA047 KN
    689BA051 KN 
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