Husqvarna K 760 OilGuard Instruction manual

HUSQVARNA CONSTRUCTION PRODUCTS
Workshop manual
K 760 & K 760 Cut-n-Break

2
1. LITERATURE 3
2. SPECIAL FUNCTIONAL COMPONENTS 4
3. COMPONENTS – ORIENTATION 5
4. DISMANTLING INTO BASIC MODULES 6
5. STARTER 10
6. IGNITION SYSTEM 13
7. FLYWHEEL 16
8. AIR FILTER 18
9. FUEL SYSTEM 19
10. CARBURETTOR 22
11. DECOMPRESSION VALVE 29
12. CYLINDER/PISTON 30
13. CRANKCASE 36
14. CLUTCH 41
15. CUTTING HEAD 44
16. WET SYSTEM 51
17. HANDLE 52
18. OILGUARD (OPTIONAL) 53
19. K 760 CUT-N-BREAK 54
20. TOOLS 59
CONTENTS Page
HUSQVARNA
K 760
K 760 Cut-n-Break
115 32 40-26

3
LITERATURE1
Workshop Manual
The workshop manual covers virtually all work
in the workshop that involves the K760 and
K760 Cut-n-Break. Some very simple and rather
obvious repair work has been omitted.
Outline
An introductory section with the title
“Dismantling into Basic Modules” shows how
the machine is dismantled into large component
units, for example, the starter, cutting arm, air
filter, etc.
The manual goes on to describes in detail
through the different chapter how work on the
basic modules should be carried out.
This arrangement means that as a mechanic,
at least until you have learnt the basic composi-
tion of the machine, you need to start with the
chapter “Dismantling into Basic Modules” to
then move on to the chapter covering the speci-
fic service work.
Layout – pictures and text
Besides the pictures and illustrations there is
generally two columns of text. The left-hand text
column is a concise and is suitable for experienced
mechanics, the right-hand column gives a more
detailed description and is targeted at mechanics
with less experience of repair work on the power
cutter.
Contents
The manual is divided into numbered chapters
together with chapter headings that are stated in
bold at the top of each page.
The list of contents also has page references to
the start of each chapter.
Spare parts
K760 and K760 Cut-n-Break
The folders include all spares for Husqvarna
K760 and K760 Cut-n-Break.
The folders contain complete exploded
drawings for the whole machine where the
location, spares number and appearance of
each component is easy to identify.
HUSQVARNA CONSTRUCTION PRODUCTS
Workshop manual
K 760 & K 760 Cut-n-Break
“Dismantling into Basic Modules”
“Cutting head” (Example)
115 32 40-26
IPL, K760 Cut-n-Break, 2009-11, 575 66 02-01
K760 Cut-n-Break
Reservdelar
Spare parts
Ersatzteile
Pieces de rechange
Piezas de repuesto
Ricambi
Peças sobresselente
HUSQVARNA CONSTRUCTION PRODUCTS
575 66 02-01
IPL, K760, 2009-12, 574 48 01-02
K760
Reservdelar
Spare parts
Ersatzteile
Pieces de rechange
Piezas de repuesto
Ricambi
Peças sobresselente
HUSQVARNA CONSTRUCTION PRODUCTS
574 48 01-02

SPECIAL FUNCTIONAL COMPONENTS
4
X-Torq®
This engine technology was introduced with
its predecessor K750 under the name Dual
Charge, now renamed to X-Torq.
In addition to the intake from the carbu-
rettor with fuel/air mix there are two chan-
nels for intake of fresh air; the upper chan-
nels as shown in the illustration. By directing
the fuel/air mix and the clean air in separate
flushing ducts in the cylinder, the ratios of
fuel mixed air and clean air can be controlled
to ensure that they vary in different phases of
the engine's work cycle.
Cleaner exhaust and better perfor-
mance
The amount of unburned hydrocarbons (HC)
is reduced by approximately 75 % compared
with a traditional design. The emission values
are now clearly under the provisions of
EPAII.
The effect is higher across the whole rev
range, and the torque in the lower rev range
is now considerably higher.
Carburettor
The carburettor has undergone many detail
improvements and a connection to the fuel
chamber has been added for air purge.
Air purge
The pump has a suction function and is con-
nected to the carburettor's fuel chamber. Air
purge empties the fuel chamber of any air
and tops up the fuel chamber with fuel.
With continued pumping any excess fuel is
returned to the tank.
Lower vibration levels
The air filter system and the carburettor are
mounted in the anti-vibration handle device,
which means lower handle vibrations due to
the larger mass (weight) in the handle device.
The carburettor's position in the anti-vibra-
tion section means the carburettor function is
more stable and there is less wear on the car-
burettor's moving parts.
New filter system
The centrifugal cleaning has been significantly
improved with a new flywheel and modified
design of the air intake. The plastic foam fil-
ter from the previous generation is now dis-
continued.
Friction Retarder
The front belt pulley has an inhibiting
mechanism which comes into effect at low
speeds on the cutting blade.
Torx – T27
Torx screw, with the dimension T27, is used
virtually throughout to simplify the service
process.
Note that the screws may have a smooth or
grooved underside.
2
Torx T27

COMPONENTS – ORIENTATION3
5
Components
1. Cutting blade
2. Blade guard
3. Handle for the blade guard
4. Front handle
5. Air filter cover
6. Cylinder cover
7. Starter handle
8. Starter
9. Combination spanner
10. Belt adjustment screw
11. Lock screws for belt adjustment
12. Rear belt guard
13. Fuel tank
14. Throttle control
15. Rear handle
16. Throttle trigger lock
17. Air purge
18. Decompression valve
19. Water valve with tool attachment
20. Water connector
21. Choke lever
22. Sight glass for fuel
23. Start throttle lock
24. Stop switch
5
4
1
23
6
78
9
10
11
13 12 14
19
20
21
15
16
17
18
24
23
22

Basic modules
This chapter shows how the machine is
built up of basic modules, for example,
the starter, carburettor, air filter system,
etc.
The purpose is to illustrate how you
can easily and effectively dismantle and
assemble the machine in its basic modules.
Service work on a component level, for
example, replacing the starter cord, is
described in detail in respective chapters.
Cutting head
1. Loosen the screws to the cutting head.
(Tightening torque when mounting
18–22 lbf·ft/25–30 Nm.)
2. Loosen the tension of the belt with the
adjuster screw.
3. Detach the hose clip.
4. Remove the screws to the cutting head.
Remove the front belt guard by pushing
it forward.
5. Detach the hose at the water valve.
Lift off the belt from the belt pulley and
remove the cutting head.
6. Loosen the rear belt guard's two screws.
(Tightening torque when mounting
6.6–8.1 lbf·ft/9–11 Nm.)
7. Remove the guard.
DISMANTLING INTO BASIC MODULES 4
6
Starter
1. Loosen the starter's 4 screws.
2. Remove the starter.
12
5
67
12 3
4

1
DISMANTLING INTO BASIC MODULES
4
7
Air filter
1. Loosen the guard's three screws and
remove the guard.
2. Loosen the two screws that hold
the filter bottom.
3. Lift up the filter bottom together with
the filter.
4. Press the filter out of the filter bottom.
Cylinder cover
1. Loosen the four screws on the cylinder
cover.
Press together the rubber seal's collar
so that the cylinder cover can be lifted
off.
2. NOTE! When reassembling the rubber
seal must be drawn up through the cover
and the collar then adjusted to fit
correctly against the cover.
Carburettor
1. The carburettor unit is attached to the
cylinder by a single screw. Loosen the
screw.
2. Lift out the carburettor unit. Detach
the petrol hose and the hose to the “air
purge” from the carburettor.
Tip: Tape the throttle control in the
full throttle position to improve access
to the throttle rod's attachment on the
throttle control.
3. Pull the throttle rod out of the con-
trol.
4. The entire carburettor unit can now be
lifted out.
12
34
2!
34
12

DISMANTLING INTO BASIC MODULES 4
8
Assembly
5. Hook the throttle rod into the valve
arm as illustrated. Lift the carburettor
unit into position and fit the fuel hose.
Press down the throttle rod into throttle
control with the help of a pair of pliers.
6. Align the carburettor's choke arm in
the blue choke control.
7. Fit the carburettor unit. Align the lug
on the flange with the cut-out on the
cylinder. Tighten the screw at the top.
Carburettor compartment
1. Tank venting
This is dismantled by angling the unit
backwards and then pulling it out the
tank.
2. Stop switch
This is secured by a screw in the carburet-
tor compartment.
3. Controls
The controls in the rear handle become
accessible for service once the carburettor
unit has been dismantled.
Air duct
Start by removing the starter, air filter
cover and cylinder cover.
1. Lower air duct
In order for reassembly to be correct,
note how the cable to the stop switch is
mounted in the air duct. Lift the cable
out of its attachment.
2. Engine's earth point
The engine's earth point to the stop
button is placed here.
3. Upper air duct
3.1 Detach the ignition cable at the spark
plug and lift the cable out of its attach-
ment in the cover.
5
1
3
2
6
7!
1
2
3.1

DISMANTLING INTO BASIC MODULES4
9
3.2. Dismantle the three screws on the air
duct cover.
3.3. Lift off the air duct cover.
Muffler
Dismantle the cutting head and the
starter.
1. Dismantle the four screws on the
muffler.
2. Dismantle the muffler.
Fit the gaskets correctly!
3. The insulated fibre gasket should lie
closest to the muffler.
4. Fit the heat shield.
5. The aluminium gasket should lie
against the cylinder.
The screws should be tightened to a
torque of 8.0–9.5 lbf·ft/11–13 Nm.
Vibration dampening
Some service work can be aided by split-
ting the machine by the vibration dampe-
ning element.
Dismantle the air filter unit, cylinder
cover and upper the air duct cover.
Dismantle the screw holding the carbu-
rettor. Dismantle the starter and the air
duct cover. Loosen the cable lug by the
ignition module and unscrew the cable
to the earth point. Pull off the water hose
by the valve.
The engine unit is attached to the
handle unit at three points with the vib-
ration dampening element in the form of
springs. Dismantle the screws located by:
1. The lower section on the flywheel side.
2. The base on the clutch side.
3. The handle loop next to the water
valve.
To gain access to the spring's inner
screw, Torx T27, the tool diameter must
be max. 5 mm. The combination spanner
fits.
1 2
345
123
3.2 3.3

STARTER 5
10
Replacing the starter cord
Dismantle the starter.
Eliminate the spring force from
the return spring
1. Pull out the starter cord approximately
12 in./30 cm. Hold the starter pulley
with your thumb and place the cord in
the cut-out on the starter pulley.
2. Let the starter pulley rotate slowly and
wind up the cord on the metal sleeve.
3. Lift off the cord from the starter
pulley.
Attach the new starter cord
The starter cord should be 45 in./
115 cm long and have a diameter of
.16 in./4 mm.
1. Insert one end of the cord from the
top through the hole in the starter pulley
and then out through the notch for the
cord. Pull out virtually the whole cord
length until sufficient cord remains to tie
a knot as illustrated.
2. Insert the other end through the cover
and on through the handle. Tie a double
knot as illustrated.
Loading the return spring
1. Fit the starter cord in the cut-out.
2. Wind the start cord 4 turns around the
hub and pull out the starter handle and
release so that the cord is wound into the
starter pulley. Repeat the procedure with
3 turns of cord around the hub.
Important check!
Check that the return spring does not act
as an end stop by extending the cord
fully. In this position it should be possible
to turn the starter pulley a least a further
half turn before the spring stops the
movement.
1
1
23
2
12

STARTER5
11
Spring cassette
WARNING!
Handling springs of this type constitutes
a major risk for eye injuries, especially
when you dismantle a cassette with a
broken spring!
Always wear protective glasses when
handling the spring cassette!
Dismantling
Dismantle both screws on the spring
cassette.
Press out both catches on the spring
cassette with a screwdriver.
Cleaning
Never take out the spring from the
cassette. If the spring is dirty it can be
blown sufficiently clean with compressed
air. Now apply a light oil on the spring.
Starter pulley
First eliminate the spring force as per the
previous page. Remove the centre screw
and lift off the starter pulley.
Clean the surfaces between the starter
pulley and the spring cassette.
Assembly
Lubricate the hub with grease (arrows).
Preferably also apply some grease around
the starter pulley hub so that the grease
seals against the spring cassette.
Align the starter pulley cut-out with the
end of the spring when assembling. Fit
the centre bolt.
The centre of the starter pulley
The spring in the starter pulley dampens
vibrations. The dust seal above has an O-
ring. The spacer sleeve around the centre
screw is the upper bearing point for the
starter pulley. Check that the spacer sleeve
has not fallen off during reassembly.

12
STARTER 5
Starter pawls
Function
In principle the starter pawls have two positions that are determined by the
centrifugal force generated by the rotation of the flywheel.
When the engine is at a standstill the springs push the starter pawls towards
the centre, which when starting then grip the starter pulley's metal sleeve.
As soon as the engine starts, the starter pawls are thrown out of the starter
pulley's centre to their outer positions.
Consequently it is important for the function that the springs are in full
working order and that the starter pawls do not jam. The starter pawls must
not be lubricated!
Inspection
Check that the springs are in full wor-
king order and that the starter pawls do
not jam. Dismantle and clean if necessary.
Dismantling/assembling
The starter pawls are fitted using a shoul-
der screw. Note the position of the
springs in relation to the flanges on the
flywheel so that they are fitted correctly.
NOTE! Do not forget the washer (A) that
should lie under the starter pawls against
the flywheel.
Assembly
It is important that the spring does not
get caught between the starter pawls and
the flywheel. The following method is
recommended when assembling:
1. Press the spring into position in the
flywheel.
2. Fit the washer.
3. Screw on the starter pawls.
4. Make the simplest of “special tools”:
Bend the end of a thin steel wire and use
this to pull the spring under the starter
pawls to the mounting on the opposite
side.
Fitting the starter
Do as follows so that the starter pawls
come into the right position against the
starter pulley sleeve: First pull out the
cord about a half meter. Keep this posi-
tion when the starter is set against the
machine and slowly release and the starter
pawls will take on the correct position.
Tighten the four screws on the starter to a
torque of 5–6.5 lbf·ft/7–9 Nm.
A
12
34

IGNITION SYSTEM6
13
Function
The ignition system is fully enclosed and has no moving
parts. It is insensitive to moisture and dirt. The design is
such that the ignition point does not need to readjustment.
Husqvarna K760 has integrated overspeed protection in the
electronic unit that limits the engine's speed to 9,300 rpm.
The ignition system consists of the primary coil (A) and
secondary coil (B) which are both surrounded by the iron
core (C). An electronic digital unit (D) manages the switch
function.
Current is generated in the primary coil when the fly-
wheel's permanent magnet passes the coil and has the voltage
sequence illustrated in the diagram below. (The dashed line
indicates the voltage that should be generated if the current
is not broken.)
The ignition point is determined by the electronic unit,
which sense the voltage variation in the primary coil and
breaks the current at the right level, at the same time the
engine piston is just below the upper turning point. At the
breaking instant the voltage in the primary coil rises from
5 V (volt) to approximately 200 V through induction. At the
same time a high voltage, approximately 20,000 volt, is
transformed in the secondary coil to the spark plug.
Electronic
circuit
breaker
STOP
control
Volts
+
-
0
Ignition
point
SN
SN
1�
�
1�
�
A�
�
D�
�
B�
�
C�
�
2�
�
2�
�
3�
�
3�
�
Spark plug
The spark plug's electrode gap should be
.02 in./0.5 mm.
The electrodes should be free of soot
deposits and oil. Brush clean with a wire
brush.
A convex centre electrode and a worn
side electrode impair the ignition charac-
teristics. Replace the spark plug.
Spark plug
The electrode gap scale should
be .02 in./0.5 mm.
Ignition module
The ignition module components are fully enclosed to withstand external
effects. Individual components cannot be replaced.
The ignition cable, the contact unit to the spark plug and the seal on the
ignition module can be replaced.
The ignition module requires no routine service measures. (However, the
distance to the flywheel magnet can be adjusted where necessary.)
Besides the connection to the spark plug there are two connections on the
ignition module. The arrow-marked flat pin connector connects to the stop
switch. The other is the power outlet for machines with OilGuard.
0.5 mm
.02 in.

IGNITION SYSTEM 6
14
Trouble shooting
Examine the ignition system first when
the engine does not start.
Check the ignition spark
Earth the spark plug against the cylinder
by using the spark plug socket to extend
the earth cable as the air duct prevents
direct earthing.
Move the stop button to the operating
position. Pull the starter handle as with
starting.
Do the following if no spark occurs.
Faulty spark plug
Replace the spark plug with the test spark
plug 502 71 13-01. If there is spark now
the spark plug is defective. Replace the
spark plug.
If there is no spark the next step is to
check the ignition lead.
Faulty ignition lead
1, 2. Pull up the rubber seal by the igni-
tion module and unscrew the ignition
lead from this.
3. Insert a pair of pointed pliers in spark
plug connection and pull out the spring
and cable end.
4. If the connection is defective, the igni-
tion lead can be shortened slightly. Make
a new hole in the cable with a awl and fit
the connection spring.
5. The adjoining simple connection can
be used to check that the ignition lead is
not broken. The battery is connected in
series with a test lamp.
Alternatively, a resistance measurement
can be made using a Ohm meter.
Damaged short-circuit cable
Check that the short-circuit cable is in
position. Examine the cable for signs of
wear or damage where it may have
reached the engine body and in doing so
create a short circuit.
Test the stop switch and the cable to
this from the ignition module with one
of the following methods.
502 71 13-01
1
45
23

IGNITION SYSTEM6
15
Replacing the ignition module
The ignition module is secured by two
screws to the engine body.
When assembling the new module, the
flywheel with magnets is turned towards
the ignition module.
Place air gap gauge (.01 in./0.3 mm)
502 51 34-02 against the magnets and fit
the new module in position.
The screws should be tightened to a
torque of 6.6–8.1 lbf·ft/9–11 Nm.
502 51 34-02
Removing the stop switch
1. Remove the cable lug and the screw.
2–4. Bend the control to the left with a
large screwdriver and pull the switch to
the right side first.
Mounting the stop switch
1. Press the switch to the snap lock.
2. Press in the right side.
3. Press in the left side to ensure the snap
fastener locks the switch. Fit the screw
and cable lug.
Test of short circuit cable and
stop switch
Try using a measuring instrument or the
following simple solution: Connect a
battery in series with a test lamp to the
short-circuit cable and engine body.
Observe the test lamp while testing the
function of the stop switch. With the
stop switch in operating position the
lamp must be out.
If the lamp is on – check first that the
short circuit cable insulation is not
damaged and is providing contact to the
engine body. Now check the stop switch.
1
3
1
2
4
2 3

16
FLYWHEEL 7
Removal
Unhook the springs and place
the start hooks in their outer
positions.
The arrows mark the place for
the tool below.
Tool 502 51 49-02
A special tool from Husqvarna is
required to dismantle and assemble the
flywheel. The tool fits virtual all fly-
wheels on Husqvarna power cutters.
Tool 502 51 49-02
The special tool is used to
dismantle and assemble the
flywheel.
Centre with socket
Place a 13 mm socket on the flywheel's
centre screw. Push aside the start hook's
springs so that they are not squeezed
between the socket and flywheel.
Centre with socket
Place a 13 mm socket on the
centre screw. Make sure the
springs do not get caught up.
Centre the tool
Choose a suitable screw, supplied with
the tool, and mount the plate.
Centre the tool
Fit the plate.
Remove the centre nut
Use the special tool's handle to lock the
flywheel rotation and remove the nut
and washer.
Remove the nut
Removal
Remove the starter and lower air duct.
The start hooks must be in “running
mode” to be able to mount the screws to
the tool below, marked by arrows.
Unhook the springs and place the start
hooks in their outer positions.
502 51 49-02

17
FLYWHEEL7
Check the keyway and key
Note that the key in the flywheel
is cast and can not be replaced.
If the key is damaged the fly-
wheel must be replaced.
Check the keyway and key
Note that the key in the flywheel is cast
and can not be replaced. If the key is
damaged the flywheel must be replaced.
As the ignition point is determined by
the position of the flywheel on the crank-
shaft, components must have exactly the
right placement in relation to each other.
Only the force of the centre nut is not
sufficient to hold the flywheel in the
right position.
Fit the flywheel
The crankshaft and the centre of the fly-
wheel must be free from grease when
assembling.
Align the key in the flywheel with the
keyway on the crankshaft. Fit the washer
and nut.
Tightening torque
18–22 lbf·ft/25–30 Nm
Use a torque wrench to tighten the nut.
Remove the tool and hook up the
springs on the start hooks.
Fit the flywheel
The crankshaft and the centre of
the flywheel must be free from
grease when assembling.
Align the key in the flywheel
with the keyway on the crank-
shaft. Fit the washer and nut.
Tightening torque
18–22 lbf·ft/25–30 Nm
Use a torque wrench to tighten
the nut.
Mount the screw press
Mount the screw press in the centre and
screw it down far enough to ensure it is
secure in the plate.
Mount the screw press
Press off the flywheel
Lock the outer socket with a wrench and
screw in the centre screw until the fly-
wheel releases.
Hint: If the flywheel is sitting very firm-
ly, you can knock lightly with a hammer
on the screw to the flywheel to release. At
the same time lift the machine slightly
from the base by the tool handle.
Press off the flywheel
Lock the socket and screw in the
centre screw.
18–22 lbf·ft/25–30 Nm

AIR FILTER 8
18
Function
Husqvarna Active Air Filtration is a filter system that sig-
nificantly improves the K760 model. The improved centrifugal
cleaning has now made the previous plastic foam filter obsolete.
1. The centrifugal cleaning is the first step in the air clea-
ning of the inlet air. The fins and inlet nozzle are newly designed
and the amount of dust per volume of air has been halved com-
pared to previous models.
The fins on the flywheel supply the cylinder with cooling air
while they are also the active part in the centrifugal cleaning of
the engine's inlet air. An inlet nozzle is fitted next to the fins on
the flywheel. The centrifugal force means that large particles do
not follow the curved air currents to the nozzle, but are thrown
to the outside of the nozzle. Only very small dust particles manage
to curve with the air currents to the inlet.
2. The paper filter now has a more dust absorbing surface
area compared to its predecessor K750. The distribution chamber
in front of the paper filter spreads the air flow evenly over the
filter surface.
3. Service filter's sole task is to prevent foreign objects from
entering the engine during service work. The service filter should
only be replaced if it is damaged.
Filter service
1. Centrifugal cleaning
The inlet duct should be inspected and any deposits removed in
connection with filter replacement. Dust from dry cutting is
blown clean using compressed air. Material from wet cutting nor-
mally needs to be scraped off mechanically.
Make sure the rubber seal on the upper air duct cover is intact
and that it is correctly fitted in the cylinder cover!
2. Paper filter
The paper filter must not be cleaned but replaced, whenever
necessary, with a new filter. The replacement frequency is highly
dependent on the material to be cut and if the cutting is to be
wet or dry. Change the filter when the machine starts to lose
power.
Observe extreme caution when the filter is removed to ensure
that no dust particles fall down through the service filter.
Removal of waste and cleaning of the gasket around the service
filter is best done using a vacuum cleaner.
Also blow out the dust collected in the distribution chamber.
3. Service filter
The service filter only needs replacing if damaged.
2
3
115 32 40-26
1

19 115 32 40-26
FUEL SYSTEM9
Fuel filter
Dismantle the filler cap.
Catch the fuel hose with the
help of tool 502 50 83-01.
Fuel filter
Dismantle the filler cap and pull out the
section holding the filler cap in position
when fuelling.
Catch the fuel hose with the help of tool
502 50 83-01.
Pull out the hose a little through the
tank fill hole and pull out the fuel filter.
Check that the filter is not cracked or in
any other way defective. Fouled filters
must not be cleaned but replaced with
new ones. First lift up the metal ring
whereupon the hose can be pulled off the
filter.
If the filter is heavily fouled, this may be
due to the machine being filled with a
contaminated fuel. Drain the fuel and
filter when refilling.
Pull out the fuel filter. Check
that the filter is not cracked or
in any other way defective.
Fouled filters are replaced with
new ones.
Heavily fouled filters can be due
to fuelling with contaminated
fuel. Check and filter the fuel if
necessary.
Fuel hose
Pressure tester 501 56 27-01
Use the pressure tester 501 56 27-01 to
test the tightness of the fuel hose.
The pressure tester is supplied with an
adapter for small hose sizes, this should
be used on the fuel hose. Make the hose
between the adapter and the pressure
tester as short as possible.
Fuel hose
Pressure tester
Use the pressure tester to test
the tightness of the fuel hose.
Connect the adapter to the
pressure tester with a short hose.
Pressure test the fuel hose
Pump up the pressure to approximately
7 psi/50 kPa. A falling pressure indicates
that the fuel hose leaks, the connection
to the carburettor leaks or the carburet-
tor is defective.
Pressure test the fuel hose
Pump up the pressure to
approximately 7 psi/50 kPa.
Move to the next test if the
pressure drops.
501 56 27-01
502 50 83-01
Exclude the fuel hose as the
cause of leakage
Remove the carburettor unit. Plug the
hose by the carburettor and redo the
pressure test. If the hose is in tact, the
carburettor must be checked.
Exclude the fuel hose as
the cause of leakage
Remove the carburettor unit.
Plug the hose by the carburettor
and redo the pressure test.

20
Filter – functional test
Pull off the rubber hose with the sintered
filter. Blow through the hose and note
whether the air can pass through slowly.
Filter replacement
A clogged filter should not be blown
clean but replaced. Use a pin punch to
push out the filter out of the hose.
Push in a new filter.
Filter - functional test
Observe whether the air can
slowly pass through the filter.
Filter replacement
Clogged filters should not be
blown clean but replaced.
FUEL SYSTEM 9
Tank venting
The tank vent has a non-return valve that permits air to enter the tank, but
prevents fuel from running out. The sintered metal filter permits air to pass
slowly.
Fault indication
Blocked tank vent is shown as follows: As the fuel tank is emptied during use
an underpressure is created in the tank, which reduces the fuel supply – the
machine lacks power. When filler cap is opened air suction is audible.
Changing the fuel hose
Loosen the cable lug to the stop switch to gain better access to the fuel hose.
Remove the hose from the tank at the same time as it is fed down through the
hole in the carburettor compartment
little by little.
The new hoses is fed down into the tank from the carburettor compartment.
Feed down the hose by hand or with the help of a pair of pliers. Greasing the
hoses facilitates assembly.
Note how the fuel hose is suspended on the tank unit when assembling.
The snap lock for the hose holder can be opened with a small screwdriver
from the outside of the tank unit.
Do not forget to refit the cable lug on the stop switch!
Dismantling
The carburettor unit must be dismantled
to gain access to the tank vent.
Remove the choke control.
Press the air vent unit backwards and
push it up with some pliers.
Dismantling
Dismantle the carburettor unit
and choke control.
Press up the air vent unit with a
pair of pliers.