Husqvarna HS 139A Instruction manual

Workshop manual
HS 139A, HS 166A
English
1425 - 001 - 03.06.2020

Contents
1 Introduction
1.1 General.................................................................. 3
1.2 Document description............................................ 3
1.3 Target group...........................................................3
1.4 Revisions................................................................3
1.5 Safety..................................................................... 3
1.6 Servicing tools........................................................3
2 Safety
2.1 Safety definitions....................................................4
2.2 General safety instructions.....................................4
2.3 Special safety instructions......................................4
2.4 Symbols on the product......................................... 4
3 Prepare and do servicing on the product
3.1 Maintenance schedule........................................... 6
3.2 To fill fuel................................................................6
3.3 To do a check of the oil level..................................7
3.4 To replace the engine oil........................................7
4 Servicing data
5 Function overview
5.1 Product overview..................................................13
5.2 Product overview..................................................14
5.3 Serial numbers on the product............................. 15
6 Repair instructions
6.1 To clean and examine the product parts..............16
6.2 Starter.................................................................. 16
6.3 Air filter................................................................. 20
6.4 Carburetor............................................................ 21
6.5 Carburetor............................................................ 22
6.6 Muffler.................................................................. 29
6.7 Ignition system..................................................... 30
6.8 Fuel tank.............................................................. 31
6.9 Flywheel............................................................... 33
6.10 Crankcase.......................................................... 33
6.11 Function test.......................................................37
7 Troubleshooting
7.1 Troubleshooting schedule.................................... 39
8 Technical data
8.1 Technical data......................................................41
8.2 Power speed curve.............................................. 42
8.3 Dimensions.......................................................... 43
8.4 Tightening torques............................................... 45
8.5 Standard dimensions and wear limits.................. 45
21425 - 001 - 03.06.2020

1 Introduction
1.1 General
HS 139A
HS 166A
This publication covers Husqvarna engines HS 139A,
HS 166A from model year 2020. Workshop manuals are
available for models that are no longer sold.
1.2 Document description
This manual gives a full description of how to do
maintenance and repair on the product. It also gives
safety instructions that the personnel must obey.
1.3 Target group
This manual is for personnel with a general knowledge
of how to do repair and do servicing. All personnel that
do repair or do servicing on the product must read and
understand the manual.
1.4 Revisions
Changes to the product can cause changes to the
maintenance work and spare parts. Separate
information is sent out for each change.
Read the manual together with all received information
about changes to maintenance and spare parts for the
product.
1.5 Safety
WARNING: All personnel that repair or do
servicing on the product must read and
understand the safety instructions in this
workshop manual.
1.6 Servicing tools
The servicing tools for this product are standard tools. It
is not necessary to use special Husqvarna servicing
tools. The instructions give information on which tools
that are necessary for each procedure.
1425 - 001 - 03.06.2020 Introduction - 3

2 Safety
2.1 Safety definitions
Warnings, cautions and notes are used to point out
specially important parts of the manual.
WARNING: Used if there is a risk of injury or
death for the operator or bystanders if the
instructions in the manual are not obeyed.
CAUTION: Used if there is a risk of damage to
the product, other materials or the adjacent area
if the instructions in the manual are not obeyed.
Note: Used to give more information that is necessary in
a given situation.
2.2 General safety instructions
WARNING: Read the warning instructions that
follow before you use the product.
The service center that repairs the product must have
safety devices that obey local regulations. Warnings and
cautions are used to point out specially important parts
of the workshop manual.
2.3 Special safety instructions
• Stop the engine, remove the spark plug and let the
engine become cool before maintenance.
• Do not start the product indoors or in areas that do
not have sufficient airflow. The exhaust fumes from
the engine contain carbon monoxide which is an
odorless, poisonous and very dangerous gas.
• Do not start the product near flammable materials.
The exhaust fumes from the engine are hot and can
contain sparks which can start a fire.
• Keep all body parts away from hot surfaces, or high
voltage lead.
• Do not put the product or a fuel container near warm
objects, an open flame, a spark or a pilot light.
2.3.1 Fuel safety
WARNING: Read the warning instructions that
follow before you use the product.
• Fuel is flammable and the fumes are explosive. Be
careful with fuel to prevent injury, fire and explosion.
• Do not breathe in the fuel fumes. The fuel fumes are
poisonous and can cause injury. Make sure that the
airflow is sufficient.
• Do not remove the fuel tank cap or fill the fuel tank
when the engine is on.
• Let the engine become cool before you refuel.
• Do not fill fuel in an indoor area. Not sufficient airflow
can cause injury or death because of asphyxiation or
carbon monoxide.
• Do not smoke near the fuel or the engine.
• Do not put hot objects near the fuel or the engine.
• Do not fill fuel near sparks or flames.
• Before you refuel, open the fuel tank cap slowly and
release the pressure carefully.
• Fuel on your skin can cause injury. If you get fuel on
your skin, use soap and water to remove the fuel.
• If you spill fuel on your clothing, change clothing
immediately.
• Do not fill the fuel tank fully. Heat causes the fuel to
expand. Keep a space at the top of the fuel tank.
• Tighten the fuel tank cap fully. If the fuel tank cap is
not tightened, there is a risk of fire.
• Before you start the product, move the product to a
minimum of 3 m/10 ft from where you refueled.
• Do not start the product if there is fuel or engine oil
on the product. Remove the unwanted fuel and
engine oil and let the product dry before you start
the engine.
• Examine the engine for leaks regularly. If there are
leaks in the fuel system, do not start the engine until
the leaks are repaired.
• Do not use your fingers to examine the engine for
leaks.
• Keep fuel in approved containers only.
• When the product and fuel is in storage, make sure
that fuel and fuel fumes cannot cause damage.
• Drain the fuel in an approved container outdoors and
away from sparks and flames.
2.4 Symbols on the product
WARNING! This product can be
dangerous and cause serious injury or
death to the operator or others. Be careful
and use the product correctly.
Read the operator's manual carefully and
make sure that you understand the
instructions before use.
Stop the engine and remove the ignition
cable before repairs or maintenance.
Fuel.
Oil level.
Risk of fire.
4 - Safety 1425 - 001 - 03.06.2020

Do not breathe in exhaust fumes. The
exhaust fumes from the engine contain
carbon monoxide, an odourless,
poisonous and very dangerous gas. Do
not start the engine indoors or in closed
spaces.
Hot surface.
Fill the engine with oil before
you start the product..
Note: Other symbols/decals on the product refer to
certification requirements for some commercial areas.
1425 - 001 - 03.06.2020 Safety - 5

3 Prepare and do servicing on the product
3.1 Maintenance schedule
Maintenance Before
operation Each 50 h Each 100 h
Clean the external surface. X
Clean the muffler, the exhaust pipe and the engine from dirt and unwanted lubri-
cant. X
Examine the engine, the fuel tank and the fuel lines for leaks. X
Tighten nuts and screws. X
Examine the fuel filter for contamination and the fuel hose for cracks and other
defects. Replace the parts if it is necessary. X
Do a check of the engine oil level. Fill with oil if it is necessary. X
Replace the engine oil.12 X
Examine the starter and the starter rope for damages. X
Examine the air filter. Clean or replace if it is necessary. X
Clean the air filter. Replace if it is necessary. X
Replace the air filter. X
Examine the spark plug. Clean if it is necessary. X
Replace the spark plug. X
Clean the external surface of the carburetor and the area around it. X
Clean the inner surface of the fuel tank. X
Examine the spark plug. Replace the spark plug if it is necessary. X
Do a check of all cables and connections. X
Make sure that the bevel gear is filled with grease. X
Examine the flywheel brake pad. X
Clean the spark arrestor screen (optional equipment). Replace the spark arrestor
screen if it is necessary. X
Examine the idle speed. Adjust if it is necessary. X
Examine and adjust the valve play. X
Clean the combustion chamber. X
Examine the fuel line. Replace if it is necessary. X
3.2 To fill fuel
WARNING: Gasoline is very flammable. Be
careful and refuel outdoors, refer to Fuel safety
on page 4 .
WARNING: Do not use the fuel tank as a
support area.
CAUTION: Incorrect type of fuel can result in
engine damage.
The engine runs on gasoline with a minimum octane
rating of 91 RON (87 AKI), not mixed with oil. We
recommend biodegradable alkylate gasoline. Do not use
gasoline that contains more than 10% ethanol.
• Do a check of the fuel level before each use and
refuel if it is necessary.
1Replace after first month or after 5 h of operation.
2Replace the engine oil each 25 h when used with high loads or in high ambient temperatures.
6 - Prepare and do servicing on the
product
1425 - 001 - 03.06.2020

• Do not fully fill the fuel tank. Keep a space of a
minimum 2.5 cm.
3.3 To do a check of the oil level
CAUTION: A too low oil level can do damage to
the engine. Do a check of the oil level before
you start the product.
1. Put the product on level ground.
2. Remove the oil tank cap with the attached dipstick.
3. Clean the oil from the dipstick.
4. Put the dipstick fully into the oil tank to give a correct
picture of the oil level.
5. Remove the dipstick.
6. Examine the oil level on the dipstick.
7. If the oil level is low, fill with engine oil and do a
check of the oil level again.
3.4 To replace the engine oil
WARNING: Engine oil is very hot directly after
the engine is stopped. Let the engine become
cool before you drain the engine oil. If you spill
engine oil on your skin, clean with soap and
water.
1. Drain the fuel tank. Refer to To drain the fuel tank on
page 31 .
2. Remove the ignition cable from the spark plug.
3. Put a container below the drain plug for the engine
oil.
4. Remove the oil tank cap.
5. Tilt the product and let the oil run out into the
container.
6. Fill with new engine oil of the type recommended in
Technical data on page 41 .
7. Do a check of the oil level. Refer to To do a check of
the oil level on page 7 .
1425 - 001 - 03.06.2020 Prepare and do servicing on the
product - 7

4 Servicing data
M6 x 60 (2)8~12 Nm
M6 x 14 (3)8~12 Nm
M6 (2)8~12 Nm
M66~10 Nm
HS 139A
8 - Servicing data 1425 - 001 - 03.06.2020

HS 166A
M6 x 70.5 (2)8~12 Nm
M6 x 20 (2)8~12 Nm
1425 - 001 - 03.06.2020 Servicing data - 9

M6 x 72 Stud Bolt
14 mm Special Nut
8~12 Nm Torque
55~65 Nm Torque
M6 x 78 (2) Stud Bolt
8~12 Nm Torque
M6 x 30 (1) Bolt
8~12 Nm Torque
M6 x 16.5 (4) Bolt
8~12 Nm Torque
HS 139A
10 - Servicing data 1425 - 001 - 03.06.2020

HS 166A
M6 x 72 Stud Bolt
14 mm Special Nut
8~12 Nm Torque
55~65 Nm Torque
M6 x 78 (2) Stud Bolt
8~12 Nm Torque
M6 x 22 (2) Bolt
8~12 Nm Torque
M6 x 16.5 (4) Bolt
8~12 Nm Torque
1425 - 001 - 03.06.2020 Servicing data - 11

M6 x 25 (10) Bolt
8~12 Nm Torque
M6 x 26 (2) Bolt
11-13 Nm Torque
12 - Servicing data 1425 - 001 - 03.06.2020

5 Function overview
5.1 Product overview
2
8
1
3
4
6
7
5
HS 139A
1. Engine shroud
2. Nut
3. Engine cover
4. Flywheel housing
5. Fuel tank cap
6. Fuel tank
7. Fuel tank screws
8. Crankcase
1425 - 001 - 03.06.2020 Function overview- 13

5.2 Product overview
2
1
3
4
8
7
56
HS 166A
1. Engine shroud
2. Nut
3. Engine cover
4. Flywheel housing
5. Fuel tank cap
6. Fuel tank
7. Fuel tank screws
8. Crankcase
14 - Function overview 1425 - 001 - 03.06.2020

5.3 Serial numbers on the product
The engine serial number is found on the rear side of
the engine.
1425 - 001 - 03.06.2020 Function overview- 15

6 Repair instructions
6.1 To clean and examine the product parts
• Clean and examine all parts fully. You find more
instructions in the chapter for each part if special
tools or procedures are necessary.
• Replace damaged or defective parts.
• Always use original spare parts.
6.2 Starter
13
12
11
10
8
7
5
3
1
6
4
9
2
HS 166A
HS 139A
1. Retainer screw
2. Starter pawl holder
3. Washer
4. Friction spring
5. Starter pawls
6. Return spring
7. Recoil spring
8. Recoil slot
9. Starter pulley
10. Handle
11. Starter rope
12. Engine cover
13. Nuts
16 - Repair instructions 1425 - 001 - 03.06.2020

6.2.1 To remove and install the starter pulley
1. Remove the engine cover.
2. Remove the starter rope handle from the starter
rope.
3. Remove the screw (A).
A
4. Carefully remove the starter pulley .
5. Examine and replace all damaged parts. Refer to To
disassemble the starter unit on page 17 .
6. Install in the opposite sequence.
6.2.2 To disassemble the starter unit
WARNING: Use protective glasses. The recoil
spring can eject from the starter pulley and
cause injury.
1. Remove the starter housing.
2. Put pressure on the starter pulley with your hand.
Pull out the starter rope approximately 30 cm and
put the starter rope into the notch in the starter
pulley.
3. Decrease the pressure of your hand. Let the starter
pulley rotate clockwise slowly to decrease the
tension in the recoil spring.
4. Remove the screw and the washer. Remove the
starter pawl holder, the friction spring, the starter
pawls and the return spring.
5. Carefully remove the starter pulley.
6. Examine the starter rope. Replace the starter rope if
it is worn or damaged. Refer to To replace a
damaged starter rope on page 19 .
1425 - 001 - 03.06.2020 Repair instructions- 17

6.2.3 To assemble the starter pulley
WARNING: Use protective glasses. The recoil
spring can eject from the starter pulley and
cause injury.
1. Replace the starter rope if it is necessary. Refer to
To replace a damaged starter rope on page 19 .
2. Install the recoil spring if it is necessary. Refer to
To
install the recoil spring in the starter pulley on page
18 .
3. Lubricate the recoil spring in the starter pulley with
cold resistant grease.
4. Wind the starter rope 3 turns counterclockwise
around the starter pulley.
3r
5. Carefully put the starter pulley into the engine cover.
Make sure that the free end of the recoil spring
connects into the dedicated slot in the starter
housing.
6. Put the starter pawls and the return springs in
position. Make sure that the end of the starter pawls
are put into the slot in the starter pulley.
7. Attach the retainer screw.
8. Pull out the starter rope approximately 30 cm and
hold the starter pulley with your hand.
9. Put the starter rope in the notch in the starter pulley.
10. Wind the starter rope 1 turn counterclockwise
around the starter pulley.
11. Decrease the pressure of your hand and let the
starter pulley rotate clockwise slowly.
12. Make sure that you can turn the starter pulley ½ turn
clockwise with the starter rope fully pulled out.
6.2.4 To install the recoil spring in the starter pulley
WARNING: Use protective glasses. The recoil
spring can eject and cause injury.
1. Put the outer flange of the recoil spring into the slot
in the starter pulley.
2. Push the recoil spring into the starter pulley and turn
the starter pulley to wind the recoil spring. Continue
until the recoil spring is fully installed in the starter
pulley.
18 - Repair instructions 1425 - 001 - 03.06.2020

6.2.5 To replace a damaged starter rope
1. Remove the engine cover.
2. Remove the starter rope handle from the starter
rope.
3. Pull out the starter rope approximately 30 cm and
put the starter rope into the notch in the starter
pulley. Put pressure on the starter pulley with your
hand.
4. Decrease the pressure of your hand. Let the starter
pulley rotate clockwise slowly to decrease the
tension in the recoil spring.
5. Remove the remaining starter rope.
6. Do a check that the recoil spring operates correctly.
7. Put the new starter rope through the hole in the
starter housing and in the rope pulley.
8. Attach the starter rope to the starter pulley. Install
the knot in the dedicated cut-out in the starter pulley.
3r
9. Tighten the connection fully. Make sure that the free
end of the starter rope is as short as possible.
10. Wind the starter rope 3 turns counterclockwise
around the starter pulley.
11. Attach the starter rope handle (A) to the starter rope
(B).
A
B
12. Pull out the starter rope to its end position and hold
the starter pulley with your thumb.
13. Remove the starter rope from the notch in the starter
pulley.
14. Decrease the pressure of your thumb and let the
starter pulley rotate clockwise slowly.
15. Make sure that you can turn the starter pulley ½ turn
clockwise with the starter rope fully pulled out.
1425 - 001 - 03.06.2020 Repair instructions- 19

6.3 Air filter
6.3.1 To remove and install the air filter
WARNING: Use protective gloves.
1. Push the clips on the air filter cover.
2. Carefully remove the air filter cover (A) from the
engine.
3. Remove the air filter (B).
A
B
4. Examine the air filter for damages. Replace a
damaged air filter.
5. Clean and examine the air filter. Refer to To clean
the paper filter on page 20 .
6. Install in the opposite sequence.
6.3.2 To clean the paper filter
1. Remove the air filter cover and remove the paper
filter.
2. Hit the filter against a flat surface to make the
particles fall off.
CAUTION: Do not use solvent or
compressed air to clean the paper filter.
3. Put the air filter back. Make sure that the air filter
fully seals against the air filter holder.
4. Put the air filter cover back.
6.3.3 To remove and install the air filter holder
WARNING: Use protective gloves.
1. Remove the air filter. Refer to To remove and install
the air filter on page 20 .
2. Remove the 2 nuts and remove the air filter holder.
3. Install in the opposite sequence.
20 - Repair instructions 1425 - 001 - 03.06.2020