Workshop manual

543RBX, 543RBK, 553RBX

English

1239 - 001 -
 Contents

1 Introduction
1.1 Document description............................................ 3
1.2 Target group...........................................................3
1.3 Revisions................................................................3
1.4 Safety..................................................................... 3
1.5 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........................................... 5

4 Servicing data
4.1 Servicing data (543RBX, 543RBK)........................ 6
4.2 Servicing data (553RBX)......................................10

5 Servicing tools

6 Function overview
6.1 Type plate/Product serial number........................ 16
6.2 Fuel...................................................................... 16

7 Repair instructions
7.1 Product overview for repair instructions
(543RBX, 543RBK).................................................... 17
7.2 Product overview for repair instructions
(553RBX)................................................................... 18
7.3 To clean and examine the product parts..............19
7.4 Starter.................................................................. 19
7.5 Muffler.................................................................. 22
7.6 Air filter................................................................. 23
7.7 Carburetor............................................................ 23
7.8 Clutch and clutch drum........................................ 38
7.9 Ignition system..................................................... 40
7.10 Cylinder and piston............................................ 46
7.11 Crankshaft and crankcase................................. 51
7.12 Fuel tank............................................................ 56
7.13 Harness frame....................................................58
7.14 Handle and throttle trigger..................................59
7.15 Gearbox............................................................. 61

8 Troubleshooting

9 Technical data

2 1239 - 001 -
 1 Introduction
1.1 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.

1.2 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.

1.3 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.

1.4 Safety
WARNING: All personnel that repair or do
servicing on the product must read and
understand the safety instructions in this
workshop manual.

1.5 Servicing tools

The manual gives information about necessary servicing
tools. Always use original tools from Husqvarna.

1239 - 001 - Introduction - 3

 2 Safety
2.1 Safety definitions Use a protective helmet in locations where
Warnings, cautions and notes are used to point out objects can fall on you. Use approved
specially important parts of the manual. hearing protection. Use approved eye
protection.
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.
Use approved protective gloves.

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. Use heavy-duty slip-resistant boots.

Note: Used to give more information that is necessary in The product can cause objects to eject,
a given situation. which can cause injury.

Maximum speed of the output shaft.

2.2 General safety instructions
WARNING: Read the warning instructions that Keep a minimum of 15 m (50 ft) distance
follow before you use the product. 15 m
50FT
15 m
50FT
to persons and animals during operation
of the product.

The service center that repairs the product must have

safety devices that obey local regulations. Warnings and Risk of blade thrust if the cutting
cautions are used to point out specially important parts equipment touches an object that it does
of the workshop manual. not immediately cut. The product can cut
off body parts. Keep a minimum of 15 m
(50 ft) distance to persons and animals
2.3 Special safety instructions during operation of the product.
• When you use compressed air, do not point the
airflow in the direction of your body. Air can go into
the blood circulation and kill you.
Air purge bulb.
• Use eye protection when you do work on springs
that have tension.
• Do not use accessories that are not approved by the The direction to close the choke.
manufacturer. Do not do changes that are not
approved by the manufacturer. This can cause injury
or death to the operator or other persons. The direction to open the choke.
• Always use original spare parts and accessories.
• Use approved hearing protection. Noise from the
Keep all parts of your body away from the
product can result in permanent hearing loss.
hot surfaces.

2.4 Symbols on the product Noise emission to the environment refer to

WARNING! This product is dangerous. the European Community's Directive. The
Injury or death can occur to the operator emission of the product is specified in the
or bystanders if the product is not used Technical data chapter and on the label.
carefully and correctly. To prevent injury
to the operator or bystanders, read and
Note: Other symbols/decals on the product refer to
obey all safety instructions in the
certification requirements for other commercial areas.
operator's manual.

Please read the operator's manual

carefully and make sure that you
understand the instructions before use.

4 - Safety 1239 - 001 -

 3 Prepare and do servicing on the product
3.1 Maintenance schedule X = The instructions are given in this workshop manual.
* = General maintenance. The instructions are not given O = Refer to the operator's manual for instructions.
in this manual.

Maintenance Each 6
Daily Weekly Monthly
months
Clean the external surface. *
Examine the harness frame for damages. *
Do a check of the throttle trigger lockout and the throttle trigger. O
Make sure that the cutting attachment does not rotate at idle speed. *
Do a check of the stop switch. O
Examine the cutting attachment guard for damages and cracks. O
Examine the grass blade. Make sure that it is sharp, aligned with the cen-
*
ter and does not have damages on the blade or the center hole.
Examine the trimmer head for damages and cracks. Replace if it is dam-
O
aged.
Examine the handle and handlebar for damage and make sure that they
*
are attached correctly.
For cutting attachments with a support cup, tighten the nut fully. *
For cutting attachments with a locknut, tighten the locknut fully. *
Examine the transport guard for damage and make sure that it can be at-
*
tached correctly.
Examine the engine, the fuel tank and the fuel lines for leaks. *
Clean the air filter. Replace if it is necessary. X
Tighten nuts and screws. *
Examine the fuel filter for contamination and the fuel hose for cracks and
*
other defects. Replace if it is necessary.
Examine all cables and connections. *
Examine the starter and the starter rope for damages. *
Examine the vibration damping units for damages and cracks. *
Examine the spark plug. X
Clean the cooling system. O
Make sure that the bevel gear is filled to ¾ with grease. *
Clean the external surface of the carburetor and the area around it. *
Examine the clutch, clutch springs and the clutch drum for wear. Replace
X
if it is necessary.
Replace the spark plug. *
Lubricate the drive shaft. *

1239 - 001 - Prepare and do servicing on the product - 5

 4 Servicing data
4.1 Servicing data (543RBX, 543RBK)

2.5 - 4 Nm T27 3 - 6 Nm 3 - 6 Nm
T27 T27

9 - 13 Nm
M10

3 - 6 Nm T27
5 - 7 Nm T27
6 - 9 Nm T27

2.9 - 3.9 Nm
▲ 2.5 - 4 Nm T27
▲

7 - 11 Nm T27

5 - 8 Nm T27
10 - 15 Nm
12 mm

3 - 6 Nm T27
3 - 6 Nm T27 3 - 6 Nm
T27

11 - 17 Nm
5 - 7 Nm T27

4 - 6 Nm
T27

15 - 20Nm 17 mm

6 - Servicing data 1239 - 001 -

 2 - 3 Nm T27

3 - 5 Nm T27

3 - 5 Nm T27
2 - 4 Nm T27

15 - 20Nm 17 mm

3 - 5 Nm T27

1239 - 001 - Servicing data - 7

 3 - 5 Nm T27

1.5 - 2 Nm T27

8 - 10 Nm
M10
6 - 8 Nm
M5

5 - 10 Nm 13 mm 5 - 10 Nm 13 mm
6 - 8 Nm M5

6 - 8 Nm T27

RBX RBK

8 - Servicing data 1239 - 001 -

 1.6 - 2.5 Nm T27

1.6 - 2.5 Nm T27

2.5 - 3.5 Nm T27 2 - 3 Nm T27

2 - 3 Nm T27

1239 - 001 - Servicing data - 9

4.2 Servicing data (553RBX)

2.5 - 4 Nm T27 3 - 6 Nm
T27
3 - 6 Nm
T27

2.5 - 3.5 Nm T27

3 - 6 Nm
T27
3 - 6 Nm T27

6 - 9 Nm T27
0.4 - 0.8 Nm
7.8 - 8.3 Nm

▲ ▲

7 - 11 Nm T27
5 - 8 Nm T27

2.5 - 4 Nm T27
20 - 30 Nm
14 mm
3 - 6 Nm T27
3 - 6 Nm T27

11 - 17 Nm
5 - 8 Nm T27

4 - 6 Nm T27

10 - Servicing data 1239 - 001 -

 2 - 3 Nm T27

3 - 5 Nm T27

3 - 5 Nm T27

15 - 20Nm 17 mm

3 - 5 Nm T27

1239 - 001 - Servicing data - 11

 3 - 5 Nm T27

1.5 - 2 Nm T27

5 - 10 Nm 13 mm

6 - 8 Nm T27

12 - Servicing data 1239 - 001 -

 1.6 - 2.5 Nm T27

1.6 - 2.5 Nm T27

2.5 - 3.5 Nm T27 2 - 3 Nm T27

2 - 3 Nm T27

1239 - 001 - Servicing data - 13

 5 Servicing tools

1 2 3 4

5 6 7 8

9 10 11 12

13 14 15 16

14 - Servicing tools 1239 - 001 -

 17 18 19

Item Description Use to Article number

1 Piston stop Lock the piston. 522 43 18-01
2 Hex key Remove screws. N/A
3 Torx T27 Remove and attach torx screws. 502 71 27-03
4 Piston assembly kit Assemble the piston. 502 50 70-01
5 Removal tool for 543RBX, 543RBK Remove the starter pawl assembly. 581 96 55-01
6 Snap ring pliers Remove snap rings. N/A
7 Pliers N/A. N/A
8 Grease Lubricate the parts in the angle gear. 503 97 64-01
9 Ignition tester Spark strength check. 501 97 64-01
10 Pressure tester Pressure test. 531 03 06-23
11 Ignition cable pliers Repair the ignition cable. 502 50 06-01
12 Pin Lock the angle gear. 502 02 61-02
13 Assembly fixture Hold the product in position during 502 51 03-03
maintenance.
14 Bearing removal tool Remove the bearing from the crank- 505 38 17-09
case.
15 Pressure test plug Pressure test. 503 84 40-03
16 Rubber sheet (sealing plate) Pressure test. 502 54 11-02
17 Oil for the air filter Clean the air filter. 531 00 60-76
18 Cleaning agent Clean the product. 505 69 85-70
19 Removal tool for 553RBX Remove the driver. 521 53 33-01

1239 - 001 - Servicing tools - 15

 6 Function overview
6.1 Type plate/Product serial number Gasoline, litre Two-stroke oil, litre
The product serial number is given on the type plate. 2% (50:1)
Supply the model name and the article number when
you send an order for spare parts. 5 0.10
10 0.20
6.2 Fuel 15 0.30

6.2.1 To use fuel 20 0.40

CAUTION: This product has a two-stroke

6.2.4 To make the fuel mixture
engine. Use a mixture of gasoline and two-
stroke engine oil. Make sure to use the correct Note: Always use a clean fuel container when you mix
quantity of oil in the mixture. Incorrect ratio of the fuel.
gasoline and oil can cause damage to the
engine.
Note: Do not make more than 30 days quantity of fuel
mixture.
6.2.2 Husqvarna alkylate fuel
CAUTION: Do not use gasoline with an octane 1. Add half of the gasoline quantity.
number less than 90 RON (87 AKI). This can
cause damage to the product. 2. Add the full quantity of oil.
3. Shake the fuel mixture to mix the contents.
CAUTION: Do not use gasoline with more than 4. Add the remaining gasoline quantity.
10% ethanol concentration (E10). This can
cause damage to the product. 5. Shake the fuel mixture to mix the contents.
6. Fill the fuel tank.
CAUTION: Do not use leaded gasoline. This 6.2.5 To add fuel
can cause damage to the product.
• Always use a fuel container with an antispill valve.
• If there is some fuel on the container, remove the
We recommend Husqvarna alkylate fuel for best unwanted fuel and let the container dry.
performance. This fuel gives less dangerous exhaust • Make sure that the area near the fuel tank cap is
fumes compared to regular fuel. It keeps the engine clean.
clean and increases the engine life. Husqvarna alkylate
• Shake the fuel container before you add the fuel
fuel is not available in all commercial areas.
mixture to the fuel tank.
• Always use new unleaded gasoline with a minimum
octane number of 90 RON (87 AKI) and with less 6.2.6 To add fuel to the fuel tank
than 10% ethanol concentration (E10). 1. Stop the product.
• Use gasoline with a higher octane number if you
frequently use the product at continuously high 2. Put the product on a flat surface.
engine speed. 3. Loosen the fuel tank cap to release the pressure in
• Always use a good quality unleaded gasoline/oil the fuel tank.
mixture.
4. Remove the fuel tank cap.
6.2.3 Two-stroke oil 5. Fill the fuel tank to 80%.
• For best results and performance use Husqvarna
two-stroke oil, which is specially formulated for our 6. Tighten the fuel tank cap fully.
two-stroke engines. 7. Make sure that there is no leak in the fuel tank.
• If Husqvarna two-stroke oil is not available, you may
use another two-stroke oil of good quality that is
intended for air cooled engines.Contact your dealer
when you select an oil.
• Do not use two-stroke oil intended for water-cooled
outboard engines, also referred to as outboard oil.
• Do not use oil intended for four-stroke engines.

16 - Function overview 1239 - 001 -

 7 Repair instructions
7.1 Product overview for repair instructions (543RBX, 543RBK)

11

1 2

10
13
9 5

12

14

1. Starter 7. Flywheel
2. Muffler 8. Cylinder and piston
3. Air filter 9. Crankcase and crankshaft
4. Carburetor 10. Fuel tank
5. Clutch and clutch drum 11. Frame and harness
6. Ignition system 12. Handle and throttle trigger

1239 - 001 - Repair instructions- 17

13. Gearbox (543RBX) 14. Gearbox (543RBK)
7.2 Product overview for repair instructions (553RBX)

11

1 2

10

9 5

12 13

1. Starter 9. Crankcase and crankshaft

2. Muffler 10. Fuel tank
3. Air filter 11. Frame and harness
4. Carburetor 12. Handle and throttle trigger
5. Clutch and clutch drum 13. Gearbox
6. Ignition system
7. Flywheel
8. Cylinder and piston

18 - Repair instructions 1239 - 001 -

7.3 To clean and examine the product parts 3. Let the starter pulley rotate rearward until the spring
tension loosens.
• 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.

7.4 Starter

7.4.1 To disassemble the starter

WARNING: Use protective glasses to prevent
injury to the eyes if the recoil spring ejects.

1. Remove the 4 screws and the cylinder cover.

4. Remove the screw (A).

C
2. Remove the 4 screws and the starter unit.

5. Remove the starter pulley driver (B) and the spring

(C).

1239 - 001 - Repair instructions- 19

6. Remove the starter pulley. The recoil spring is in the 4. Attach a new starter rope to the starter pulley. Make
starter housing. a small knot and make sure that it can be put into
the notch in the pulley.
WARNING: Be very careful when you
remove the starter pulley. The recoil spring
can eject and cause injury to you.

7. Remove the recoil spring from the starter housing.

7.4.2 To assemble the starter

1. Put the recoil spring in the starter housing and hold it
down with your thumb.
WARNING: Use eye protective glasses. The
recoil spring can eject and cause injury. The
recoil spring is supplied with a steel wire
and a plastic package. Open the plastic
package carefully to prevent injury.

2. Make sure that the catch of the spring is aligned with

the groove (A).

A
5. Attach the recoil spring and the starter pulley driver
to the starter pulley.
6. Attach the screw to the pulley and tighten the screw
to the correct torque.
7. Pull the starter rope through the handle. Do a double
knot on the starter rope and pull it into the handle.

3. Use a screwdriver to push the spring into the groove

in the starter housing and remove the steel wire.

20 - Repair instructions 1239 - 001 -

8. Tighten the recoil spring. 3. Use the removal tool to remove the starter pawl
assembly. Refer to Servicing tools on page 14.

9. Attach the starter unit to the crankcase.

4. Examine the starter pawl assembly.

a) Clean the starter pawl assembly if it is dirty.
b) Remove the snap ring that holds the starter
pawl. Remove the starter pawls and springs.

CAUTION: Make sure the starter units

attached correctly into the muffler guard.

7.4.3 To replace the starter pawl assembly

1. Remove the starter unit. c) Replace the parts in the starter pawl assembly if
they are damaged.
2. Remove the spark plug cap and the spark plug. Put
a piston stop in the spark plug hole to lock the axle. 5. Assemble the starter pawl assembly in the opposite
sequence to how it was disassembled.
6. Attach the starter pawl assembly to the crankshaft.
7. Remove the piston stop and install the spark plug
and spark plug cap.
8. Attach the cylinder cover.
9. Attach the starter unit.

1239 - 001 - Repair instructions- 21

7.5 Muffler 5. Remove the screws and the holder, if it is
necessary.
7.5.1 To remove and install the muffler
1. Remove the 4 screws and the cylinder cover.

6. Install the muffler in the opposite sequence.

7.5.2 To clean and examine the muffler

WARNING: Risk of burn injury or fire. The
muffler becomes very hot during operation.

2. Remove the 3 screws (A and B), the muffler (C) and WARNING: Risk of fire. The exhaust gases are
the heat shield (D). hot and can contain sparks.

1. Clean the muffler with a wire brush.

2. Examine the muffler for wear and damage. Replace
the muffler if it is damaged.

D
C

E
F
B

3. If it is necessary to remove the muffler guard (E),

remove the starter unit first. Refer to Starter on page
19.
4. Remove the screw (F) and the muffler guard (E).

22 - Repair instructions 1239 - 001 -

7.6 Air filter damaged air filter. Clean the air filter at an
interval of 25 hours of operation.
7.6.1 To remove and install the air filter
1. Turn the engine around its axle to get access to the If you use an air filter for a long time, it cannot be fully
air filter. cleaned. Replace the air filter with a new one at regular
intervals.
1. Clean the air filter with compressed air.
2. Clean the inner surface of the filter cover. Use
compressed air or a brush.
3. Make sure that the filter is dry before you assemble
the air filter again.

7.7 Carburetor

7.7.1 Carburetor design

7.7.1.1 Carburetor parts

The carburetor can be divided into 3 different function
units: the metering unit, the blending unit, and the pump
unit.
Metering unit
The needle valves (A) and the fuel control functions are
found here. The inlet valve (B) and control diaphragm
(C) are important to the function of the carburetor.

2. Remove the air filter cover and the air filter.

A A

B C

Blending unit
In this section of the carburetor the fuel and the air are
mixed to the correct proportions. The choke valve (B)

3. Install the air filter in the opposite sequence.

7.6.2 To clean the air filter

CAUTION: Always replace a damaged air filter.
The wear on the engine increases with a

1239 - 001 - Repair instructions- 23

and throttle valve (A) are found here. The main jet is in diaphragm is operated by pressure variations in the
the middle of the venturi. engines crankcase through an impulse channel (B). If
the impulse channel is blocked, by grease or an
incorrectly installed gasket, the pump unit does not
operate.

A
B

A B

Pump unit
This is where the pump diaphragm (A) that supplies fuel
to the metering unit from the fuel tank is found. The

24 - Repair instructions 1239 - 001 -

7.7.2 Carburetor (543RBX, 543RBK)

7.7.2.1 Overview of the carburetor (543RBX, 543RBK)

1239 - 001 - Repair instructions- 25

E Gasket 7.7.2.2 To disassemble the carburetor
1. Turn the engine around its axle to get access to the
F Diaphragm
air filter and carburetor.
G Cover
H Gasket
I Diaphragm
J Fuel screen
K Main jet
L Plug

2. Remove the air filter cover and the air filter.

26 - Repair instructions 1239 - 001 -

3. Remove the fuel hoses (A and B) from the primer 8. Remove the 3 screws and the distance piece, the
pump. gaskets and the throttle wire, if it is necessary.

C D

9. Remove the 4 screws and the cover. Remove the

metering diaphragm (F) and the gasket (E). Examine
B the diaphragm for damage and wear on the pin.

4. Remove the fuel hose (C) from the carburetor.

5. Remove the throttle wire (D) from the carburetor.
6. Remove the 2 screws and the air filter holder, the
gaskets and the carburetor.
E

7. Remove the primer pump from the air filter holder, if

it is necessary.

1239 - 001 - Repair instructions- 27

10. Connect the pressure tester to the fuel hose. Lower b) Examine the lever arm and the needle valve for
the carburetor in a vessel with gasoline to find leaks. wear and damage.
Do a test of the pressure at 50 kPa.

c) Remove the screw and remove the cover (G).

11. If there is a leakage, remove the needle valve.

a) Loosen the bolt and remove the lever arm, axle,
needle valve and spring. G

d) Remove the gasket (H) and the diaphragm (I).

Examine the diaphragm for damage.
e) Remove the fuel screen (J).

28 - Repair instructions 1239 - 001 -

 f) Remove the jet needles. 7.7.2.3 To assemble the carburetor
1. Blow compressed air through the channels of the
carburetor.
2. Install a new main jet (K).

3. Attach the valves and springs.

g) Remove the main jet (K).
4. Replace the fuel screen if it is damaged or cannot be
K cleaned.
5. Assemble the components of the carburetor in the
opposite sequence to how they were disassembled.
Refer to To disassemble the carburetor on page 26.
6. Make sure that the lever arm is 0.66 mm +- 0.16 mm
below the plane of the carburetor surface. If it is
necessary, the lever arm can be bent.

h) Remove the valves and springs. Always replace

the valves and springs.

1239 - 001 - Repair instructions- 29

7. Attach the pressure tester to the fuel inlet on the 9. Make sure that the air hole is open and attach the
carburetor. Pump up the pressure to 50 kPa. Lower cover.
the carburetor in a container with gasoline to find
leaks.

10. Install the carburetor in the opposite sequence to

how it was removed.
CAUTION: Examine the carburetor. Replace
the carburetor if it is necessary.

8. Assemble the gasket (E) and diaphragm (F) on the

carburetor. Attach the cover and tighten the 4
screws.

30 - Repair instructions 1239 - 001 -

7.7.3 Carburetor (553RBX)

7.7.3.1 Overview of the carburetor (553RBX)

X
Y

AA

AB

AC

AD

AL
AE

W
AF U
AJ T
S
AI
AG Q

R
P
AH

AK

1239 - 001 - Repair instructions- 31

P Diaphragm AA Connecting 3. Remove the fuel hose (A).
rod
Q Gasket AB Cover
R Diaphragm AC Gasket
S Screw AD Diaphragm
T Axle AE Fuel screen
A
U Lever arm AF Low speed
needle
V Cover AG High speed
needle
W Needle AH Hub cap
valve
X Screw AI Plug
Y Body AJ Main jet
Z Sealing AK Grease nip-
rings ple
AL Impulse
channel 4. Remove the fuel hoses (B) and (C) from the air
purge bulb (D). Remove the air purge bulb (D) from
7.7.3.2 To disassemble the carburetor the filter housing.
1. Turn the engine around its axle to get access to the
air filter and the carburetor. C

2. Remove the 2 screws and the air filter. B

5. Remove the screw (E) from the holder of the the air
purge bulb.

32 - Repair instructions 1239 - 001 -

6. Remove the 2 screws (F) and the plate (G). 11. Remove the 4 screws and the cover. Remove the
control diaphragm (P), gasket (Q) and cover (V).
K Examine the diaphragm for damage and wear on the
pin (R).
J

Q
L
R
P

F H M
V
7. Remove the air filter holder (H), bracket holder (I)
and carburetor (J).
8. Remove the gasket (K).
9. Remove the small screw (L) and the throttle wire (M)
12. Connect the pressure tester to the fuel hose. Lower
from the bracket holder (I).
the carburetor in a container with gasoline to find
10. Remove the screws (N) and (O) and the air filter leaks. Do a test of the pressure at 50 kPa.
holder (H) from the bracket holder (I) and the
carburetor (J).

J I

N
O

13. If there is a leakage, remove the needle valve.

1239 - 001 - Repair instructions- 33

14. Loosen the bolt and remove the lever arm, axle, 17. Remove the bolt and the cover (AB).
needle valve and spring.

AB

AC

AD
15. Examine the wear to the lever arm and the needle
valve for damage.

AE

18. Remove the gasket (AC) and the diaphragm (AD).

Examine the diaphragm for damage.
Note: Examine the diaphragm for damage to the
16. Remove the screw (X) and remove the air intake valve tongues. If the valve tongues are bent, the
housing (Y). Make a note of the position of the pump will not operate correctly.
connecting rod (AA). Do not remove the sealing
rings (Z).
19. Remove the fuel screen (AE).
X Y Note: Carefully remove the fuel screen. Clean the
Z AA fuel screen or replace if it is damaged.

20. Remove the needle caps (AH) and remove the high
speed needle (AG) and the low speed needle (AF).

AF

AG AH

Note: The plugs cannot be disassembled if there is

no pin on the plug in the middle of the slot in the
carburetor housing. Refer to the arrow in the
illustration.

34 - Repair instructions 1239 - 001 -

21. Remove the main jet (AJ) and remove the plug (AI). 7. Attach and adjust the jet needles.

AF
AJ

AI

AG AH

7.7.3.3 To assemble the carburetor

1. Blow compressed air through the channels of the Note: The end of the high speed needle (AG) is
carburetor. slightly thinner than that of the low speed needle
(AF).
2. Examine the throttle and throttle shaft and replace if
it is necessary.
8. Attach the needle caps (AH).
3. Attach a new plug (AI).
9. Attach the pressure tester to the fuel inlet on the
carburetor.

AI 10. Pump up the pressure to 50 kPa. Lower the

carburetor in a container with gasoline to find leaks.

AJ

4. Install in a new main jet (AJ).

5. Attach the different parts of the metering unit in the
opposite sequence to how it was disassembled.
Refer to To disassemble the carburetor on page 32.
6. Use a transparent material to make sure that the
lever arm is level with the lower surface of the
carburetor housing.

CAUTION: Make sure that there are no

leaks. If a leak occurs, examine the
carburetor or replace the carburetor.

1239 - 001 - Repair instructions- 35

11. Attach the gasket (Q). 15. Attach the pump diaphragm (AD), the gasket (AC)
and the cover (AB).
AE
X
Z

AA
Y

Q
AB

P
AC

AK
V
AD

12. Attach the control diaphragm (P). Make sure that the
handle points in the direction of the lever arm.
13. Attach the cover (V). Make sure that the hose
connector (AK) is aligned to the choke valve.
14. Attach the fuel screen (AE).

16. Attach the connecting rod (AA) into the lever arms of
the throttle shafts.
17. Attach the air intake housing (Y) and the sealing
rings (Z).
18. Attach the screw (X).
19. Install the carburetor in the opposite sequence to
how it was removed.

7.7.4 Adjustments of the carburetor

WARNING: Do a test with all the parts
assembled correctly. If a part is missing, there is
a risk that the clutch becomes loose and causes
serious injury.

During a test of the engine, make sure that the clutch,

the clutch cover, the shaft and the bevel gear are
assembled correctly.

7.7.4.1 To adjust the idle speed

The idle speed is adjusted at the factory before the
product is supplied. An adjustment of the idle speed can
become necessary because of changes in the operation
conditions.

36 - Repair instructions 1239 - 001 -

 WARNING: If the cutting attachment does not speed and makes it possible to increase engine speed
stop when you adjust the idle speed, speak to quickly.
your servicing dealer. Do not use the product The correct adjustment of the carburetor can change if
until it is correctly adjusted or repaired. the air moisture, temperature and air pressure changes.
The carburetor has 3 adjustment controls.
• The idle speed is correct when the engine operates
smoothly in all positions. The correct idle speed is • L = low speed jet
set when the product does not stop and the cutting • H = high speed jet
equipment does not rotate. • T = idle adjustment
1. Start the engine and operate the product at half
speed for approximately 2 minutes until the engine 553RBX 543RBX, 543RBK
becomes warm.
2. Turn the idle adjustment screw clockwise until the
cutting attachment starts to rotate.

T T
L H H L

Turn the jets clockwise to get less fuel in the mixture and
counterclockwise to get more fuel in the mixture. Less
fuel in the mixture gives a higher engine speed and
more fuel in the mixture gives lower speed.
The idle adjustment screw adjusts the position of the
throttle when the engine is at idle speed. Turn the idle
adjustment screw clockwise to get a higher idle speed
and turn it counterclockwise to get a lower idle speed.
Note: The illustration refers to 543RBX, 543RBK, but
Carburetor adjustments at the factory
the procedure applies also to 553RBX.
During tests at the factory, the carburetor is adjusted to
give more fuel to the mixture of fuel and air. This
3. Turn the idle adjustment screw counterclockwise adjustment must be kept during run-in of the engine.
until the cutting attachment stops. After run-in of the engine, it is necessary to do a fine
adjustment of the carburetor.
Note: Refer to Technical data on page 70 for the
recommended idle speed. 543RBX, 553RBX
543RBK
Carburetor function H 1¾±½ 2⅞±½
The carburetor supplies a mixture of fuel and air to the
L 3¼±½ 2⅛±½
engine. The quantity of this mixture is controlled by the
throttle. The proportions of fuel and air in the mixture is
controlled by the adjustable high and low speed jets. These conditions are necessary to get the correct result:

The jets must be correctly adjusted for the engine to • The spark plug is not defect and has a correct
have maximum power at different speeds. A correctly electrode gap.
adjusted carburetor gives the engine maximum power at • The air filter is not defect and is clean and correctly
different speeds. It also gives the engine a smooth idle installed.
• There are no leaks between the cylinder and the
distance piece and the carburetor and the insulator.
The screws are tight.
• The fuel filter is clean.

1239 - 001 - Repair instructions- 37

• The exhaust port is not blocked. 7.8 Clutch and clutch drum
• The cutting attachment is correctly installed. The
trimmer line is of standard length. 7.8.1 To disassemble the clutch and the clutch
• The fuel quality is correct, minimum 89 octane. drum
Fine adjustment (543RBX, 543RBK, 553RBX) 1. Pull up the knob and remove the drive shaft tube.
After run-in of the engine, it is necessary to do a fine
adjustment of the carburetor. Before fine adjustment of
the carburetor, operate the engine for 4 minutes to make
it warm.
To adjust the low speed needle (543RBX, 543RBK)
Use Husqvarna T45 trimmer head with trimmer line ø
3.0 mm. The length of the trimmer line will be adjusted
by the knife on the original cutting attachment guard.
1. Turn the low speed needle (L) clockwise for the
position that gives the maximum engine speed.
2. Turn the low speed needle (L) counterclockwise until
the engine speed decreases to 800 rpm.
To adjust the high speed needle (543RBX, 543RBK)
1. Adjust the idle speed to 3000 rpm with the idle
speed screw.
2. Turn the low speed needle clockwise to maximum 2. Remove the throttle wire (A) from the throttle wire
idle speed. joint (B) and the cables (C).
3. Adjust the idle speed to 3800 rpm with the idle
speed screw.
4. Turn the low speed needle counterclockwise to
adjust the engine speed to 3000 rpm. C
5. Apply full throttle. The speed must be a minimum of A
9000 rpm. If the speed is lower than this, adjust with B
a high speed needle.
To adjust the carburetor (553RBX)
Use Husqvarna T45 trimmer head with silent cord ø 3.0
mm. The length of the trimmer line will adjust by the
knife on the original cutting attachment guard.
1. Adjust the idle speed to 2800 rpm with the idle
speed screw.
2. Turn the low speed needle clockwise to maximum
idle speed.
3. Adjust the idle speed to 3600 rpm with the idle
speed screw. 3. Remove the spark plug cap from the spark plug.
Remove the spark plug and put a piston stop in the
4. Turn the low speed needle counterclockwise to spark plug hole to prevent movement of the piston.
adjust the engine speed to 2800 rpm.
5. Apply full throttle. The speed must be a minimum of
11000 rpm. If the speed is lower than this, adjust the
high speed needle.
6. Make sure that the needle caps are in position and
that the jet needles cannot turn counterclockwise.

38 - Repair instructions 1239 - 001 -

4. Remove the 4 screws and the clutch drum housing. 7. Use pliers to remove the snap ring (F) and the
bearing (G).

7.8.2 To clean and examine the centrifugal clutch

1. Examine the spring and outer edge for wear and
damage. The thickness of the outer edge must be a
minimum of 1.0 mm at the most worn point.

5. Remove the screws, the washers and the clutch.

2. Examine the clutch drum for wear. Replace the
clutch drum if it is worn or damaged.
3. Measure the diameter of the clutch drum. Replace
the clutch drum if the diameter is more than 78.5
mm.

6. Use pliers to remove the small snap ring (D) and the
clutch drum (E).

G 4. Examine the centrifugal clutch for damage.

5. Replace damaged parts.
6. Clean all parts.

D
E
F

Note: If it is not easy to remove the clutch drum, use

a hot air gun to increase the temperature of the
clutch drum cover.

1239 - 001 - Repair instructions- 39

7.8.3 To install the centrifugal clutch 7.9.3 To do a spark test of the ignition module
1. Put some grease on the clutch screw, but not on the 1. Disconnect the spark plug cable from the spark plug.
thread.
2. Disconnect the spark plug from the cylinder.
3. Connect the ignition tester to the spark plug cap and
ground the clip to the cylinder.

2. Install the centrifugal clutch in the opposite

sequence to how it was removed.

7.9 Ignition system

7.9.1 Introduction
The engine has an electronic ignition system fully
without moving parts. A defective component cannot be
repaired, but must be replaced by a new component.
If the engine does not fire, the ignition module can be
damaged. Before you replace the ignition module, do 4. Use the knob to adjust the distance between the 2
the tests that follow. electrodes. Set the distance to 6 mm.

7.9.2 To examine the spark plug Note: 6 mm is 6 marks on the scale.

CAUTION: Always use the recommended spark

plug type. Incorrect spark plug type can cause 5. Pull the starter rope handle with force. If the ignition
damage to the product. module operates correctly, there is a clear blue
spark between the electrodes. If there is no spark,
examine the spark plug cable.
• Examine the spark plug if the engine is low on
power, is not easy to start or does not operate
correctly at idle speed.
• To decrease the risk of unwanted material on the
spark plug electrodes, obey these instructions:
a) Make sure that the idle speed is correctly
adjusted.
b) Make sure that the fuel mixture is correct.
c) Make sure that the air filter is clean.
• If the spark plug is dirty, clean it and make sure that
the electrode gap is correct, refer to Servicing data
on page 6.

• Replace the spark plug if it is necessary.

40 - Repair instructions 1239 - 001 -

7.9.4 To examine the spark plug cable 5. Put the spring into the new hole.
If there is no spark when you do a spark test of the
ignition module, you must examine the spark plug cable.
1. Remove the ignition module. Refer to To
disassemble the ignition system on page 42.
2. Remove the spark plug cable from the spark plug
cap.

6. Put the spark plug cable with the open spring into
the other slot in the assembly pliers. Close the
assembly pliers to bend the spring.

3. Remove the spring from the spark plug cable. Turn

the spring to remove it from the spark plug cable.

CAUTION: Make sure that the spring is bent

90 degrees along the spark plug cable.

7. Push the spark plug cable into the spark plug cap.

4. Put the end of the spark plug cable in the assembly

pliers. Close the assembly pliers to make a new
hole.

1239 - 001 - Repair instructions- 41

8. Use the assembly pliers or a screwdriver to align the 7.9.5 To disassemble the ignition system
spring with the hole in the spark plug cap. 1. Pull up the knob and remove the drive shaft tube.

2. Remove the throttle wire (A) from the throttle wire

WARNING: Be very careful to prevent
joint (B). Remove the cables (C).
damage to the spark plug cap. A damaged
spark plug cap can cause an electrical
shock.

C
A
B

42 - Repair instructions 1239 - 001 -

3. Remove the 4 screws and the cylinder cover. 5. Remove the screws, the flywheel cover and clutch
drum assembly.

4. Remove the spark plug cap from the spark plug.

Remove the spark plug and put a piston stop in the 6. Remove the clutch.
spark plug hole to prevent movement of the piston.

1239 - 001 - Repair instructions- 43

7. Remove the screw, the cable (D) and the cable (E) 10. Remove the nut and remove the flywheel. Remove
from the ignition module. the key from the crankshaft.

8. If it is necessary, pull up the cables (D and E) from

7.9.6 To examine the ignition system
behind the crankcase.
1. Examine the clutch and the flywheel for wear or
damages. Replace the parts if it is necessary.
2. Examine the ignition module and its cables. Replace
the ignition module if it is damaged.
D

H F
G

9. Remove the screw and remove the ignition module.

44 - Repair instructions 1239 - 001 -

7.9.7 To assemble the ignition system 3. Connect the cables (C) and (D) to the ignition
1. Attach the flywheel. Make sure that the key is in the module.
correct position when you install the flywheel.
C

4. Use a feeler gauge to make sure that the distance

2. Attach the sleeves (A) and ignition module (B) to the between the ignition module and the flywheel is 0.3
cylinder. mm. Tighten the screws.

A
B

5. Put some grease on the clutch screw, but not on the

thread.

6. Attach the remaining parts in the opposite sequence

to how they were removed.

1239 - 001 - Repair instructions- 45

7.10 Cylinder and piston 13. Put a cloth above the crankcase to make sure that
no dirt goes into the crankcase.
7.10.1 To disassemble the cylinder and piston
1. Pull up the knob and remove the drive shaft tube.
2. Remove the cylinder cover.
3. Remove the spark plug.
4. Remove the flywheel cover and clutch drum
housing.
5. Remove the clutch.
6. Remove the ignition module.
7. Remove the starter.
8. Remove the muffler and heat shield.
9. Remove the air filter cover, the air filter and the air
filter holder.
10. Remove the carburetor, the distance piece and the
gaskets.
11. Loosen the 4 screws (A). Move the cylinder (B)
rearward and forward and lift it.
14. Remove the piston pin snap rings.

Note: Make sure that the snap ring does not eject.
Keep your thumb on the snap ring.

CAUTION: Do not turn the cylinder when

you lift it. It can cause damage to the
cylinder.

12. Remove and discard the cylinder base gasket (C).

46 - Repair instructions 1239 - 001 -

15. Push the piston pin from the piston with a piston pin 7.10.2 To clean the cylinder and piston
rod.
CAUTION: Be careful when you clean the piston
and cylinder. The soft aluminum parts are easily
damaged.

• Remove the carbon deposits from these parts:

16. Remove the piston. Remove the needle bearing and a) The top of the piston.
the 2 washers. b) The combustion chamber of the cylinder.
c) The exhaust port of the cylinder.
• Use a screwdriver to remove dirt particles from the
cooling fins.

17. Remove the piston rings, if it is necessary.

• Clean all parts.
• Clean the piston ring groove.

7.10.3 To examine the cylinder

• Make sure that the surface layer of the cylinder is
not worn, especially in the top end of the cylinder.

1239 - 001 - Repair instructions- 47

• Make sure that the cylinder does not have score • Measure the piston ring play (B). Replace the piston
marks. ring if the piston ring play is larger than 0.1 mm.
• Put the piston ring in the cylinder and measure the
space with an air gap tool. The space must not be
more than 1 mm.

7.10.4 To examine the piston

• Make sure that the piston ring can move freely in the
groove.
• Examine the surface of the piston for damage and
wear.
• Examine the piston pin.
a) Make sure that the piston pin bearing is not
damaged. 7.10.5 To assemble the cylinder and piston
b) Make sure that the piston pin does not have 1. Carefully put the piston ring on the piston. Make
discolorations. sure that you do not cause damage to the piston ring
c) Make sure that the piston pin does not have or the piston.
damages on the surface against the bearing. 2. Lubricate the needle bearing with 2-stroke oil and
d) If the piston moves too easily, replace the piston put it into the connecting rod. Make sure that the
and the piston pin. needle bearing moves freely in the connecting rod.
e) Make sure that the needle bearing does not
have discolorations or damages.
• Examine the snap rings. If the snap rings have
cracks or discoloration, replace them.
• Measure the piston ring groove (A). Replace the
piston if the groove is larger than 1.3 mm.

3. Attach the piston to the connecting rod. Point the

arrow at the piston top in the direction of the exhaust
port.
Note: Put a cloth in the crankcase opening to make
sure that the piston rings do not fall into the
crankcase. Make sure that the piston rings are
correctly attached in the grooves.

48 - Repair instructions 1239 - 001 -

4. Push the piston pin into the piston and attach the 9. Assemble the remaining parts of the cylinder and
snap ring. piston in the opposite sequence to how they were
disassembled. Refer to To disassemble the cylinder
5. Put a new cylinder base gasket on the crankcase. and piston on page 46.

7.10.6 To do a leak test of the cylinder

1. Turn the engine around its axle to get access to the
air filter.

6. Attach the support plate from the piston assembly

kit. Refer to Servicing tools on page 14.
7. Use the clamp from the piston assembly kit to
compress the piston ring. Carefully push the piston
into the cylinder opening.

2. Remove the air filter cover and the air filter.

CAUTION: Do not turn the cylinder. The

piston rings break easily.

8. Tighten the 4 screws to the correct torque. Refer to

Servicing data on page 6.

1239 - 001 - Repair instructions- 49

3. Remove the cylinder cover. 5. Loosen, but do not remove, the 2 screws that hold
the carburetor and air filter holder. Put a rubber
sheet between the carburetor and the distance
piece. Tighten the 2 screws.

4. Loosen the 3 screws that hold the muffler. Put a

rubber sheet between the muffler and the cylinder.
Tighten the 3 screws.

6. Remove the spark plug and attach a pressure tester

plug. Attach the pressure tester.

7. Increase the pressure to 0.8 bar and wait for 30

seconds. Make sure that the pressure is not less
than 0.6 bar.
8. Remove the pressure tester and the pressure
vacuum tester.

50 - Repair instructions 1239 - 001 -

7.11 Crankshaft and crankcase 10. Remove the 4 screws (D) and the crankcase (E).

7.11.1 To disassemble the crankshaft and E

crankcase G
1. Pull up the knob and remove the drive shaft tube.

2. Remove the throttle wire (A) from the throttle wire

joint (B). Remove the cables (C).
11. Remove the screw (F) and the muffler guard (G)
from the crankcase.

C
A
B

3. Remove the ignition system and the clutch. Refer to

Ignition system on page 40.
4. Remove the spark plug. Refer to Ignition system on
page 40.
5. Remove the air filter cover. Refer to To remove and
install the air filter on page 23.
6. Remove the carburetor and the distance piece.
Refer to Carburetor on page 23.
7. Remove the starter and drive. Refer to Starter on
page 19.
8. Remove the muffler. Refer to Muffler on page 22.
9. Remove the cylinder and the piston. Refer to
Cylinder and piston on page 46.

1239 - 001 - Repair instructions- 51

12. Remove the screw (L) and remove the grass guard 16. Use a screwdriver or equivalent to remove the seal
(M). ring from the crankcase halves.

K CAUTION: Remove the seal rings carefully.

The crankcase is easily damaged.
M
17. Discard the seal ring.
N 18. Use a snap ring pliers to remove the snap ring from
the crankcase on the flywheel side.
L

13. Remove the 4 screws (H) from the crankcase half (I)
on the flywheel side.
14. Remove the gasket (K) and the guides (J).
15. Remove the crankshaft (N) from the crankcase half
(O) on the starter side.

52 - Repair instructions 1239 - 001 -

19. Increase the temperature of the crankcase halves to b) On the starter side: Carefully tap on the bearing
120ºC with a hot air gun. removal tool with a rubber hammer until the
bearing falls out.

20. Remove the bearings from the crankcase halves.

a) On the flywheel side: Carefully tap on the
bearing removal tool with a rubber hammer until
the bearing falls out.

1239 - 001 - Repair instructions- 53

7.11.2 To clean and examine the crankshaft and 7.11.3 To assemble the crankshaft and crankcase
crankcase 1. Use snap ring pliers to attach the snap ring to the
The crankshaft cannot be repaired, replace it if it is worn crankcase half on the flywheel side.
or damaged.
1. Examine the connecting rod. Replace the crankshaft
if the connecting rod is worn, damaged or has
discoloration.

2. Put the bearings in the crankcase halves. Carefully

tap on the bearing removal tool with a rubber
hammer until the bearings are in position. Make sure
that the bearings are against the snap ring on the
flywheel side.
2. Examine the crankshaft bearing. Make sure that
there is no radial play in the connecting rod. Make
sure that there is axial play to sufficiently lubricate
the crankshaft bearing.

3. Examine the crankcase halves for cracks and

damages.

54 - Repair instructions 1239 - 001 -

3. Attach the sealing rings. 5. Lubricate the crankshaft with some oil. Move the
crankcase half on the clutch side into position.

4. Put the crankshaft in the crankcase half on the

flywheel side. Lubricate the stub axle with some oil
and carefully move the crankshaft into the bearing.

6. Tighten the 4 screws crosswise. Make sure that the

crankshaft can rotate easily.

1239 - 001 - Repair instructions- 55

7. Attach the grass guard and muffler guard. 3. Remove the throttle wire (A) from the throttle wire
joint (B). Remove the cables (C).

C
A
B

8. Assemble the remaining parts in the opposite

sequence. 4. Turn the engine around its axle to access the air
filter and carburetor.
7.12 Fuel tank

7.12.1 To remove and install the fuel tank

1. Make sure that the fuel tank is empty.
2. Pull up the knob and remove the drive shaft tube.

56 - Repair instructions 1239 - 001 -

5. Remove the air filter cover and the air filter. 8. Remove the 4 screws and lift up the engine and fuel
tank.

6. Remove the fuel hoses (A and B) from the air purge

bulb.

9. Install the fuel tank in the opposite sequence.

C D

7. Remove the fuel hose (C) from the carburetor.

Note: Do not remove the throttle wire joint (D) unless
it is necessary.

1239 - 001 - Repair instructions- 57

7.12.2 To remove and install the fuel filter 7.13 Harness frame
Note: To remove the fuel filter it is not necessary to
remove the fuel tank. 7.13.1 To disassemble and assemble the harness
frame
1. Pull up the knob and remove the drive shaft tube.
1. Loosen the fuel tank cap.
2. Use a fuel filter hook to pull up the fuel filter.

2. Remove the throttle wire (A) from the throttle wire

joint (B) and remove the cables (C).

C
A
3. Push the fuel hose clamp to remove the fuel filter.
B
4. Install the fuel filter in the opposite sequence.

7.12.3 To clean and examine the fuel tank and fuel

filter
• Clean the fuel filter with a brush. If the fuel filter
cannot be fully cleaned, replace it.
• Make sure that there are no cracks or leaks in the
fuel hose.
• Make sure that the connection neck is installed as
far as possible into the fuel hose. Make sure that the
O-ring is tight against the tube and holds the fuel
filter in position.

7.12.4 Fuel tank cap

The fuel tank cap cannot be repaired. If the engine stops
after a short period of time or if the O-ring on the fuel
tank cap is damaged, the fuel tank cap must be
replaced.

58 - Repair instructions 1239 - 001 -

3. Remove the bolt (D), cable (E), washer (F) and the i) Remove the 2 stop screws (S) and its washers
engine. and nuts, if it is necessary.

7.14 Handle and throttle trigger

7.14.1 To disassemble the throttle handle

1. Loosen the screws.

E F

4. Disassemble the harness and support plate from the

frame.
2. Remove the 4 screws and the handle cover.

G
J

H
R

Q
L
P
O
K

T
M
N

a) Remove the bag (G) from the frame.

b) Remove the waist belt (H) from the waist belt
(M).
c) Remove the shoulder strap assembly (J and I) in
front of the frame. Remove the shoulder strap (J)
from the shoulder strap assembly (J and I).
d) Remove the 5 screws (K) and the 5 grommet (L)
from the frame and remove the waist belt (M).
e) Remove the 3 screws (N).
f) Remove the 3 spring holder (O) from the 3
vibration damping units (Q).
g) Remove the 3 screws (P) from the support plate
(R) and remove the vibration damping units (Q).
h) Remove the screw (T) to remove the ground
cable, the washers and the nut from the frame.

1239 - 001 - Repair instructions- 59

3. Push the front handle forward to remove the right 5. Remove the throttle trigger, link arm, springs and the
handle half from the shaft. Examine the 4 vibration throttle lockout.
damping units. Remove the vibration damping units
and replace them, if it is necessary.

4. Remove the throttle wire from the throttle trigger.

6. Remove the cables from the start switch.

60 - Repair instructions 1239 - 001 -

7.14.2 To assemble the throttle handle 7.15.1 To disassemble the bevel gear (543RBX,
1. Put the cables and throttle wire in the correct 543RBK)
positions. Make sure that the cables are attached to 1. Loosen the screw (A) and remove the splash guard.
the handle half.

2. Remove the screw (B) and lift off the plate (C).
3. Loosen the screws (D) and pull the gearbox from the
shaft.
4. Remove the sealing ring from the output shaft with a
screwdriver.

2. Assemble the remaining parts in the opposite

sequence.
CAUTION: To prevent damage to the
cables, make sure that they stay in their
correct positions.

7.15 Gearbox
Note: There are 2 different gearboxes for this product.
One is used with a cutting head and one is used with a
blade.

1239 - 001 - Repair instructions- 61

5. Remove the snap ring on the output shaft. 10. Tap the bevel gear against a wooden block to
disassemble the input shaft.

6. Remove the snap ring (B) on the input shaft.

11. Lift the output shaft to remove it.
B 12. Use a hot air gun to increase the temperature of the
D gear housing to approximately 140°C. Disassemble
the small ball bearing for the output shaft.
13. Disassemble the ball bearing and the gear wheel
from the shaft.

7. Remove the grease filter plug (C).

8. Remove the grease filter plug (D).
9. Use a hot air gun to increase the temperature of the
full bevel gear to approximately 110°C.

14. Disassemble the snap ring and remove the ball

bearing from the shaft.

62 - Repair instructions 1239 - 001 -

7.15.2 To assemble the bevel gear (543RBX) 5. Push out the output shaft into the gear housing.
1. Put the bevel gear and the output shaft together.

Note: Make sure that the ball bearings touch the

bottom of the gear housing.

6. Attach the ball bearings on the axle. Make sure that

the snap ring holds the ball bearings in position.

2. Put the gear wheel on the shaft.

3. Put the 2 ball bearings in position.
4. Increase the temperature of the bevel gear to
approximately 140°C.

7. Install the output shaft.

1239 - 001 - Repair instructions- 63

8. Put the input shaft in position with a pair of pliers. 11. Put grease into the gear through the grease filler cap
Make sure that the bearing touches the bottom. (C) until it comes out through the valve (D).

B
D

9. Put the snap ring (D) on the output shaft. 12. Assemble the cutting attachment and spray guards
in the opposite sequence to how they were
D disassembled.

7.15.3 To disassemble the bevel gear (553RBX)

1. Loosen the screw (A) and remove the splash guard.

D
10. Attach the snap ring (B) on the input shaft.

2. Remove the screw (B) and remove the plate (C).

3. Loosen the screws (D) and pull the gearbox from the
shaft.

64 - Repair instructions 1239 - 001 -

4. Remove the snap ring (E) 9. Disassemble the bearings from the output and input
shafts with a small bearing puller.
E

5. Remove the large snap ring that holds the ball

bearing on the input shaft.
6. Use a hot air gun to increase the temperature of the
full bevel gear to approximately 110°C.

7. Tap the bevel gear against a wooden block to

disassemble the input shaft.
8. Lift the output shaft to remove it.

1239 - 001 - Repair instructions- 65

7.15.4 To assemble the bevel gear (543RBK)
1. Put the bearings on the related shafts. Use a hot air
gun to increase the temperature of the bearings to
approximately 110°C.

2. Install the bearings with the sealed side out.

3. Use a hot air gun to increase the temperature of the
gearbox to approximately 110°C.
4. Install the output shaft. Make sure that the bearing
touches the bottom.
5. Install the input shaft. Make sure that the bearing
touches the bottom.
6. Install the snap ring (B) and (C). Make sure they are
correctly installed in their grooves.
7. Assemble the remaining parts in the opposite
sequence to how they were disassembled.

66 - Repair instructions 1239 - 001 -

 8 Troubleshooting
Start
The engine is not easy to start. The stop screw for the throttle does not operate correctly.
Blocked fuel filter.
Blocked fuel hose.
Air in fuel pipes.
Incorrect/unsatisfactory fuel.
The needle valve is defective.
The lever arm of the needle valve is damaged.
The lever arm of the needle valve does not operate correctly.
Blocked needle valve.
The needle valve is worn.
Object in the needle valve groove.

Idle speed (low speed)

The engine does not operate on idle speed. The stop screw for the throttle does not operate correctly.
Blocked fuel filter.
Blocked fuel hose.
Air in fuel pipes.
The carburetor is not attached correctly .
The lever arm of the needle valve does not operate correctly.
The idle speed is too low. Defective heat insulation seal.
The lever arm of the needle valve is damaged.
The lever arm of the needle valve is too high.
The lever arm of the needle valve does not operate correctly.
The needle valve is worn.
Object in the needle valve groove.
The idle speed does not become stable. The stop screw for the throttle does not operate correctly.
Blocked fuel filter.
Blocked fuel hose.
Air in fuel pipes.
Incorrect/unsatisfactory fuel.
The needle valve is defective.
The carburetor is not attached correctly .
The lever arm of the needle valve does not operate correctly.
The needle valve spring is not attached correctly.
The needle valve is worn.
Object in the needle valve groove.

1239 - 001 - Troubleshooting- 67

Idle speed (low speed)
The engine stops at idle speed. The stop screw for the throttle does not operate correctly.
Blocked fuel filter.
Blocked fuel hose.
Air in fuel pipes.
The needle valve is defective.
Defective heat insulation seal.
The lever arm of the needle valve is too high.
The lever arm of the needle valve does not operate correctly.
The needle valve spring is damaged.
The needle valve spring is not attached correctly.
The needle valve is worn.
Object in the needle valve groove.

High speed
Unsatisfactory performance at high speed. Blocked fuel filter.
Blocked fuel hose.
Air in fuel pipes.
Incorrect/unsatisfactory fuel.
The needle valve is defective.
The carburetor is not attached correctly.
The lever arm of the needle valve is damaged.
The lever arm of the needle valve does not operate correctly.
The needle valve spring is damaged.
The needle valve spring is not attached correctly.
The needle valve is worn.
Object in the needle valve groove.

Increase and decrease speed

The engine does not increase speed. Blocked fuel filter.
Blocked fuel hose.
Air in fuel pipes.
The needle valve is defective.
The carburetor is not attached correctly.
The lever arm of the needle valve is damaged.
The lever arm of the needle valve is too low.
The lever arm of the needle valve does not operate correctly.
The needle valve spring is not attached correctly.
Blocked needle valve.

68 - Troubleshooting 1239 - 001 -

Increase and decrease speed
The engine stops when the speed is de- The lever arm of the needle valve is too high.
creased.
The lever arm of the needle valve does not operate correctly.
The needle valve is worn.
Object in the needle valve groove.
The engine cannot increase speed. Defective heat insulation seal.

1239 - 001 - Troubleshooting- 69

 9 Technical data
543RBX 543RBK 553RBX
Engine
Cylinder displacement, cm3 40.1 50.6
Cylinder bore, mm 40.5 45.5
Stroke, mm 31.1 31.1
Idle speed, rpm 3000 2800
Recommended max speed, rpm 12000 13000
Max. engine output, according to ISO 8893,
1.47 @ 9000 2.3 @ 9500
kW @ rpm
Catalytic converter muffler No No
Ignition system
Spark plug NGK CMR7H-10 NGK CMR7H
Electrode gap, mm 0.9-1.0 0.6-0.7
Fuel and lubrication system
Fuel tank capacity, l/cm3 0.75 0.8
Carburetor
Type Walbro WT1102, Dia-
Walbro TEA-7, Diaphragm pump, butterfly
phragm pump, butter-
valve
fly valve
Weight
Without fuel, cutting attachment and guard,
11.4 11.5 12.1
kg
Sound levels1
Equivalent sound pressure level at the opera-
tor’s ear, measured according to EN ISO 99 103
11806 and ISO 22868, dB(A), min./max.
Vibration levels2
Equivalent vibration levels (ahv,eq) at handles, measured according to EN ISO 11806 and ISO 22867, m/s2
Equipped with Grass blade, grip/handle 4.4/3.6 5.3/4.3

1 Reported data for equivalent sound pressure level has a typical statistical dispersion (standard deviation) of 1
dB (A).
2 Reported data for vibration level has a typical statistical dispersion (standard deviation) of 1 m/s2.

70 - Technical data 1239 - 001 -

1239 - 001 - Technical data- 71
114 14 93-26

2019-09-27