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340, 345, 350
346XP, 351
Workshop manual
101 90 26-26
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Workshop manual
Husqvarna 340, 345, 346XP/G, 350, 351 /G
Contents
Introduction ...........................................................2
Safety regulations .................................................3
General instructions ...........................................3
Special instructions ............................................3
Special tools ..........................................................4
Technical data ....................................................... 6
Construction and function ................................... 8
Carburettor......................................................... 8
Troubleshooting..................................................10
Repair instructions .............................................12
Chain brake......................................................12
Silencer ............................................................14
Chain catcher................................................... 14
Stop switch.......................................................15
Stop switch – resistance measurement ...........15
Choke control................................................... 16
Throttle trigger..................................................17
Hand grip heater ..............................................18
Starter assembly ..............................................20
Starter cord ......................................................21
Recoil spring ....................................................21
Ignition module – testing ..................................22
Ignition module and flywheel............................23
Generator......................................................... 24
Centrifugal clutch .............................................26
Oil pump...........................................................28
Carburettor....................................................... 31
Carburettor – pressure testing .........................34
Carburettor – adjustment .................................36
Fuel tank ..........................................................38
Fuel hose .........................................................39
Piston and cylinder...........................................40
Decompression valve – pressure testing .........41
Cylinder – pressure testing ..............................43
Crankcase and crankshaft ...............................44
Crankshaft bearings......................................... 46
Repairing damaged threads.............................48
Guide bar bolts.................................................48
Fuel filter ..........................................................48
Appendix A, Carburettor – EPA models ...........49
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Introduction
Arrangement of the manual
This workshop manual can be used in two different
ways.
• To repair a specific sub-assembly on a chainsaw.
• To dismantle and reassemble a complete
chainsaw.
Repairing a specific sub-assembly
If a specific sub-assembly on the chainsaw needs
to be repaired:
1. Look up the page referring to the relevant subassembly.
2. Follow the instructions under the headings:
Removal/Dismantling
Cleaning and inspection
Refitting/Reassembly
Dismantling and reassembling the entire
chainsaw
If the entire chainsaw is to be dismantled, follow
the instructions under the heading “Removal/
Dismantling”.
Work through the manual and follow the instructions given in each section under the heading
“Removal/Dismantling”.
Troubleshooting
These pages describe the most common faults that
affect a chainsaw. They are divided into four
different groups with the most likely faults described first.
Repair instructions
The section that describes how to repair the
chainsaw consists of detailed, step-by-step instructions. It explains in detail the special tools, lubricants and bolt torques that are needed when
working on each component.
This workshop manual covers the following
chainsaw models:
340
345
350
351
351 G
346 XP
346 XPG
Then follow all the “Cleaning and inspection”
instructions in each section.
Working from the back of the manual, follow all the
instructions under the headings “Refitting/
Reassembly” in reverse order.
Each of the sections covering removal/dismantling
and refitting/reassembly include the relevant
lubrication instructions and bolt torques for each
stage of repair.
Construction and function
This chapter gives a simple description of the
chainsaw carburettor and its v arious parts.
2 – English
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Safety regulations
General instructions
This workshop manual gives detailed instructions
on how to troubleshoot, repair and test a chainsaw.
This section also describes the various safety
precautions that should be taken when carrying out
repairs.
The workshop manual has been written for personnel who are assumed to have general experience
of repairing and servicing chainsaws.
Workshops where chainsaws are repaired must be
equipped with safety equipment that meets local
regulations.
No-one should carry out repairs on a chainsaw
until they have read and understood the contents
of this workshop manual.
Chainsaws are type-approved to meet the relevant
safety legislation, but this only applies when the
saw is fitted with the cutting equipment specified in
the user’s manual. The fitting of any other equipment, or of accessories or parts that are not
approved by Husqvarna, could mean that the saw
no longer meets these safety requirements and the
person who carried out the work may be held
responsible for its non-conformance.
Special instructions
The fuel that is used in a chainsaw poses the
following hazards:
• The fuel and its fumes are toxic.
• May cause irritation to skin or eyes.
• May cause breathing difficulties.
• Highly flammable.
When using compressed air the air jet should
never be pointed at the body. Air can be forced into
the bloodstream and cause fatal injury.
Wear ear protection when testing saws.
After testing a saw do not touch the silencer until it
has cooled down. The silencer gets very hot and
you may burn yourself. Wear protective gloves
when working on the silencer.
The guide bar, chain and clutch cover (chain brake)
must be fitted before the saw is started. If not, the
clutch may come loose and cause injury.
Poor chain lubrication can result in failure of the
chain, which could cause serious or fatal injury.
In this workshop manual the following boxes
indicate where caution should be taken.
WARNING!
!
NOTE!
The warning text warns of the risk of
material damage if the instructions are
not followed.
The warning text warns of the risk
of personal injury if the instructions are not followed.
Take care to ensure that the spring inside the
starter assembly does not fly out and cause injury.
Wear eye protection. If the spring is under compression when the pulley is removed it could fly out
and cause injury.
Before removing the tensioning spring from the
chain brake, ensure that the brake is in the on
position, otherwise the spring may fly out and
cause injury.
After repair, the chain brake must be checked as
described on page 13.
Always consider the fire risk. A chainsaw can
produce sparks that could start a fire.
Inspect the chain catcher and replace it if it is
damaged.
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Special tools
1
4
2
5
3
6
9
7
10
11
8
12
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Special tools
13
16
14 15
17
18
Item Description Used for Order no.
1 Clutch tool Centrifugal clutch 502 54 16-01
2 Piston stop Locking crankshaft 502 54 15-01
3 Stop plate Locating intake gaiter 502 54 17-01
4 Fuel filter hook Withdrawing the fuel filter 502 50 83-01
5 Allen key For M5 bolts 502 50 18-01
6 Puller Frame bearing 504 90 90-02
7 Sleeve , sealing ring Removing flywheel 502 54 20-01
8 Mandrel, sealing ring Removing crankshaft 502 54 21-01
9 Cover plate Sealing during pressure testing 502 54 11-02
10 Pressure tester Connection to cylinder 503 84 40-02
11 Feeler gauge Adjusting ignition module 502 51 34-02
12 Clamp stand Clamping the saw 502 51 02-01
13 Pressure gauge Pressurisation during testing 502 50 38-01
14 Piston fitting kit Fitting piston 502 50 70-01
15 Test plug Checking ignition module 502 71 13-01
16 Rev counter Adjusting carburettor 502 71 14-01
17 Removal tool Removing crankshaft 502 51 61-01
18 Assembly pliers Fitting spark plug guard 502 50 06-01
19 a Assembly tool right-hand thread 502 70 45-06
19 b Assembly tool left-hand thread 502 70 45-07
19 c Assembly tool Sleeve 502 70 84-01
20 Stop plate Removing crankshaft 502 54 18-01
19 a
19 b
19 c
20
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Technical data
Displacement Cylinder bore Stroke Max power/speed
cm3/cubic inches Ø mm/Ø inches mm/inches kW/hp/rpm
340: 40.8 / 2.48 40.0 / 1.60" 32.5 / 1.28" 2.0/ 2.7 /9,000
345: 45.0 / 2.73 42.0 / 1.65" 32.5 / 1.28" 2.2/ 3.0 /9,000
346XP/G: 45.0 / 2.73 42.0 / 1.65" 32.5 / 1.28" 2.5/ 3.4 /9,600
350: 49.4 / 3.0 44.0 / 1.73" 32.5 / 1.28" 2.3/ 3.1 /9,000
351 /G: 49.4 / 3.0 44.0 / 1.73" 32.5 / 1.28" 2.3/ 3.1 /9,000
Spark plug gap Ignition system Air gap Carburettor type
mm/inches mm/inches
340: 0.5 / 0.02" FHP CD 0.3 / 0.012" Walbro HDA 154A (159A US only)
345: 0.5 / 0.02" FHP CD 0.3 / 0.012" Walbro HDA 154A (159A US only)
346XP/G: 0.5 / 0.02" FHP CD 0.3 / 0.012" Walbro HD A 154A (159A US only)
350: 0.5 / 0.02" FHP CD 0.3 / 0.012" Walbro HDA 154A (159A US only)
351 /G: 0.5 / 0.02" FHP CD 0.3 / 0.012" Walbro HD A 154A (159A US only)
Effective cutting length Chain speed at Chain pitch Drive link
cm/inches max power – revs mm/inches mm/inches
m/s – rpm
340: 30-48 / 12"-19" 17.3 / 9,000 8.25 / 0.325" 1.3 / 0.050" - 1.5 / 0.058"
345: 30-48 / 12"-19" 17.3 / 9,000 8.25 / 0.325" 1.3 / 0.050" - 1.5 / 0.058"
346XP/G: 30-48 / 12"-19" 18.5 / 9,600 8.25 / 0.325" 1.3 / 0.050" - 1.5 / 0.058"
350: 30-48 / 12"-19" 17.3 / 9,000 8.25 / 0.325" 1.3 / 0.050" - 1.5 / 0.058"
351 /G: 30-48 / 12"-19" 17.3 / 9,000 8.25 / 0.325" 1.3 / 0.050" - 1.5 / 0.058"
6 – English
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Technical data
rpm
Idling speed Engagement speed Max. speed Spark plug
rpm rpm rpm
340: 2,700 3,800 12,500 Bosch RCJ 7Y, NGK BPMR 7A
345: 2,700 3,800 12,500 Bosch RCJ 7Y, NGK BPMR 7A
346XP/G: 2,700 3,800 14,700 Bosch RCJ 7Y, NGK BPMR 7A
350: 2,700 3,800 13,000 Bosch RCJ 7Y, NGK BPMR 7A
351 /G: 2,700 3,800 13,000 Bosch RCJ 7Y, NGK BPMR 7A
GAS
Fuel tank capacity Oil pump capacity at Oil tank capacity Automatic oil pump
Litres/US pints 8,500 rpm, Litres/US pints
ml/min
340: 0.5 / 1.06 9 0.25 / 0.53 Yes
345: 0.5 / 1.06 9 0.25 / 0.53 Yes
346XP/G: 0.5 / 1.06 5 - 10 0.28 / 0.59 Yes
350: 0.5 / 1.06 5 - 10 0.25 / 0.53 Yes
351 /G: 0.5 / 1.06 5 - 10 0.28 / 0.59 Yes
Weight without bar and chain Weight with bar and chain Heated hand grips
kg / lbs kg / lbs
OIL
340: 4.7 / 10.4 5.5 / 12.1 345: 4.7 / 10.4 5.5 / 12.1 346XP: 4.8 / 10.6 5.6 / 12.2 346XPG: 4.8 / 10.6 5.6 / 12.2 Yes
350: 4.8 / 10.6 5.6 / 12.2 351: 4.8 / 10.6 5.6 / 12.2 351G: 4.8 / 10.6 5.6 / 12.2 Yes
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Construction and function
Carburettor
The carburettor consists of three sub-systems:
• The metering unit (A) which contains the jets
and the fuel control mechanism. This measures
out the right amount of fuel to suit the speed of
the saw and the power demand.
• The pump unit (C) pumps fuel from the tank to
the metering system inside the carburettor. One
side of the pump diaphragm is connected to the
crankcase and pulses as a result of pressure
changes in the crankcase. The other side of the
diaphragm sucks in the fuel.
The carburettor works in different ways depending
on the setting:
• Cold start mode
• Idling mode
• Part throttle mode
• Full throttle mode
• The mixing unit (B) consists of the choke,
diffuser jets and throttle valve. This is where the
air and fuel are mixed to create a flammable
mixture.
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In the cold start mode the choke valve (D) is
completely closed. This increases the vacuum in
the carburettor so that fuel is sucked through the
diffuser jets faster (E).
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Construction and function
In idling mode the throttle valve (F) is closed. Air is
sucked through an aperture in the throttle valve
and a small amount of fuel is supplied through the
diffuser jet (E).
In part throttle mode the throttle valve (F) is partially open. Fuel is supplied through the diffuser jets
(E).
In full throttle mode both valves are open and fuel
is supplied through all the diffuser jets (E).
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Troubleshooting
The various faults that can affect a chainsaw are divided into four groups. In each group the likely symptoms are given on the left and possible causes are listed on the right. The most likely faults are given first,
and so on.
Starting
Difficulty starting
Carburettor
leaking fuel
Flooding when
engine not
running
Idling (low rpm)
Will not idle
Idling too rich
Adjust L screw
Air filter blocked
Choke not working
Worn choke pivot
Worn choke valve
Fuel filter blocked
Fuel line blocked
Piston ring seized
Blocked impulse channel
Loose or faulty fuel pipe
Hole in diaphragm
Worn needle valve
Needle valve assemb ly stic king
Needle valve set too high
Leak in metering system (air
or fuel)
Loose cover on carburettor
pump side
Worn needle valve
Needle valve set too high
Needle valve assemb ly stic king
Adjust L screw
Leaking air intake hose (rubber)
Loose carburettor mounting bolts
Loose or faulty fuel hose
Fuel filter blocked
Fuel line blocked
Fuel tank vent blocked
Throttle valve pivot stiff
Throttle pushrod sticking
Defective throttle return spring
Bent throttle stop
Faulty diffuser jet
Adjust L screw
Worn needle valve
Needle valve set too high
Worn needle valve lever
Leaking control diaphragm/cover
plate
Needle valve assembly sticking
Idling (low rpm) (cont.)
Idles when L
screw closed
Idling uneven
L screw requires
constant
adjustment
Too much fuel at
idling
Worn needle valve
Leaking control diaphragm/
cover plate
Needle valve assemb ly sticking
Worn needle valve lever
Faulty diffuser jet
Fuel filter blocked
Fuel line blocked
Leaking air intake hose (rubber)
Loose carburettor mounting
bolts
Worn throttle valve pivot
Loose throttle valve screw
Worn throttle valve
Needle valve assembly
sticking
Leak in metering system (air
or fuel)
Metering system centre knob
is worn
Hole in diaphragm
Leaking control diaphragm/
cover plate
Crankcase leaking
Fuel line blocked
Needle valve set too high
Needle valve assemb ly sticking
Leak in metering system (air
or fuel)
Leaking control diaphragm/
cover plate
Faulty diffuser jets
Crankcase leaking
Needle valve set too high
Needle valve assemb ly sticking
Metering system damaged
Worn needle valve
Leaking control diaphragm/
cover plate
Metering system incorrectly
assembled
10 – English
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Troubleshooting
High rpm
Will not run
at full throttle
Low power
Will not
“four-stroke”
Adjust H screw
Blocked air filter
Blocked fuel tank vent
Blocked fuel filter
Fuel line blocked
Loose or damaged fuel hose
Impulse channel leaking
Impulse channel blocked
Loose cover on carburettor pump
side
Faulty pump diaphragm
Leaking air intake hose (rubber)
Loose carburettor mounting bolts
Needle valve set too low
Metering system damaged
Metering system incorrectly
assembled
Leaking control diaphragm/cover
plate
Needle valve assembly sticking
Blocked silencer
Adjust H screw
Blocked fuel tank vent
Blocked fuel filter
Impulse channel leaking
Impulse channel blocked
Loose cover on carburettor pump
side
Faulty pump diaphragm
Blocked air filter
Needle valve assembly sticking
Leak in metering system (air or fuel)
Metering system incorrectly
assembled
Loose diaphragm rivet
Hole in diaphragm
Leaking control diaphragm/cover
plate
Blocked fuel tank vent
Blocked fuel filter
Fuel line blocked
Loose or damaged fuel hose
Impulse channel leaking
Impulse channel blocked
Loose cover on carburettor pump
side
Faulty pump diaphragm
Leaking air intake hose (rubber)
Loose carburettor mounting bolts
Needle valve set too low
Leak in metering system (air or fuel)
Metering unit incorrectly
assembled
Loose diaphragm rivet
Hole in diaphragm
Leaking control diaphragm/cover
plate
Acceleration and retardation
Does not
accelerate
Engine stalls
when throttle
released
Over rich
acceleration
Adjust L screw
Adjust H screw
Blocked air filter
Blocked fuel tank vent
Blocked fuel filter
Fuel line blocked
Loose or damaged fuel hose
Impulse channel blocked
Loose cover on carburettor
pump side
Faulty pump diaphragm
Leaking air intake hose (rubber)
Loose carburettor mounting
bolts
Needle valve set too low
Metering system incorrectly
assembled
Needle valve assembly sticking
Faulty diffuser jets
Blocked silencer
Adjust L screw
Adjust H screw
Faulty pump diaphragm
Needle valve set too high
Needle valve assembly sticking
Faulty diffuser jets
Adjust L screw
Adjust H screw
Blocked air filter
Faulty pump diaphragm
Faulty diffuser jets
Troubleshooting methods
In addition to the faults described in the above
table, trouble shooting can be carried out on
specific components or sub-systems of the
chainsaw. The various procedures are
described in the relevant sections, as follows:
• Checking the operation of
the chain brake Page 13
• Measuring the resistance of
the stop plate Page 15
• Pressure testing the carburettor Page 34
• Pressure testing the decompression
valve Page 41
• Pressure testing the cylinder Page 43
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Repair instructions
Chain brake – dismantling
1
Unscrew the bolts and remov e the clutch co ver.
Disengage the chain brake before removing the
clutch cover.
Remove the chain and guide bar.
2
3
WARNING!
!
Remove the screws that hold the cover over the
chain brake spring.
4
Make sure the spring does not fly
out and cause injury. Wear eye
protection.
Turn the clutch cover over and use a screwdriver to
place pressure on the elbow joint and release the
chain brake.
12 – English
Place one hand over the spring, use a small
screwdriver to push the bottom end of the spring
and prise it upwards to release it.
Cleaning and inspection
Measure the thickness of the chain brake band. It
must be no less than 0.6 mm at any point.
min 0,6 mm
• Clean all parts carefully.
• Lubricate the elbow joint with grease.
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Repair instructions
Chain brake – reassembly
1
Bolt the elbow joint to the brake band and tighten
to a torque of 1–1.5 Nm.
Locate the elbow joint and connected brake band
in their recesses in the clutch cover. Lubricate the
recess for the spring with grease.
2
4
Fit the clutch cover in place and press the upper/
front corner while pushing the kickback guard
forward so that it engages in the clutch cover.
5
WARNING!
!
Grip the clutch cover in a vice. Compress the
spring with special tool 502 50 67-01 and push it
down with your thumb.
3
Screw the cover bac k in place o v er the chain br ak e
spring, tightening the screws to a torque of 1–1.5 Nm.
Make sure the spring does not fly
out and cause injury. Wear eye
protection.
Pull the kickback guard backw ards into the disengaged position. This increases the diameter of the
clutch brake band so that it can be pushed into place.
NOTE!
After completing the repair the chain
brake must be tested as described below.
Operating test:
The engine must be running during the test.
Guide bar length Height
13 - 20 inches 50 cm
• Hold the chainsaw over a firm surface. The
height of the guide bar above the surface is
given in the table above.
• Let go of the front handle and let the chainsaw
fall towards the surface.
• When the guide bar hits the surface the chain
brake must engage.
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Repair instructions
Silencer – removal
WARNING!
!
1
Remove the cylinder cover.
2
Model 351/G and 346XP/G.
Remove the lower bolt from the silencer support.
3
Do not touch the silencer until it
has cooled down, otherwise you
may burn yourself.
Silencer – refitting
1
If the saw is equipped with a spark arrestor mesh
this should be fitted first.
2
Fit the cooling plate, gasket and silencer onto the
cylinder. Also fit the silencer support to models
351/G and 346XP/G.
Tighten the bolt(s) to a torque of 8–10 Nm.
3
Fit the cylinder cover. If the cylinder cover is secured
with bolts, tighten them to a torque of 2–3 Nm.
4
On models 351/G and 346 XP/G, fit and tighten the
bottom bolt for the silencer support.
5
Run the saw for at least 1 minute, then retighten
the silencer to 8–10 Nm.
Unscrew the bolts.
Lift off the silencer.
Remove the gasket and cooling plate.
4
If the saw is fitted with a spark arrestor mesh this
must also be removed.
Cleaning and inspection
Clean the mating surfaces of the gasket, cooling
plate and cylinder.
• Check that there are no cracks or other defects
in the silencer.
• Check that the spark arrestor mesh is not
damaged.
Chain catcher – replacement
1
Unscrew the blade bolts and remove the chain and
guide bar.
2
Remove the chain catcher and replace it with an
aluminium chain catcher. It is important to replace
the chain catcher when it is worn because its job is
to stop the chain if it snaps.
• Check that the gasket is undamaged.
14 – English
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3
Refit the chain and guide bar.
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