Stihl FS 40, FS 50 Instruction Manual

STIHL FS 40, 50

WARNING

Read Instruction Manual thoroughly before use and follow all safety precautions – improper use can cause serious or fatal injury.

ADVERTENCIA

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 mortales.

Instruction Manual Manual de instrucciones

Instruction Manual 1 - 42

Manual de instrucciones 43 - 89

Contents

English

Guide to Using this Manual 2 Safety Precautions and Working

Techniques 3 Approved Combinations of Cutting

Attachment, Deflector, Handle and Harness 15

Mounting the Loop Handle 16 Mounting the Deflector 16 Mounting the Cutting Attachment 17

Original Instruction ManualPrinted on chlorine-free paper

Fuel 19 Fueling 20 Starting / Stopping the Engine 22 Operating Instructions 24 Cleaning the Air Filter 24 Engine Management 25 Adjusting the Carburetor 25 Spark Plug 26 Engine Running Behavior 27 Storing the Machine 27 Maintaining the Mowing Head 27 Inspections and Maintenance by

Dealer 31

Printing inks contain vegetable oils, paper can be recycled.

Maintenance and Care 32 Main Parts 34 Specifications 35 Maintenance and Repairs 36 Disposal 37 Limited Warranty 37 STIHL Incorporated Federal

Emission Control Warranty Statement 37

STIHL Incorporated California Exhaust and Evaporative Emissions Control Warranty Statement 39

Trademarks 41

Allow only persons who fully understand this manual to operate your trimmer.

To receive maximum performance and satisfaction from your STIHL trimmer, 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. 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 manual.

WARNING

Because a trimmer 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.

0458-546-8621-D. VB0.L21.

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FS 40, FS 40 C, FS 50, FS 50 C

English

Guide to Using this Manual

Pictograms

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 machine.

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 lubricant

Air intake summer mode

Air intake winter mode

Handle heating

Symbols in Text

Many operating and safety instructions are supported by illustrations.

The individual steps or procedures described in the manual may be shown in different ways:

N A bullet indicates 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. For example:

N Remove the screw (1) N Pull the spark arresting screen (2)

upwards out of the muffler

In addition to the operating instructions, this manual may contain paragraphs that require your special attention. Such paragraphs are indicated with the symbols and signal words described below:

DANGER

Indicates a hazardous situation that, if not avoided, will result in death or serious injury.

WARNING

Indicates a hazardous situation that, if not avoided, could result in death or serious injury.

NOTICE

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.

FS 40, FS 40 C, FS 50, FS 50 C

English

Safety Precautions and Working Techniques

Because a trimmer is a high-speed, fast-cutting power tool, special safety precautions must be observed to reduce the risk of personal 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.

The terminology utilized in this manual when referring to the power tool reflects the type of cutting attachments that 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).

WARNING

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. To reduce the risk of severe or fatal injury from blade contact and / or loss of control, never attempt to use a metal blade on this trimmer.

Have your STIHL dealer show you how to operate your power tool. Observe all applicable local safety regulations, standards and ordinances.

WARNING

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.

WARNING

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. Thrown objects, including broken heads or blades, may result in serious or fatal injury to the operator or bystanders.

Use your trimmer equipped with the appropriate cutting attachment only for cutting grass and similar material.

WARNING

Do not use it for other purposes, since misuse may result in personal injury or property damage, including damage to the machine.

WARNING

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.

WARNING

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. 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.

Safe use of a trimmer involves

1. the operator

2. the power tool

3. the use of the power tool.

THE OPERATOR

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.

WARNING

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.

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WARNING

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

warm.

– Keep the AV system well

maintained. A power tool with loose components or with damaged or worn AV buffers 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.

WARNING

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

WARNING

To reduce the risk of injury, the operator should wear proper protective apparel.

thrown back by the rotating cutting attachment. Thrown objects may also ricochet and strike the operator.

WARNING

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 glasses.

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 regularly.

Be particularly alert and cautious when wearing hearing protection because your ability to hear warnings (shouts, alarms, etc.) is restricted.

WARNING

The deflector provided with your power tool will not protect the operator from all foreign objects (gravel, glass, wire, etc.)

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English

389BA019 KN

Always wear heavy duty work gloves (e.g. made of leather or other wear resistant material) when handling the machine, blade and the cutting attachment. Heavy-duty, nonslip gloves improve your grip and help to pro tect your hands.

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 barefoot.

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.

Good footing is very important. Wear sturdy boots with nonslip soles. Steel-toed safety boots are recommended.

THE POWER TOOL

For illustrations and definitions of the power tool parts see the chapter on "Main Parts."

WARNING

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.

THE USE OF THE POWER TOOL

Transporting the Power Tool

WARNING

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.

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 you.

WARNING

Always shut off the engine and make sure the cutting attachment has stopped before putting a trimmer down. When transporting it in a vehicle, properly secure it to prevent turnover, fuel spillage and damage to the unit.

Fuel Your STIHL power tool uses an oil-

gasoline mixture for fuel (see the "Fuel" chapter in this instruction manual).

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English

WARNING

Gasoline is an extremely flammable fuel. If spilled and ignited by a spark or other ignition source, it can cause fire and seri 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 system.

Fueling Instructions

WARNING

To reduce the risk of fire and serious personal injury, always place the power tool on the ground before attempting to fuel the machine.

WARNING

Pick a Safe Location To reduce the risk of fire and explosion,

fuel your power tool in a well-ventillated area, outdoors away from flames, pilot lights, heaters, electric motors, and other sources of ignition. Vapors can be ignited by a spark or flame many feet away. 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 power tool. Take care not to get fuel on your clothing. If this happens, change your clothing immediately.

Allow the Power Tool to Cool Before Removing the Fuel Cap

WARNING

Gasoline vapor pressure may build up inside the fuel tank. The amount of pressure depends on a number of factors such as the fuel used, altitude and temperature. To reduce the risk of burns and other personal injury from escaping gas, vapor and fumes, always shut off the engine and allow it to cool before removing the fuel cap.

The engine is air cooled. When it is shut off, cooling air is no longer drawn across the cylinder and engine temperatures will rise for several minutes before starting to cool. In hot environments, cooling will take longer. To reduce the risk of burns and other personal injury from escaping gas, vapor and fumes, allow the power tool to cool. If you need to refuel before completing a job, turn off the machine and allow the engine to cool before opening the fuel tank.

Fuel Spraying or “Geysering”

WARNING

Removing the cap on a pressurized fuel tank can result in gasoline, vapors and fumes being forcefully sprayed out from the fuel tank in all directions. The escaping gasoline, vapors or fumes can cause serious personal injury, including fire and burn injury, or property damage.

Sometimes also referred to as "fuel geysering," fuel spraying is an expulsion of fuel, vapors and fumes which can occur in hot conditions, or when the engine is hot, and the tank is opened without allowing the power tool to cool adequately. It is more likely to occur when the fuel tank is half full or more.

Pressure is caused by fuel and heat and can occur even if the engine has not been running. When gasoline in the fuel tank is heated (by ambient temperatures, heat from the engine, or other sources), vapor pressure will increase inside the fuel tank.

Some blends of gasoline, particularly those designed for use in winter, are more volatile and may cause tanks to pressurize more quickly or create greater pressure. At higher altitudes, fuel tank pressurization is more likely.

How to Avoid Fuel Spraying Removing the fuel cap on a pressurized

tank can result in gasoline, vapors and fumes being forcefully sprayed out from the fuel tank in all directions. To reduce the risk of burns, serious injuries or property damage from fuel spraying:

– Follow the fueling instructions in this

chapter.

– Always assume your fuel tank is

pressurized.

– Allow the power tool to cool before

removing the fuel cap.

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English

– In hot environments, cooling will

take longer.

– The engine is air cooled. When it is

shut off, cooling air is no longer drawn across the cylinder and the engine temperature will rise for several minutes before starting to cool.

After the power tool has cooled appropriately, follow the safety instructions in this chapter for removing the cap.

Never remove the fuel filler cap by turning it directly to the open position. First check for residual pressure in the tank by slowly turning the cap approximately 1/2 turn counterclockwise. The cap should be held in place by the threads while allowing residual vapor/pressure to be relieved. Once the fumes or vapor have been relieved, turn the cap further until it can be removed from the tank opening.

Use only good quality fuel that is appropriate for the season (summer v. winter blends). Some blends of gasoline, particularly winter blends, are more volatile and can contribute to fuel spraying.

Removing the Threaded Fuel Filler Cap

WARNING

After allowing the power tool to cool, remove the fuel filler cap slowly and carefully to allow any remaining pressure build-up in the tank to release:

– While maintaining steady,

downward pressure, slowly turn the cap approximately 1/2 turn counterclockwise.

– If any significant venting occurs,

immediately re-seal the tank by turning the cap clockwise to the closed position. Allow the power tool to cool further before attempting to open the tank.

– Turn the cap to the open position

only after the contents of the tank are no longer under pressure.

– Never remove the cap by turning it

directly to the open position. First allow the power tool to cool adequately and then release any residual pressure by slowly turning it approximately 1/2 turn counterclockwise.

– Never attempt to remove the cap

while the engine is still hot or running.

Installing the Threaded Fuel Filler Cap

WARNING

Unit vibrations can cause an improperly tightened fuel filler cap to loosen or come off and spill quanti ties of fuel. To reduce the risk of fuel spillage and fire, tighten the fuel filler cap by hand with as

much force as possible. Damaged or Broken Cap If your fuel cap does not tighten properly,

it may be damaged or broken. Stop using the power tool and take it to your authorized STIHL dealer for repair.

Vapor Lock

WARNING

Vapor lock occurs when fuel in the fuel line or carburetor vaporizes, causing bubbles to block the free flow of liquid fuel into the carburetor. Vapor lock cannot be relieved or affected by opening the fuel tank. Removing the fuel filler cap without first allowing the power tool to cool adequately can result in fuel spraying. Always follow the instructions in this section when removing the fuel cap.

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English

To relieve vapor lock: – Press the manual fuel pump bulb at

least 20 to 30 times – even if the bulb is already filled with fuel – to clear the vapor and send liquid fuel into the carburetor. Then start the power tool. For specific starting instructions, see the appropriate section of your instruction manual.

– If the manual fuel pump bulb will not

be filled, place the Choke Lever to the cold start position g and pull the starter cord until the engine runs. If the engine does not fire after 10 pulls in the cold start position g, place the Choke Lever to the warm start position < and start the engine in the warm start position <.

– If your power tool will not restart, or

if vapor lock occurs again, the power tool is being used in conditions too extreme for the fuel being used. Discontinue use and let the engine cool completely before attempting to start the power tool.

Before Operation

WARNING

Always check your power tool for proper condition and operation before starting, particularly the throttle trigger, throttle trigger lockout, 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.

WARNING

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 power tool repaired by a STIHL servicing dealer before using it.

WARNING

Never operate your power tool if it is damaged, improperly adjusted or maintained, or not completely and securely assembled.

WARNING

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 fire.

WARNING

Do not mount 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 bystanders.

WARNING

The cutting attachment must be properly tightened and not damaged. Inspect for loose parts (nuts, screws, etc.) and for cracked or damaged heads. Replace damaged heads before using the power tool.

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.

WARNING

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 Attachment, Deflector, Handle and Harness".)

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.)

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English

Arrow on the deflector (as seen from the underside) shows the correct direction of rotation of the cutting attachment. When viewed from above, however, the cutting attachment rotates clockwise.

Some of the following symbols may be embossed on the outside of the deflector in order to indicate the approved combination of cutting attachment and deflector.

The deflector may be used in combination with mowing heads.

The deflector must not be used in combination with mowing heads.

The deflector may be used in combination with grass cutting blades.

The deflector must not be used in combination with grass cutting blades.

The deflector may be used in combination with brush knives.

The deflector must not be used in combination with brush knives.

The deflector must not be used in combination with shredder blades.

The deflector must not be used in combination with circular saw blades.

Adjust carrying harness (if you are wearing one) 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, practise releasing the unit from the harness as quickly as possible.

For specific starting instructions, see the appropriate section of your instruction manual.

Starting 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 footing.

WARNING

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 attachment.

Once the engine has started, immediately blip the throttle trigger, which should release the starting throttle and allow the engine to slow down to idle.

With the engine running only at idle, attach the power tool to the spring hook of your harness (see appropriate chapter of this manual).

WARNING

Your power tool is a one-person machine. Do not allow other persons in the general work area, even when starting.

WARNING

To reduce the risk of injury from loss of control, do not attempt to "drop start" your power tool.

WARNING

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.

FS 40, FS 40 C, FS 50, FS 50 C

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002BA054 KN

Failure to follow this procedure may result in injury to your hand or fingers and may damage the starter mechanism.

Important Adjustments

WARNING

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.

WARNING

This unit is equipped with an ignition system that is normally in operational readiness. After the stop switch is used to stop the engine, it automatically springs back to the "on" position in order to allow easier restarting. If the engine is warm, it may be possible to start it by simply pulling the starter rope, with no further adjustments. To reduce the risk of injury, be particularly alert to keep children away from the unit.

During Operation Holding and Controlling the Power Tool

Always hold the unit firmly with both hands on the handles while you are working. 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.

WARNING

To reduce the risk of injury from loss of control, never work on a ladder or on any other insecure support. Never hold the cutting attachment above waist height.

WARNING

Never attempt to operate

your power tool with one

hand. Loss of control of

the power tool resulting in

serious or fatal injury may

result. To reduce the risk

of cut injuries, keep

hands and feet away

from the cutting attach

ment. Never touch a

moving cutting attach

ment with your hand or

any other part of your

body.

WARNING

Do not overreach. Keep proper footing and balance at all times. Special care must be taken in slippery conditions (wet ground, snow) and in difficult, overgrown terrain. Watch for hidden obstacles such as tree stumps, roots and ditches to avoid stumbling. For better footing, clear away scrub and cuttings. Be extremely cautious when working on slopes or uneven ground.

Working Conditions Operate and start your power tool only

outdoors in a well ventilated area. Operate it under good visibility and daylight conditions only. Work carefully.

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15m (50ft)

WARNING

As soon as the engine is running, this product gen erates toxic exhaust fumes containing chemi

cals, such as unburned hydrocarbons (including benzene) and carbon monoxide, that are known to cause respira

tory problems, cancer, birth defects, or other reproductive harm. Some of the gases (e.g. carbon monoxide) may be color less and odorless. To reduce the risk of serious or fatal injury/illness from inhaling toxic fumes, never run the machine indoors or in poorly venti lated locations.

WARNING

If the vegetation being cut or the surrounding ground is coated with a chemical substance (such as an active pesticide or herbicide), read and follow the instructions and warnings that accompanied the substance at issue.

WARNING

Inhalation of certain dusts, especially organic dusts such as mold or pollen, can cause susceptible persons to have an allergic or asthmatic reaction. Substantial or repeated inhalation of dust and other airborne contaminants, in particular those with a smaller particle size, may cause respiratory or other illnesses. Control dust at the source

FS 40, FS 40 C, FS 50, FS 50 C

where possible. Use good work practices, such as operating the unit so that the wind or operating process directs any dust raised by the power tool

away from the operator. Follow the recommendations of EPA/OSHA/NIOSH and occupational and trade associations with respect to dust ("particulate matter"). When the inhalation of dust cannot be substantially controlled, i.e., kept at or near the ambient (background) level, the operator and any bystanders should wear a respirator approved by NIOSH/MSHA for the type of dust encountered.

Operating Instructions

WARNING

Do not operate your power tool using the starting throttle lock, as you do not have

control of the engine speed. In the event of an emergency, switch off

the engine immediately – move the slide control / stop switch to 0 or STOP.

WARNING

The rotating cutting attachment may fling foreign objects directly or by ricochet a great distance.

To reduc e th e risk of eye and other inj ury always wear proper eye protection (see the chapter on "Proper Clothing") and

ensure that bystanders are at least 15 m (50 feet) away. To reduce the risk of damage to property, also maintain this distance from such objects as vehicles or windows. Even maintaining a minimum distance of 15 meters cannot exclude all potential risks. Any coworkers who must be in the restricted area should also wear goggles or protective glasses. Stop the engine immediately if you are approached.

WARNING

Inspect the work area: To

reduce the risk of injury,

remove stones, pieces of

metal and other solid

objects which could be

thrown 15 meters or more

by the cutting attachment

or damage the cutting

attachment or other prop

erty (e.g. parked

vehicles, windows).

WARNING

This trimmer is normally to be used at ground level with the cutting attachment parallel to the ground. Use of a trimmer above ground level or with the cutting attachment perpendicular to the ground may increase the risk of injury, since the cutting attachment is more fully exposed and the power tool may be more difficult to control.

WARNING

During cutting, check the tightness and the condition of the cutting attachment at regular short intervals with the engine and attachment stopped. If the behavior

English

of the attachment changes during use, stop the engine immediately, wait until the cutting attachment stops, and check the nut securing the attachment for tightness and the head for cracks, wear or other damage.

WARNING

A loose head may vibrate, crack, break or come off the trimmer, which may result in serious or fatal injury. Make sure that the cutting attachment is properly tightened. Use the wrench supplied or one of sufficient length to obtain the proper torque. If the head loosens after being properly tightened, stop work immediately. The retaining nut may be worn or damaged and should be replaced. If the blade or head continues to loosen, see your STIHL dealer. Never use a trimmer with a loose cutting attachment.

WARNING

Replace a cracked, damaged or wornout head or a cracked, bent, warped, damaged, dull or worn out blade immediately, even if damage is limited to superficial cracks. Such attachments may shatter at high speed and cause serious or fatal injury.

WARNING

Some STIHL mowing heads have a metal core. High-speed contact with rock or other hard objects may create sparks, which can ignite flammable materials under certain circumstances. Flammable materials 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 a mowing head with a metal core around dry vegetation or brush. Contact your local fire authorities or the U.S. Forest Service if you have any question about whether vegetation and weather conditions are suitable for the use of a mowing head with a metal core. STIHL does not recommend using a mowing head with a metal core when cutting in rocky areas or in areas with debris or other objects that could create sparks.

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 sitting on concrete, metal, bare ground or solid wood (away from any combustible substances, such as dry brush, grass or wood chips.

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

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English

002BA354 KN

002BA073 KN

002BA074 KN

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.

USING THE CUTTING ATTACHMENT

For an illustration of the various cutting attachments and instructions on proper mounting see the chapter on "Mounting the Cutting Attachment" in your instruction manual.

WARNING

To reduce the risk of severe or fatal injury from blade contact and / or loss of control, never attempt to use a metal blade on this trimmer.

Using the Mowing Heads Do not use with mowing line longer than

the intended length. With a properly mounted deflector, the built-in linelimiting blade will automatically adjust the line to its proper length.

Using the unit with an overly long nylon cutting line increases the load on the engine and reduces its operating speed. This causes the clutch to slip continuously and results in overheating

and damage to important components (e.g. clutch, polymer housing components). Such damage could, among other things, cause the cutting attachment to rotate at idle.

Mowing heads are to be used only on trimmers equipped with a line-limiting blade in the deflector in order to keep the line at the proper length (see "Main Parts" chapter in your instruction manual).

If the lawn edges are planted with trees or bordered by a fence etc., it is best to use a nylon line head. It achieves a "softer" cut with less risk of damaging tree bark etc. than polymer blades.

However, the polymer-bladed STIHL PolyCut produces a better cut if there are no plants along the edge of the lawn. Sharpening is not necessary, and worn polymer blades are easily replaced.

WARNING

To reduce the risk of serious injury, never use wire or metal-reinforced line or other material in place of the nylon cutting lines. Pieces of wire could break off and be thrown at high speed toward the operator or bystanders.

STIHL AutoCut mowing head Nylon cutting cord advances

automatically when tapped against the ground (TapAction).

STIHL PolyCut mowing head Uses nonrigid, pivoting polymer blades.

Do not continue using the PolyCut if one of the circular holes (1; arrow) becomes visible or if the projecting rim (2; arrow) has worn away. Install a new mowing head.

WARNING

To reduce the risk of accidents from shattered blades, avoid contact with stones, metal and similar solid objects. Check PolyCut blades for cracks at regular intervals. If a crack is found on one blade, always replace all blades.

STIHL FixCut mowing head Uses pre-cut lengths of nylon line.

FS 40, FS 40 C, FS 50, FS 50 C

English

Observe wear indicators.

Do not continue using the mowing head if the raised moldings (1) on the base are missing or worn – see right illustration above. The mowing head may otherwise shatter and flying objects could result in injury to the operator or bystanders. Install a new mowing head.

MAINTENANCE, REPAIR AND STORING

Maintenance, replacement, or repair of the emission control devices and systems may be performed by any nonroad engine repair establishment or individual. However, if you make a warranty claim for a component which has not been serviced or maintained properly, STIHL may deny coverage.

WARNING

Use only identical STIHL replacement parts for maintenance and repair. Use of non-STIHL parts may cause serious or fatal injury.

Strictly follow the maintenance and repair instructions in the appropriate sections of your instruction manual.

WARNING

Always stop the engine and make sure that the cutting attachment is stopped before doing any maintenance or repair work or cleaning the power tool. Do not attempt any maintenance or repair work not described in your instruction manual. Have such work performed by your STIHL servicing dealer only.

WARNING

Use the specified spark plug, and make sure it and the ignition lead are always clean and in good condition. Always press the spark plug boot snugly onto the spark plug terminal of the proper size. (Note: If the terminal has a detachable SAE adapter nut, it must be securely attached). A loose connection between the spark plug and the ignition wire connector in the boot may create arcing that could ignite combustible fumes and cause a fire.

WARNING

Never test the ignition systemby pulling the starter rope with the spark plug boot removed from the spark plug or with a removed spark plug, since the ignition is normally in the "on" position and there is a risk that uncontained sparking may cause a fire.

WARNING

Do not operate your power tool if the muffler is damaged, missing or modified. An improperly maintained muffler will increase the risk of fire and hearing loss. Your muffler is equipped with a sparkarresting screen to reduce the risk of

fire; never operate your power tool if the screen is missing, damaged or clogged. Remember that the risk of a brush or forest fire is greater in hot or dry weather.

In California, it is a violation of § 4442 or

§ 4443 of the Public Resources Code to use or operate gasoline-powered tools on forest-covered, brush-covered or grass-covered land unless the engine’s exhaust system is equipped with a complying spark arrester that is maintained in effective working order. The owner/operator of this product is responsible for properly maintaining the spark arrester. Other states or governmental entities/agencies, such as the U.S. Forest Service, may have similar requirements. Contact your local fire agency or forest service for the laws or regulations relating to fire protection requirements.

WARNING

Never repair damaged or broken heads. This may cause parts of the cutting attachment to come off and result in serious or fatal injuries.

Tighten all nuts, bolts and screws, except the carburetor adjustment screws, after each use.

Do not clean your machine with a pressure washer. The solid jet of water may damage parts of the machine.

Store the power tool in a dry and high or locked location out of reach of children.

Before storing for longer than a few days, always empty the fuel tank. See chapter "Storing the Machine" in the instruction manual.

FS 40, FS 40 C, FS 50, FS 50 C

Approved Combinations of Cutting Attachment, Deflector, Handle and Harness

0000-GXX-0401-A4

Cutting Attachment Deflector Handle Harness

English

Approved Combinations

The complete combination includes:

– Cutting attachment – Deflector – Handle – Harness

Select correct combination from the table according to the cutting attachment you intend to use.

WARNING

To reduce the risk of injury, no other combinations are permitted.

Cutting Attachments

Mowing heads 1 STIHL AutoCut C 6-2

2 STIHL DuroCut 5-2 3 STIHL PolyCut 7-3

4 STIHL PolyCut 6-2

Deflector

5 Deflector with blade, for mowing

heads

Handle

6 Loop handle

Harness

7 Shoulder strap may be used

WARNING

Based on the cutting attachment being used:

Choose the proper deflector in order to reduce the risk of injury from thrown objects and contact with the cutting attachment.

Make sure your unit is equipped with the proper handle and harness in order to reduce the risk of injury from loss of control and contact with the cutting attachment.

Do not use rigid polymer blades, metal cutting attachments or circular saw blades on this unit.

Only mowing heads may be used on loop-handled trimmers with a curved drive tube.

FS 40, FS 40 C, FS 50, FS 50 C

English

546BA003 KN

545BA004 KN

546BA004 KN

232BA066 KN

546BA005 KN

Mounting the Loop Handle

Your new power tool comes with the loop handle mounted on the drive tube, but it must be turned and lined up to suit your requirements.

Adjusting the loop handle

Versions with screw (FS 40) N Use a screwdriver or the

combination wrench to loosen the screw (1) on the handle.

Versions with star knob (FS 50) N Loosen the star knob (2) on the

handle.

All versions

Mounting the Deflector

The loop handle can be adjusted to suit the height and reach of the operator and the application by changing distance (A).

Recommended distance (A): about 6 in (15 cm)

N Slide the handle to the required

position.

N Tighten down the screw or star knob

so that the handle cannot be rotated on the drive tube.

N Push the deflector (1) over the

clamp (2) as far as stop.

N Insert the nut (3) in the hex recess in

the deflector – make sure the holes line up.

N Insert the screw (4) with washer and

tighten it down firmly.

N Turn the handle to the vertical

position.

FS 40, FS 40 C, FS 50, FS 50 C

English

546BA016 KN

232BA033 KN

546BA017 KN

Mounting the Cutting Attachment

Placing power tool on the ground

N Switch off the engine. N Lay your trimmer on its back with

the loop handle and shroud pointing down and the output shaft facing up.

Thrust Plate

The thrust plate (1) is shipped with the DuroCut 5-2 and PolyCut 6-3. It is only required for these mowing heads.

STIHL AutoCut 5-2 mowing head, STIHL AutoCut C 5-2 mowing head

N Pull the thrust plate (1), if fitted, off

the shaft (2).

STIHL PolyCut 5-2 mowing head, STIHL FixCut 6-3 mowing head

N Slip the thrust plate (1) over the

shaft (2) and engage the hex recess (3) on the external hexagon (4).

Blocking the Shaft

N To block the shaft, insert a suitable

tool (5) through the holes (6) in the deflector and thrust plate – turn the thrust plate back and forth if necessary.

Fitting the mowing head with screw mounting

Keep the supplement sheet for the mowing head in a safe place.

FS 40, FS 40 C, FS 50, FS 50 C

English

002BA385 KN

681BA019 KN

N Fit the thrust plate N Turn the mowing head

anticlockwise on the shaft (1) as far as it will go

N Retain the shaft N Tighten the mowing head

NOTICE

Remove the tool that was used to block the shaft.

STIHL AutoCut C 6-2

N Place the mowing head (2) on the

shaft (3) while inserting the internal hexagon (2) on the hexagon (4)

N Hold the mowing head (2) with your

hand.

N Turn cap (1) clockwise and tighten it

firmly by hand.

STIHL PolyCut 6-2, PolyCut 7-3

0000-GXX-3937-A0

N Push thrust plate onto the shaft N Insert the nut (10) into the mowing

head

N Turn the mowing head (11)

clockwise until it engages the shaft (5)

N Retaining the Shaft N Tighten the mowing head

Removing the Mowing Head

N Retain the shaft N Turn the mowing head clockwise

Fitting Mowing Head without Screw Mounting

Keep the supplement sheet for the mowing head in a safe place!

WARNING

Nuts that move too easily must be replaced.

NOTICE

Remove the tool that was used to block the shaft.

FS 40, FS 40 C, FS 50, FS 50 C

English

Removing the Mowing Head

STIHL AutoCut

N Hold the spool housing steady N Unscrew the cap counterclockwise.

STIHL PolyCut

N Retaining the Shaft N Turn the mowing head

counterclockwise

Fuel

This engine is certified to operate on unleaded gasoline and the STIHL twostroke engine oil at a mix ratio of 50:1.

Your engine requires a mixture of highquality gasoline and two-stroke air cooled engine oil.

Use mid-grade unleaded gasoline with a minimum octane rating of 89 ((R+M)/2) and no more than 10% ethanol content.

NOTICE

Fuel with an octane rating below 89 may increase engine temperatures. This, in turn, increases the risk of piston seizure and damage to the engine.

The chemical composition of the fuel is also important. Some fuel additives not only detrimentally affect elastomers (carburetor diaphragms, oil seals, fuel lines, etc.), but magnesium castings and catalytic converters as well. This could cause running problems or damage the engine. For this reason STIHL recommends that you use only quality unleaded gasoline!

NOTICE

Gasoline with an ethanol content of more than 10% can cause running problems and major damage in engines and should not be used.

For further details, see www.STIHLusa.com/ethanol

The ethanol content in gasoline affects engine speed – it may be necessary to readjust the carburetor if you use fuels with various ethanol contents.

WARNING

To reduce the risk of personal injury from loss of control and/or contact with the running cutting tool, do not use your unit with an incorrect idle adjustment. At correct idle speed, the cutting tool should not move.

If your machine’s idle speed is incorrectly adjusted, have your authorized STIHL servicing dealer check your machine and make the proper adjustments and repairs.

The idle speed and maximum speed of the engine change if you switch from a fuel with a certain ethanol content to a fuel with a much higher or lower ethanol content.

This problem can be avoided by always using fuel with the same ethanol content.

To ensure the maximum performance of your STIHL engine, use a high quality 2cycle engine oil. To help your engine run cleaner and reduce harmful carbon deposits, STIHL recommends using STIHL HP Ultra 2-cycle engine oil or ask your dealer for an equivalent fully synthetic 2-cycle engine oil.

To meet the requirements of EPA and CARB we recommend to use STIHL HP Ultra oil.

STIHL MotoMix

STIHL recommends the use of STIHL MotoMix. STIHL MotoMix has a high octane rating and ensures that you always use the right gasoline/oil mix ratio.

FS 40, FS 40 C, FS 50, FS 50 C

English

STIHL MotoMix uses STIHL HP Ultra two-stroke engine oil suited for high performance engines.

For further details, see www.STIHLusa.com/ethanol

If not using MotoMix, use only STIHL two-stroke engine oil or equivalent highquality two-stroke engine oils that are designed for use in air cooled two-cycle engines.

The use of non-seasonal gasoline blends may increase the potential for pressure to build in the fuel tank during operation. For example, using a winter blend during the summer will increase pressure in the fuel tank. Always use gasoline blends appropriate to the season, altitude and other environmental factors.

Do not use NMMA or TCW rated (twostroke water cooled) mix oils or other mix oils that state they are for use in both water cooled and air cooled engines (e.g., outboard motors, snowmobiles, chain saws, mopeds, etc.).

WARNING

Take care when handling gasoline. Avoid direct contact with the skin and avoid inhaling fuel vapor. When filling at the pump, first remove the container from your vehicle and place the container on the ground before filling. To reduce the risk of sparks from static discharge and resulting fire and/or explosion, do not fill fuel containers that are sitting in or on a vehicle or trailer.

The container should be kept tightly closed in order to limit the amount of moisture that gets into the mixture.

The machine's fuel tank should be cleaned as necessary.

Fuel mix ages

If not using MotoMix, only mix sufficient fuel for a few days of work, not to exceed 30 days of storage. Store in approved fuel-containers only. When mixing, pour oil into the container first, and then add gasoline. Close the container and shake it by hand to ensure proper mix of oil and gasoline.

WARNING

Shaking fuel can cause pressure to build in the fuel container. To reduce the risk of fire and severe personal injury or property damage from fuel spraying, allow the fuel container to sit for several minutes before opening. Open the container slowly to release any residual pressures. Never open the fuel container in the vicinity of any ignition source. Read and follow all warnings and instructions that accompany your fuel container.

Gaso line

US gal. US fl.oz.

12.6 2 1/2 6.4 5 12.8

Dispose of empty mixing-oil containers only at authorized disposal locations.

Oil (STIHL 50:1 or equiva lent high-quality oils)

Fueling

WARNING

Removing the cap on a pressurized fuel tank can result in gasoline, vapors and fumes being forcefully sprayed out from the tank in all directions. The escaping gasoline, vapors or fumes, sometimes referred to as fuel spraying or "geysering," can cause serious personal injury, including fire and burn injury, or property damage.

Fuel spraying can occur when the engine is hot and the tank is opened while under pressure. It can occur in hot environments even if the engine has not been running. Spraying is more likely to occur when the fuel tank is half full or more.

Avoid Injuries from Fuel Spraying. Always follow the fueling instructions in

this manual: – Treat every fuel tank as if it is

pressurized, particularly if it is half full or more.

– Always allow the power tool to cool

adequately before attempting to open the fuel tank or refueling; this will take longer in hot conditions.

FS 40, FS 40 C, FS 50, FS 50 C

English

547BA045 KN

002BA447 KN

002BA448 KN

– Never remove the cap by turning it

directly to the open position. Turn it first approximately 1/2 of a turn counter-clockwise to relieve any residual pressure.

– Never open the fuel tank while the

engine is still hot or running.

– Never open the fuel tank or re-fuel

the power tool near any sparks, flames or other ignition sources.

– Pick the right fuel: use only good

quality (89 octane or higher), fresh fuel blended for the season.

– Vapor lock: do not remove the fuel

cap in an effort to relieve vapor lock. Removing the cap has no effect on vapor lock.

– Be aware that fuel spraying is more

likely at higher altitudes.

Preparations

N Before fueling, clean the filler cap

and the area around it to ensure that no dirt falls into the tank.

N Position the machine so that the

filler cap is facing up.

WARNING

In order to reduce the risk of fire and other personal injury from escaping gas vapor and fumes, remove the fuel filler cap slowly and carefully so as to allow any pressure build-up in the tank to release slowly.

Opening

WARNING

After allowing the power tool to cool, remove the fuel filler cap slowly and carefully to allow any remaining pressure build-up in the tank to release:

N While maintaining steady,

downward pressure, slowly turn the cap approximately a 1/2 turn counter-clockwise.

N If any significant venting occurs,

immediately re-seal the tank by turning the cap clockwise to the closed position. Allow the power tool to cool further before attempting to open the tank.

N Turn the cap to the open position

only after the contents of the tank are no longer under pressure.

N Remove the fuel filler cap.

WARNING

Never remove the cap by turning it directly to the open position. First allow the power tool to cool adequately and then release any residual pressure by slowly turning the cap approximately 1/2 turn counter-clockwise. Never attempt to remove the cap while the engine is still hot or running.

Refueling

Take care not to spill fuel while fueling and do not overfill the tank – leave approximately 1/2" (13 mm) air space.

Closing

WARNING

An improperly tightened fuel filler cap can loosen or come off and spill quantities of fuel. To reduce the risk of fuel spillage and fire from an improperly installed fuel cap, tighten the fuel filler cap by hand with as much force as possible:

FS 40, FS 40 C, FS 50, FS 50 C

English

546BA007 KN

547BA015 KN

547BA016 KN

547BA017 KN

N If your fuel cap still does not tighten

properly, it may be damaged or broken. Stop using the power tool and take it to your authorized STIHL dealer for repair or replacement.

Starting / Stopping the Engine

Controls

Version with loop handle

1 Throttle trigger lockout 2 Throttle trigger 3 Stop switch with Run and 0 = Stop

positions.

Starting the Engine

N Press the manual fuel pump

bulb (4) at least five times – even if the bulb is filled with fuel.

Cold engine (cold start)

N Press in the choke lever (5) and turn

it to g at the same time.

Warm engine (warm start)

Function of stop switch and ignition system

The stop switch is normally in the Run position, i.e. when it is not depressed: The ignition is switched on – the engine is ready to start. If the stop switch is moved to the 0 position, the ignition is switched off. The ignition is switched on again automatically after the engine stops.

N Press in the choke lever (5) and turn

it to < at the same time.

FS 40, FS 40 C, FS 50, FS 50 C

English

547BA018 KN

547BA020 KN

547BA021 KN

Also use this setting if the engine has been running but is still cold.

Cranking

N Place the unit on the ground: It must

rest securely on the engine support and the deflector. Check that the cutting attachment is not touching the ground or any other obstacles.

N Make sure you have a safe and

secure footing.

N Hold the unit firmly on the ground

with your left hand and press down – do not touch the throttle trigger or lockout lever.

NOTICE

Do not stand or kneel on the drive tube.

N Hold the starter grip with your right

hand.

Version without Easy2Start N Pull the starter grip slowly until you

feel it engage and then give it a brisk strong pull.

Version with Easy2Start N Pull the starter grip steadily.

NOTICE

Do not pull out the starter rope all the way – it might otherwise break.

N Do not let the starter grip snap back.

Guide it slowly back into the housing so that the starter rope can rewind properly.

N Continue cranking until the engine

runs.

As soon as the engine runs

N Press down the throttle trigger

lockout and open the throttle – the choke lever moves to the run position F. After a cold start, warm up the engine by opening the throttle several times.

WARNING

Make sure the carburetor is correctly adjusted. The cutting attachment must not rotate when the engine is idling.

Your machine is now ready for operation.

Stopping the Engine

N Move the stop switch in the direction

of 0 – the engine stops – release the stop switch – it springs back to the run position.

Other Hints on Starting

Engine stalls in cold start position g or under acceleration

N Move the choke lever to < and

continue cranking until the engine runs.

FS 40, FS 40 C, FS 50, FS 50 C

English

547BA022 KN

Engine does not start in warm start position <

N Move the choke lever to g and

continue cranking until the engine runs.

If the engine does not start

N Check that all settings are correct. N Check that there is fuel in the tank

and refuel if necessary.

N Check that the spark plug boot is

properly connected.

N Repeat the starting procedure. Engine is flooded N Move the choke lever to F and

continue cranking until the engine runs.

Fuel tank run until completely dry N After refueling, press the manual

fuel pump bulb at least five times – even if the bulb is filled with fuel.

N Set the choke lever to suit the

engine temperature.

N Now start the engine.

Operating Instructions Cleaning the Air Filter

During break-in period

A factory-new machine should not be run at high revs (full throttle off load) for the first three tank fillings. This avoids unnecessary high loads during the break-in period. As all moving parts have to bed in during the break-in period, the frictional resistances in the engine are greater during this period. The engine develops its maximum power after about 5 to 15 tank fillings.

During Operation

After a long period of full throttle operation, allow the engine to run for a short while at idle speed so that engine heat can be dissipated by the flow of cooling air. This protects enginemounted components (ignition, carburetor) from thermal overload.

After Finishing Work

If there is a noticeable loss of engine power

N Move the choke lever (1) to <. N Turn the screw (2) in the filter

cover (3) counterclockwise until the cover is loose.

N Ease the filter cover (3) over the

choke lever and lift it away.

N Clean away loose dirt from around

the filter.

Storing for a short period: Wait for the engine to cool down. Empty the fuel tank and keep the machine in a dry place, well away from sources of ignition, until you need it again. For longer out-ofservice periods – see "Storing the Machine".

FS 40, FS 40 C, FS 50, FS 50 C

N Reach into the recess (4) in the filter

547BA023 KN

0815BA006 KN

housing and take out the felt filter (5).

N Fit a new felt filter element (5). As a

temporary measure you can knock it out on the palm of your hand or blow it out with compressed air. Do not wash.

NOTICE

Replace damaged parts. N Fit the felt filter (5) in the filter

housing, make sure it is properly seated – the arrow points to the recess.

N Move the choke lever (1) to <. N Fit the filter cover in position,

making sure the screw is square. Tighten down the screw.

English

Engine Management Adjusting the Carburetor

Exhaust emissions are controlled by the design of the engine and components (e.g. carburation, ignition, timing and valve or port timing).

The carburetor has been set at the factory to provide an optimum fuel-air mixture under most operating conditions.

Adjusting Idle Speed

Engine stops while idling N Warm up the engine for about

3 minutes.

N Turn the idle speed screw (LA)

slowly clockwise until the engine runs smoothly – the cutting attachment must not run.

Cutting attachment runs when engine is idling

N Turn the idle speed screw (LA)

counterclockwise until the cutting attachment stops moving and then rotate the screw another 1/2 to 3/4 turn in the same direction.

FS 40, FS 40 C, FS 50, FS 50 C

WARNING

If the cutting attachment continues to run when the engine is idling, have your machine checked and repaired by your servicing dealer.

English

547BA041 KN

000BA039 KN

0000-GXX-1830-A0

Spark Plug

If there is a loss of engine power, the machine is difficult to start or runs poorly at idle, first check the spark plug.

Install a new spark plug after approximately 100 operating hours or earlier if the electrodes are eroded/corroded.

The 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 degrade performance.

Removing the Spark Plug

N Shut off the engine.

N Remove the spark plug boot (1). N Unscrew the spark plug (2).

Checking the spark plug

N Clean the spark plug if it is dirty N Check the electrode gap (A) and

readjust if necessary – see "Specifications"

N Use only resistor type spark plugs of

the approved range. See the chapter "Specifications" in this instruction manual

Correct the problems that have caused fouling of the spark plug:

– too much oil in fuel mix; – dirty air filter; or – unfavorable running conditions, e.g.

operating at part throttle.

WARNING

To reduce the risk of fire and burn injury, use only spark plugs authorized by STIHL. Always press the spark plug boot (1) firmly and securely onto the spark plug terminal (2).

Do not use a spark plug with a detachable SAE adapter terminal (3). Arcing may occur that could ignite combustible fumes and cause a fire. This can result in serious injuries or damage to property.

N Only use resistor type spark plugs

with solid, non-threaded terminals

Installing the Spark Plug

N Screw the spark plug into the

cylinder.

N Press the boot firmly onto the spark

plug.

FS 40, FS 40 C, FS 50, FS 50 C

+ 64 hidden pages

Stihl FS 40, FS 50 Instruction Manual

Specifications and Main Features

Frequently Asked Questions

User Manual