STIHL HS 72 Hedge Trimmer Instruction Manual

: June 15, 2024
: STIHL

STIHL HS 72 Hedge Trimmer

HS-72-Hedge-Trimmer-product

Parts and Controls

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Front Handle (handle bar)
Spark Plug Terminal
Starting Lock
Fuel Filler Cap
Rear Handle
Cutter Blade
Cutter Blade Guard
Shroud
Choke Lever
Filter Housing
Carburetor Adjustment Screws
Starter Grip
Slide Control
Fuel Tank
Guard Muffler
Throttle Trigger
Throttle Trigger Interlock
Rear Handle Twist Lock (only HS 74)
Cutter Guard
Fuel Pump

This manual contains warnings, operating and safety precautions for the STIHL HS 72, HS 74 hedge trimmers. Pay special attention to the safety precautions outlined on pages 4 to 10. Allow only persons who understand this manual to operate your hedge trimmer. To receive maximum performance and satisfaction from your STIHL hedge trim– mer, it is important that you read and un- derstand the maintenance and safety precautions before using your hedge trimmer. Contact your STIHL dealer or the STIHL distributor for your area if you do not understand any of the instructions in this manual.

Warring
Because a hedge 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.

STIHL’s philosophy is to continually

improve all of its products. As a result, engineering changes and improvements are made from time to time. If the opera- ting characteristics or the appearance of your hedge trimmer differs from those described in this manual, please contact your STIHL dealer for information and assistance.

Front Handle (handle bar)
Spark Plug Terminal
Starting Lock
Fuel Filler Cap
Rear Handle
Cutter Blade
Cutter Blade
Guard Shroud
Choke Lever
Cutter Blade
Guard Shroud
Choke Lever
Fuel Tank
Guard Muffler
Throttle Trigger
Throttle
Trigger Interlock
Rear Handle
Twist Lock (only HS 74) 19 = Cutter
Guard = Fuel Pump

Definitions

Front Handle.
Handle bar for the left hand at front of hedge trimmer.
Spark Plug Terminal.
Connects the spark plug with the
ignition wire.
Starting Lock.
Helps to prevent movement of cutter blade during starting.
Fuel Filler Cap.
For closing the fuel tank.
Rear Handle.
The support handle for the right hand, located at or toward the rear of the hedge trimmer.
Cutter Blade.
Steel blades for cutting hedges and shrubs.
Cutter Blade Guard.
Covers cutter blade when hedge trim-mer is not in use.
Shroud.
Polymer housing which encloses the power unit.
Choke Lever.
Eases engine starting by enriching mixture.
Filter Housing.
Housing, which covers the air filter.
Caburetor
Adjustment Screws. for tuning carburetor
Starter Grip.
The grip of the pull starter, which is the device to start the engine.
Slide Control.
Lever for starting throttle and stop switch.
Fuel Tank.
For gasoline and oil mixture.
Muffler Guard.
Reduces the risk of contact with (hot) muffler.
Throttle Trigger.
Controls the speed of the engine.
Throttle Trigger Interlock.
Must be depressed before activating the throttle trigger.
Rear Handle Twist lock. {only HS 74).
Lever for rotating the rear handle.
Cutter Guard.
Helps to reduce the risk of operator contact by the cutter blade ..
Fuel Pump.
Provides additional fuel feed for a cold start.

Safety Precaution Working Techniques

Warning
Because a hedge 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 owner’s manual and the safety instructions periodically Careless or improper use of any hedge trimmer may cause serious or fatal injury.
Have your STIHL dealer show you how to operate your hedge trimmer. Observe all applicable local safety regulations, standards and ordinances.

Warning!

The use of any hedge trimmer may be hazardous. If the cutting tool comes in contact with your body, it will cut you. Striking solid foreign objects such as stones, fence wire or metal could damage the cutting attachment and may cause blades to crack, chip or break.
STIHL does not recommend the use of hedge trimmers when cutting in areas where the blades could contact such objects.
Minors should never be allowed to use a hedge trimmer. Bystanders, especially children, and animals should not be allowed in the area where a hedge trimmer is in use.
The operator is responsible for avoiding injury of third parties and damage to their property.
Never let the hedge trimmer run unattended.

Warn ing

Do not lend or rent your hedge trimmer without the owner’s manual. Be sure that anyone using your hedge trimmer understands the information contained in this manual.

Most of these safety precautions and warnings apply to the use of all STIHL hedge trimmers. Different models may have different parts and controls. See the appropriate section of your owner’s manual for a description of the controls and function of the parts of your model hedge trimmer.
Safe use of a hedge trimmer involves.

the operator
the hedge trimmer
the use of the hedge trimmer.

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 a hedge trimmer when you are fatigued Be alert -if you get tired while operating your hedge trimmer, take a break.
Tiredness may result in loss of control. Working with any hedge trimmer can be strenuous. If you have any condition that might be aggravated by strenuous work, check with your doctor before operating a hedge trimmer.
Prolonged use of a hedge trimmer (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.
Warning
Antivibration systems do not guarantee that you will not sustain whitefinger disease or carpal tunnel syndrome.
Therefore, continual and regular users should monitor closely the condition of their hands and fingers. If any of the above symptoms appear, seek medical advice immediately.

Proper Clothing

Hedge trimmer operation can cause serious injury to eyes, ears and person.
Therefore, to reduce the risk of injury to your eyes never operate a hedge trimmer unless wearing goggles or properly fitted safety glasses with adequate top and side protection complying with ANSI Z 87.1 (or your applicable national standard).
To reduce the risk of injury to your face STIHL recommends that you also weara face shield or face screen over your goggles or safety glasses.
Hedge trimmer 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.
Wear proper protective clothing.
Protect your hands with gloves when handling the hedge trimmer and the cutting tool. Heavy-duty, nonslip gloves improve your grip and help to protect your hands.
Clothing must be sturdy and snug-fitting, but allow complete freedom of movement. Avoid loose-fitting jackets, scarfs, neckties, jewelry, flared or cuffed pants, unconfined long hair or anything that could become caught on branches, brush or moving parts of the unit. Wear long pants made of heavy material to protect your legs.
Do not wear shorts.
Good footing is most important in hedge trimmer work. Wear sturdy boots with nonslip soles. Steel-toed safety boots are recommended.
Wear an approved safety hard hat to reduce the risk of injury to your head when there is a danger of head injuries.

THE HEDGE TRIMMER

For illustrtions and definitions of the hedge trimmer parts see the chapter on “Parts and Controls.

Warning!

Never modify a hedge trimmer in any way. Only attachments supplied by STIHL or expressly approved by STIHL for use with the specific STIHL hedge trimmer models are authorized. Although certain unauthorized attachments are useable for the STIHL hedge trimmer,
their use may, in fact, be extremely dangerous.

THE USE OF THE HEDGE TRIMMER

Transporting the hedge trimmer Warning!

To reduce the risk of injury from blade contact, never carry or transport the hedge trimmer with the cutter blades running The correct engine idle speed is important in this respect. If the carburetor setting is correct, the cutter blades will be stationary at idle speed. Always engage the starting lock before transporting the machine (see chapter “Star ting”). The starting lock may only be engaged when the cutter blades are at a standstill
The hedge trimmer may be carried only in the normal upright position. Grip the front handle and keep the cutter blades behind you.
Always switch off the engine and fit the scabbard over the cutter blades before transporting the hedge trimmer over long distances.
When transporting your hedge trimmer in a vehicle, properly secure it to prevent turnover, fuel spillage and damage to the hedge trimmer.

Preparation for the use of the hedge trimmer

Warning
Always check your hedge trimmer for proper condition and operation before starting, particularly the throttle trigger, throttle trigger interlock, stop switch, cutting tool and starting lock. The throttle trigger must move freely and always spring back to the idle position.The cutting tool must be properly tightened and in safe operating condition. Inspect for loose parts (nuts, screws, etc.) and for cracked, bent, warped or damaged blades. Regularly check the condition and tightness of the cutter blades – with the engine stopped! Service damaged cutter blades before using the hedge
trimmer Always keep blades sharp trimmer. Always keep blades sharp. Keep the handles clean and dry at all times; it is particularly important to keep them free of oil and resin to ensure that you can always maintain a firm grip and safely control your machine.

Warning

Removal of safety devices can lead to serious injury.
Always spray the cutter blades with STIHL resin solvent before starting work.
with the engine stopped! You can obtain this protective spray from your dealer. Apply generously.

Fueling

Your STIHL hedge trimmer uses an oil gasoline mixture for fuel (see the chapter on “Fuel” of your owner’s manual).

Warning

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

Fueling Instructions

Fuel your hedge trimmer in well ventilated areas, outdoors.

Warning

Gasoline vapor pressure may build up inside the gas tank of a two cycle engine depending on the fuel used, the weather conditions, and the venting system of the tank. In order to reduce the risk of burns or other personal injury from escaping gas vapor and fumes, remove the fuel filler cap on your hedge trimmer carefully so as to allow any pressure build-up in the tank to release slowly. Never remove fuel filler cap while 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 hedge trimmer and check for leakage.
Check for fuel leakage while refueling and during operation. If fuel leakage is found, do not start or run the engine until leak is fixed and spilled fuel has been wiped away. Take care not to get fuel on your clothing. If this happens, change your clothing immediately. Never attempt to fuel a running or hot engine.

Warning!
Unit vibrations can cause an improperly tightened fuel cap to loosen or come off and spill quantities of fuel.

In order to reduce risk of fuel spillage and fire, tighten fuel cap by hand with as much force as possible. The screw driver end of the STIHL combination wrench or other similar tool can be used as an aid in tightening slotted fuel caps.

Starting
Warning

Your hedge trimmer is a one- person machine. Start and operate your hedge trimmer without assistance.

Warning

To reduce the risk of injury from blade contact, do not attempt to “drop start” your hedge trimmer. For specific starting instructions, see the appropriate section of your manual. Place the hedge trimmer on firm ground or other solid surface in an open area. Maintain a good balance and secure footing. To reduce the risk of injury from blade contact or loss of control always engage the starting lock before starting.
When the engine starts at starting throttle, engine speed will be fast enough for the clutch to engage and move the cutting tool.
When you pull the starter grip, don’t wrap the starter rope around your hand.
Do not allow the grip to snap back, but guide the starter rope to rewind properly.
Failure to follow this procedure may result in injury to hand or fingers and may damage the starter mechanism

Working Conditions

Warning

To reduce the risk of injury from inhaltion of poisonous fumes, operate and start your hedge trimmer only outdoors in a ventilated area. Hold your hedge trimmer in such a way that you do not breathe in the exaust fumes. Operate the hedge trimmer under good visibility and daylight conditions only.
Work carefully. Take particular care in slippery conditions and on slopes.
Be careful on un-even ground. Watch out for stumps, roots, ditches or holes which could cause you to trip or stumble.
Before you start work, examine the hedge area for stones, fence wire, metal or other solid objects which could damage the cutter blades.

Operating instructions

Do not cut any material other than hedges and shrubs. The cutting tools may be used only for the operations described in your manual.

Warning

To reduce the risk of injury from loss of control, always hold your hedge trimmer firmly with both hands while you are working. Your right hand should grip the rear handle.
This also applies to left-handers.
Wrap your fingers tightly around the front and rear handles.

Warning

Never attempt to operate any hedge trimmer with one hand. Loss of control of the hedge trimmer resulting in serious or fatal injury may result.

Make sure you always have good footing. Always work calmly and carefully, stay alert so as not to endanger others.

When working close to the ground, make sure that no sand, grit or stones get between the cutter blades. If the cutter blades become jammed by thick branches or any other obstruction, switch off the engine immediately before attempting to free the blades.

Warning
To reduce the risk of injury from loss of control, never work on a ladder, in a tree or any other insecure support. Never use the hedge trimmer above shoulder height or with one hand.

Warning
The cutter blades tend to run on for a short period after the throttle trigger is released (flywheel effect).

Warning

To reduce the risk of injury from loss of control, always hold your hedge trimmer firmly with both hands while you are working. Your right hand should grip the rear handle.
This also applies to left-handers.
Wrap your fingers tightly around the front and rear handles.

Warning!

Never attempt to operate any hedge trimmer with one hand. Loss of control of the hedge trimmer resulting in serious or fatal injury may result.
only detrimentally affect elastomers (carburetor diaphragms, oil seals, fuel lines etc.), but magnesium castings as well. This could cause running problems or even damage the engine. For this reason it is essential that you use only name branded fuels!
Use only STIHL two-stroke engine oil or equivalent branded two-stroke air-cooled engine oils with the classification TC for mixing.
We recommend STIHL 50:1 two-stroke engine oil since it is specially formulated for use in STIHL engines. The mix ratio with STIHL oil is 50:1 (50 parts gasoline to 1 part oil), or 25:1 (25 parts gasoline to 1 part oil) with other branded two-strokeair-cooled engine oils.
Do not use BIA or TCW (two-stroke water cooled) mix oils!
Take care when handling gasoline.
Avoid direct contact with the skin and avoid inhaling fuel vapour.
The canister should be kept tightly closed in order to avoid any moisture getting into the mixture.
The fuel tank arid the canister in which fuel mix is stored should be cleaned from time to time.

Important adjustments
Warning!
To reduce the risk of personal injury from loss of control or contact with the running cutting blades, do not use a hedge trimmer with incorrect idle adjustment. At correct idle speed, the cutting blades should not move. For directions to adjust idle speed, see the appropriate section of your owner’s manual.
If you cannot set the correct idle speed, have your STIHL dealer check your hedge trimmer and make proper adjustments or repairs.

MAINTENANCE, REPAIR AND STORING

Use only STIHL replacement parts for maintenance and repair. Use of parts manufactured by others may cause serious or fatal injury. Follow the maintenance and repair instructions in the appropriate section of your owner’s manual.

Warning
Always stop the engine and make sure that the cutting tool is stopped before doing any maintenance or repair work or cleaning the hedge trimmer. Do not at- tempt any maintenance or repair work not described in your owner’s manual. Have such work performed at your STIHL service shop only.

Warning:
Never repair damaged cutting attachments by welding, straightening or modifying the shape. This may cause parts of the cutting tool to come off and result in serious or fatal injuries. Check condition of cutting tool at regular short intervals. If behavior of tool changes, check it immediately for tightness or any signs of cracks in
particular. Replace damaged or dull cutting tools immediately, even if they have only superficial cracks. Warning! To reduce the risk of fire, check fuel filler cap for leaks at regular intervals. Use the specified spark plug and make sure it and the ignition lead are always in good condition. Always clean dust and dirt off the machine after finishing work. Do not use a grease solvent for cleaning! An aerosol can of resin solvent (protective spray), Part No. 0782 420 1002, is available for spraying the cutter blades. This resin solvent protects the cutter blades and has anticorrosive properties. Spray the cutter blades before and after work. Then start and run the hedge trimmer briefly so that the resin solvent is evenly distributed over the blades. If the hedge itself is very dusty and dirty, spray the cutter blades more frequently. This greatly reduces blade friction and the damaging effects of sap and dust particles.

Warning
Do not operate your hedge trimmer if the muffler is damaged, missing or modefied. An improperly maintained muffler will increase the risk of fire and hearing loss. Never touch a hot muffler or burn will result. If your muffler was equipped with a spark-arresting screen to reduce the risk of fire (e.g. in the USA, Canada and Australia), never operate your hedge trimmer if the screen is missing or damaged. Remember that the risk of fo- rest fires is greater in hot or dry weather. Keep the engine and muffler free from cuttings, chips, leaves, fibers and excess lubricant.

Warning
In order to reduce the risk of fire, do not modify or remove any part of the muffler or spark arresting. Keep cutting tool sharp. Tighten all nuts, bolts and screws except the carburetor adjustment screws after each use.
Keep spark plug and wire connection tight and clean. The spark plug electrode gap should be checked with a feeler gauge at least every 50 operating hours and reset if necessary. Fit a new spark plug if the electrodes are badly pitted. Store hedge trimmer in a dry, high or locked location out of reach of children. Before storing for longer than a few days, always empty the fuel tank.

Fuel mix

Your two-stroke engine requires a mixture of brand-name gasoline and quality two-stroke engine oil with the classification TC. Use regular branded unleaded gasoline with a minimum octane number of 90 ROZ (U.S.A./Canada: pump octane min. 891). If the octane number of the regular grade gasoline in your area is lower use premium unleaded fuel. Fuel with a lower octane number may result in preignition (causing “pinging”) which is accompanied by an increase in engine temperature. This, in turn, increases the risk of the 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 as well. This could cause running problems or even damage the engine. For this rea- son it is essential that you use only name branded fuels! Use only STIHL two-stroke engine oil or equivalent branded two-stroke air-cooled engine oils with the classification TC for mixing. We recommend STIHL 50:1 two-stroke engine oil since it is specially formulated for use in STIHL engines. The mix ratio with STIL oil is 50:1 (50 parts gasoline to 1 part oil), or 25:1 (25 parts gasoline to 1 part oil) with other branded two-stroke- air-cooled engine oils. Do not use BIA or TCW (two-stroke water cooled) mix oils! Take care when handling gasoline. Avoid direct contact with the skin and avoid inhaling fuel vapour. The canister should be kept tightly closed in order to avoid any moisture getting into the mixture. The fuel tank and the canister in which fuel mix is stored should be cleaned from time to time.

Fuel mix ages

Only mix sufficient fuel for a few days work, not to exceed 30 days of storage. Store in approved safety fuel-canisters only.
When mixing, pour oil into the canister first, and then add gasoline.
Change the fuel pick up body every year.
Before storing your machine for a long period, drain and clean the fuel tank and run engine until carburetor is dry.
Before fueling, clean the filler cap and the area around it to ensure that no dirt falls into the tank.
Always thoroughly shake the mixture in the canister before fueling your machine.
In order to reduce the risk of burns or other personal injury from escaping gas vapor and fumes, remove the fuel filler cap carefully so as to allow any pressure build-up in the tank to release slowly.
After fueling, tighten fuel cap as securely as possible by hand.

Gaso- line| STIHL
engine oil 50:1| Other branded TC oils
25:1
---|---|---
Liters _
_1| Liters _
0.02| (cc)
_(20)| Liters _
0.04| (cc)
_(40)
5| 0.10| (100)| 0.2| (200)
10| 0.20| (200)| 0.4| (400)
---|---|---|---|---
15| 0.30| (300)| 0.6| (600)
20| 0.40| (400)| 0.8| (800)
25| 0.50| (500)| 1.0| (1000)
| | | |
Gaso- line
US gal.| STIHL
engine oil 50:1
US fl.oz| Other branded TC oils
25:1
US fl.oz
1| 2.6| 5.1
2 1/2| 6.4| 12.8
5| 12.8| 25.6

The rear handle can be turned 90 to the left or right for better control and comfort

Fueling

Change the fuel pick up body every year. Before storing your machine for a long period, drain and clean the fuel tank and run engine until carburetor is dry.

Before fueling, clean the filler cap and the area around it to ensure that no dirt falls into the tank. Always thoroughly shake the mixture in the canister before fueling your machine. In order to reduce the risk of burns or other personal injury from escaping gas vapor and fumes, remove the fuel filler cap carefully so as to allow any pressure build-up in the tank to release slowly. After fueling, tighten fuel cap as securely as possible by hand.

Rear Handle (HS 74 only)

The rear handle can be turned 90 to the left or right for better control and comfort – Let go of throttle trigger –
Do not operate the throttle while the catch is released.
Do not release the catch while you are operating the throttle.
Do not open the throttle
Release the catch (1).
Turn the handle (2) as required and allow catch to snap into position.

Make sure the handle is locked before opening the throttle.

Starting

Observe safety precautions – see chapter “Safety Precautions” in this manuaL
Before starting work, remove the cutting blade guard.
Move lever (1) of starting lock to position Squeeze the throttle trigger (2} and move the slide contro1(3) to at the same time.
Now release the throttle trigger.
Let go of the slide control = starting throttle position.

Set the choke lever (4):
for cold start to
for warm start to
( even if engine has been running but is still cold)
Press the fuel pump bulb (5) at least five times.

Put your hedge trimmer on firm ground with the starter facing up.
Make sure you have a secure footing: Hold the unit with your left hand on the front handle and press it down firmly.
Pull the starter grip slowly with your right hand until you feel it engage and then give it a brisk strong pull. Do not pull out the starter rope more than 75 cm (30″) – it might break.
Do not let the starter grip snap back guide it back into the housing slowly so that the starter rope can rewind properly.
When engine begins to fire:
Move choke lever and continue cranking – as soon as engine runs, immediately blip the throttle trigger, the slide control moves to the
“Run” position I and the engine returns to idling speed.
Move the starting lock lever to ( ) position.
To shut down the engine: Move the slide control to “O”.
At very low outside temperatures:
Allow engine to warm up.
As soon as engine runs:
Blip the throttle trigger so that slide control moves to “Run” position I and the engine returns to idling speed.
Open throttle slightly – warm up engine for short period.
If the engine doesn’t start:
If you did not move the choke lever to quickly enough after the engine began to fire, the combustion chamber has flooded. Remove spark plug terminal (7) –
Unscrew and dry off the spark plug
Set slide control to “O” –
Open the throttle fully –
Pull the starter rope several times to clear the combustion chamber.
Refit the spark plug and connect the spark plug terminal
Set slide control to I
Set choke lever to even if engine is cold
Now start the engine .
Fuel tank run dry and then refueled
Press fuel pump bulb (5) at least five times.
Now start the engine .

Cleaning the Air Filte1

If there is a noticeable loss of engine power

Move choke lever to Press in the tab (1). Ease the filter cover (2) over the tab and lift it off..
Clean away loose dirt from around the filter
Remove the foam element (3) and felt element (4).
Wash the air filter in fresh, nonflammable cleaning solution (e.g .. warm soapy water) and then dry Always replace a damaged filter element
Fit the foam element (3) in the filter cover (2).
Fit the felt element (4) in the filter base (5).
Fit the filter cover and engage it in position ..

The carburetor has been adjusted for optimum performance and fuel efficiency under the barometric pressure and climatic conditions at the factory.

Standard setting
If it is necessary to readjust the carburetor from scratch, first carry out the standard setting.

H = High speed adjusting screw: back off 1 full turn.
L = Low speed adjusting screw: back off 1 full turn.

If no tachometer is available, do not set turn the high speed adjusting screw beyond the standard setting to obtain a leaner mixture.

Operation at high altitude (mountains) or at sea level
Slight correction may be necessary.
Use a tachometer when changing setting of high speed adjusting screw (H) – do not exceed maximum permissible engine speed. Turn the high speed adjusting screw (H) one quarter turn counterclockwise (richer). Avoid risk of engine damage which can be caused by lack of lubrication and overheating
Max. engine speed: 10,500 rpm

Check cutting blades – clean if necessary (they must be clean, move freely and not be bent or twisted).
Check air filter and clean it if necessary.
Set idle speed correctly.
Warm up the engine.
Turn the high speed adjusting screw (H) and low speed adjusting screw (L) clockwise (leaner) at higher altitudes or counterclockwise (richer) at sea level.

Turn the screws very slowly and carefully – slight changes have a noticeable effect on the engine’s running behavior.

Corrections to high speed adjusting screw:
The high speed adjusting screw (H) alters the power output and maximum engine speed. If you make the setting too lean, the maximum permissible engine speed will be exceeded – this could damage the engine.

Cutting blades run when engine is idling
Turn the idle speed adjusting screw (LA) counterclockwise until cutting blades stop running at idle speed. It is usually necessary to change the setting of the low speed adjusting screw (L) after every correction at the idle speed adjusting screw (LA)

Engine stops while idling
Turn the idle speed adjusting screw (LA) clockwise until the engine runs smoothly.

Erratic idling behavior, poor acceleration
Idle setting is too lean. Turn the low speed adjusting screw (L) counterclockwise until engine runs and accelerates smoothly.

Exhaust smokes at idle speed
Idle setting is too rich. Turn the low speed adjusting screw (L) clockwise until engine speed drops. Then turn screw back one quarter turn and check that engine still accelerates smoothly when you open the throttle.

Spark Arresting Screen in Muffler

If the engine is low on power, check the spark arresting screen inside the muffler.

Remove the shroud ..
Take out the screws (1).
Remove the cover (2).
Remove the spark arresting screen (3).
Clean spark arresting screen if necessary.
If screen is damaged or coked up, fit a new one.
Refit the spark arresting screen.
Fit the cover.

If engine is down on power, difficult to start or runs poorly at idling speed, first check the spark plug.

Remove spark plug -see chapter “Starting”.
Clean dirty spark plug.
Check electrode gap –
(Af =It should be 0.05 mm (0.02″) – readjust as necessary.
Use only suppressed spark plugs of the approved type.

Rectify faults which have caused fouling of spark plug:
Incorrect carburetor setting, 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.

Let go of throttle trigger Do not open the throttle

Release the catch

Turn the handle
as required and allow catch to snap into position.

Make sure the handle is locked before opening the throttle.
Do not operate the throttle while the catch is released.
Do not release the catch while you are operating the throttle.
Observe safety precautions – see chapter “Safety Precautions” in this manuaL
Before starting work, remove the cutting blade guard. Move lever
- of starting lock to Q position Squeeze the throttle trigger
- and move the slide contro1
- to }x( at the same time.
Now release the throttle trigger.
Let go of the slide control = starting throttle position.

Set the choke lever (4}: for cold start to for warm start to ( even if engine has been running but is still cold) Press the fuel pump bulb (5) at least five times.

Put your hedge trimmer on firm ground with the starter facing up.
Make sure you have a secure footing: Hold the unit with your left hand on the front handle and press it down firmly.
Pull the starter grip slowly with your right hand until you feel it engage and then give it a brisk strong pull. Do not pull out the starter rope more than 75 cm (30″) – it might break.
Do not let the starter grip snap back
guide it back into the housing slowly so that the starter rope can rewind properly.
When engine begins to fire
Move choke lever and continue cranking – as soon as engine runs, immediately blip the throttle trigger, the slide control moves to the “Run” position I and the engine returns to idling speed.
Move the starting lock lever to (0) position.
To shut down the engine: Move the slide control to “O.
At very low outside temperatures: Allow engine to warm up.
As soon as engine runs:
Blip the throttle trigger so that slide control moves to “Run” position I and the engine returns to idling speed.
Open throttle slightly – warm up engine for short period.
If the engine doesn’t start:
If you did not move the choke lever to quickly enough after the engine began to fire, the combustion chamber has flooded.
Remove spark plug terminal (7).
Unscrew and dry off the spark plug
• Set slide control to “O”
Open the throttle fully
Pull the starter rope several times to clear the combustion chamber.
Refit the spark plug and connect the spark plug terminal
Set slide control to.
Set choke lever to even if engine is cold
Now start the engine.
Fuel tank run dry and then refueled
Press fuel pump bulb (5) at least five times.
Now start the engine .

If there is a noticeable loss of engine power.

Move choke lever to Press in the tab

Ease the filter cover
over the tab and lift it off.
Clean away loose dirt from around the filter
Remove the foam element (3) and felt element (4).
Wash the air filter in fresh, nonflammable cleaning solution (e.g .. warm soapy water) and then dry Always replace a damaged filter element
Fit the foam element (3) in the filter cover (2).
Fit the felt element (4) in the filter base (5).
Fit the filter cover and engage it in position

The carburetor has been adjusted for optimum performance and fuel efficiency under the barometric pressure and climatic conditions at the factory.

Standard setting

If it is necessary to readjust the carburetor from scratch, first carry out the standard setting.
H = High speed adjusting screw: back off 1 full turn.
L = Low speed adjusting screw

If no tachometer is available, do not set turn the high speed adjusting screw beyond the standard setting to obtain a leaner mixture.

Operation at high altitude (mountains) or at sea level

Slight correction may be necessary.
Use a tachometer when changing setting of high speed adjusting screw (H) – do not exceed maximum permissible engine speed.
Turn the high speed adjusting screw (H) one quarter turn counterclockwise (richer).
Avoid risk of engine damage which can be caused by lack of lubrication and overheating Max. engine speed: 10,500 rpm.
Check cutting blades clean if necessary (they must be clean, move freely and not be bent or twisted).
Check air filter and clean it if necessary.
Set idle speed correctly.
Warm up the engine.
Turn the high speed adjusting screw (H) and low speed adjusting screw (L) clockwise (leaner) at higher altitudes or counterclockwise (richer) at sea level.

Turn the screws very slowly and carefully – slight changes have a noticeable effect on the engine’s running behavior.

Corrections to high speed adjusting screw

The high speed adjusting screw (H) alters the power output and maximum engine speed.
If you make the setting too lean, the maximum permissible engine speed will be exceeded this could damage the engine.

Cutting blades run when engine is idling

Turn the idle speed adjusting screw (LA) counterclockwise until cutting blades stop running at idle speed.
It is usually necessary to change the setting of the low speed adjusting screw (L) after every correction at the idle speed adjusting screw (LA)

Engine stops while idling

Turn the idle speed adjusting screw (LA) clockwise until the engine runs smoothly.

Erratic idling behavior, poor acceleration

Idle setting is too lean.
Turn the low speed adjusting screw (L) counterclockwise until engine runs and accelerates smoothly.

Exhaust smokes at idle speed

Idle setting is too rich.
Turn the low speed adjusting screw (L) clockwise until engine speed drops. Then turn screw back one quarter turn and check that engine still accelerates smoothly when you open the throttle.

Spark Arresting Screen in Muffler

Checking the Spark Plug

If the engine is low on power, check the spark arresting screen inside the muffler.

Remove the shroud Take out the screws
Remove the cover
Remove the spark arresting screen

Clean spark arresting screen if necessary.
If screen is damaged or coked up, fit a new one.
Refit the spark arresting screen.
Fit the cover

If engine is down on power, difficult to start or runs poorly at idling speed, first check the spark plug.

Remove spark plug -see chapter “Starting”.
Clean dirty spark plug.
Check electrode gap (Af =It should be 0.05 mm (0.02″) readjust as necessary.
Use only suppressed spark plugs of the approved type.
Rectify faults which have caused fouling of spark plug:
Incorrect carburetor setting, 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.

Replacing the Starter Rope and Rewind Spring

Remove the screws .
Lift the starter cover
off the engine.

Remove the rope rotor very carefully – the rewind spring is seated in the rope rotor and may pop out, uncoil and cause injury if care is not taken
Remove remaining rope from rotor -thread the new rope – 0 3 mm x 900 mm – (1/8″ dia. x 35 1/2″) – through the rotor and secure
it with a simple overhand knot. Thread the other end – from inside – through the rope guide bush and the underside of the starter grip and secure with one of the special knots shown do not wind rope onto rotor.
Coat rope rotor bearing bore with non-resinous oil.
Slide rotor onto starter post – turn it back and forth until the anchor loop (6) of the spring engages.
Fit screw and tighten down firmly.

Tensioning rewind spring

Make a loop in the starter rope and use it to turn the rope rotor six full revolutions counter clockwise. Hold the rotor steady straighten the twisted rope release the rotor
let go of rope slowly so that it winds onto the rotor.
The starter grip must be firmly seated in the rope guide bush. If grip droops to one side:
Add one more turn on rope rotor to increase spring tension.
When starter rope is fully extended it must be possible to rotate the rotor another one half turn.
If this is not the case, the spring is over tensioned and could break. Take one turn of rope off the rotor.

Replacing a broken rewind spring

Lubricate the new spring with a few drops of non-resinous oil – do not open the wire retainer.
Remove the rope rotor.
Remove parts of old spring.
Fit the new spring position outer spring loop in the recess -the wire retainer slips off in this process.

If the spring pops out and uncoils: Refit it in the counterclockwise direction -start outside and work inward.

Install the rope rotor.
Tension the rewind spring.
Fit the starter cover.

Gearbox Lubrication

Use STIHL multipurpose grease 0781 120 1109/10 for lubrication of the spur gears.

Remove the filler plug from the gear box cover.
Screw the tube of grease into the filler hole.
Roll up the end of the tube to the next division on the scale. This forces about 20 g (3/4 oz) grease into the gearbox.
Relubrication the gearbox about every 25 hours of operation.

Sharpening Instructions

It is best to resharpen cutting blades with the STIHL USG universal sharpener.
It is also possible to use a portable electric grinder or a flat crosscut file.
The portable electric grinder should be a high-speed unit fitted with an 8 mm (5/16″) grinding point
Hold the file or grinding point at an angle of 45 to the cutting blade.
Always file toward the cutting edge.
The file only sharpens on the for ward stroke – lift it off the blade on the backstroke.
Remove burr from cutting edge with a whetstone.
CD Only remove as little material as possible.
Before refitting resharpened blades clean away filing or grinding dust and lubricate the blades with grease.

Working Instructions

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

After finishing work

Storing for short period -fill the fuel tank and keep the unit in a dry place until you need it again.
Storing for a long period Drain and clean the fuel tank run engine until carburetor is dry
Check tightness of nuts and screws (not adjusting screws) at regular inteNals and retighten as necessary.

Storing the machine

Remove the knives.
Drain and clean the fuel tank.
Drain the carburetor, otherwise the carburetor diaphragms may stick together!
Thoroughly clean the machine, particularly the cylinder fins and air filter!
Always store the machine in a dry, safe place where it cannot be reached by unauthorized users (e.g. children).

The user of the hedge trimmer may carry out only the maintenance operations described in this manual. Other repair work may be performed only by an authorized STIHL Service Shop.

Maintenance Chart

$STIHL -HS -72 -Hedge -Trimmer -FIG $42$$

The user of the hedge trimmer may carry out only the maintenance operations described in this manual. Other repair work may be performed only by an authorized STIHL Service Shop.
Warranty claims following repairs can be accepted only if the repair has been performed by an authorized STIHL Service Shop using original STIHL spare parts. Original STIHL parts can be identified by the STIHL part number, the STIHL” logo and the STIHL parts symbol . The symbol may appear alone on small parts.

Specifications

Engine

Single cylinder two-stroke engine
Displacement: 23.9 cm° (1.46 cu.in)
Bore: 33 mm (1.20 in)
Stroke: 28 mm (1.10 in)
Power 0.8 kW
Max. permissible engine speed: See “Adjusting the Carburetor”
Idle speed 2800 r.p.m.

Ignition System

Type: Electronic (breakerless) magneto ignition
Spark plug (suppressed): Bosch WSR 6 F or NGK BPMR 7 A; Heat range 200
Electrode gap: 0.5 mm (0.02 in)
Spark plug thread: M 14×1.25; 9.5 mm (0.37 in) long

Fuel System

Carburetor. All position dia- phragm carburetor with integral fuel pump
Air filter: Foam and felt elements
Fuel tank capacity: 0.37 L (0.78 US pt)
Fuel mixture: See chapter “Fuel Mix”
Weight:
(complete unit)
HS 72/420 5.1 kg (11.2 Ib)
HS 72/550 5.3 kg (11.7 lb)
HS 74/420 5.2 kg (11.5 lb)
HS 74/550 5.4 kg (11.9 lb)
HS 74/700* 5.6 kg (12.3 lb)

Length of the cutter blades

$STIHL -HS -72 -Hedge -Trimmer -FIG $1$$

Weighted equivalent level includes idling, full load and racing with the same duration of exposure
Length of the cutter blades 550 mm (21.7 in)

Warranty claims following repairs can be accepted only if the repair has been performed by an authorized STIHL Service Shop using original STIHL spare parts.

Certificate of conformity
This certificate of Conformity applies only in the countries of the European Union.

I, the undersigned
Andreas Stihl
Badstr. 115
D-71336 Waiblingen
certify that the new machine described below
Category: Hedge trimmer
Make: STIHL
Model: HS 72, HS 74
Serial
identification: 4226
conforms to the specifications of Directive 89/392/EEC and 89/336EEC. The product has been developed and manufactured in compliance with the following standard:
EN 774,
EN 50082,
CISPR 12
Done at Waiblingen,
July 19, 1995
ANDREAS STIHL
Steinhauser
Director Group Product Management

Quality Certification
All STIHL products comply with the highest quality standards. An independent organization has certified that all products manufactured by STIHL meet the strict requirements of the ISO 9001 standard for quality management systems in terms of product development, materials purchasing, production, assembly, documentation and customer service.

WARNING

The engine exhaust from this product contains chemicals known to the State of California to cause cancer, birthdefects or other reproductive harm.