Stihl SR 430 User manual

STIH)
STIHL SR 430, 450 2009-06

1SR 430, SR 450
q
© ANDREAS STIHL AG & Co. KG, 2009
RA_454_00_01_01
1. Introduction and
Safety Precautions 3
1.1 Introduction 3
1.2 Safety Precautions 4
2. Specifications 5
2.1 Engine 5
2.2 Fuel System 5
2.3 Ignition System 5
2.4 Tightening Torques 6
3. Troubleshooting 8
3.1 Rewind Starter 8
3.2 Blower 9
3.3 Ignition System 10
3.4 Carburetor 12
3.5 Engine 15
4. Engine 16
4.1 Muffler / Spark
Arresting Screen 16
4.2 Leakage Test 17
4.2.1 Preparations 17
4.2.2 Vacuum Test 18
4.2.3 Pressure Test 18
4.3 Oil Seals 19
4.4 Shroud 19
4.5 Engine 20
4.6 Cylinder / Crankshaft 22
4.7 Bearings / Crankshaft 25
4.8 Piston 26
4.8.1 Piston Rings 29
5. Ignition System 30
5.1 Ignition Timing 30
5.2 Ignition Module 30
5.3 Testing
the Ignition Module 32
5.4 Spark Plug Boot 33
5.5 Flywheel 34
5.6 Short Circuit Wire 35
5.6.1 Testing 35
5.6.2 Removing and
Installing 35
5.6.3 Ground Wire 38
5.7 Ignition System
Troubleshooting 39
6. Rewind Starter 42
6.1 General 42
6.2 Starter Cover 42
6.3 Pawl 42
6.4 Rope Rotor 43
6.5 Starter Rope / Grip 44
6.6 Tensioning the
Rewind Spring 45
6.7 Replacing the
Rewind Spring 46
7. Servicing the
AV System 48
7.1 AV Springs at Rear
of Backplate 48
7.2 AV Springs at Bottom
of Backplate 49
7.3 AV Springs on
Backplate, Metering
Unit, SR 450 49
7.4 Stop Buffer on Filter
Housing 50
7.5 Stop Buffer on Shroud 50
8. Control Levers 51
8.1 Switch Positions 51
8.2 Setting Lever 51
8.3 Throttle Trigger/
Interlock Lever 52
8.4 Valve Lever 55
8.5 Metering Lever,
SR 450 56
8.5.1 Adjusting the Cable 57
9. Fuel System 58
9.1 Air Filter 58
9.2 Baffle 58
9.3 Air Guide Shroud 59
9.4 Filter Housing 59
9.5 Removing and Installing
the Carburetor 62
9.5.1 Leakage Test 63
9.6 Servicing
the Carburetor 64
9.6.1 Metering Diaphragm 64
9.6.2 Inlet Needle 65
9.6.3 Fixed Jet 66
9.6.4 Pump Diaphragm 66
9.6.5 Throttle Lever 67
9.6.6 Rotary Knob 68
9.6.7 Adjusting Screws 69
9.7 Adjusting the
Carburetor 70
9.7.1 Basic Setting 70
9.7.2 Standard Setting 71
9.8 Throttle Cable 72
9.8.1 Adjusting the Throttle
Cable 72
9.9 Spacer Flange 73
9.10 Tank Vent 74
9.10.1 Testing 74
9.10.2 Removing and
Installing 75
9.10.3 Manual Fuel Pump 75
9.11 Fuel Intake 76
9.11.1 Pickup Body 76
9.11.2 Fuel Hoses 77
9.11.3 Connector 79
9.12 Fuel Tank 80
9.12.1 Fuel Tank Cap 81
Contents

2SR 430, SR 450
Contents
10. Blower and Metering
Attachment 82
10.1 Container, SR 430 82
10.2 Container, SR 450 83
10.3 Metering Unit, SR 450 84
10.4 Cable, SR 450 87
10.5 Pressure Pump 89
10.6 Blower Wheel 90
10.7 Blower Housing,
SR 430 91
10.8 Blower Housing,
SR 450 95
10.9 Nozzle / Valve 98
10.9.1 Nozzle 98
10.9.2 Valve 99
10.10 Blower Tube 101
10.10.1 Pleated Hose 101
10.10.2 Elbow 101
10.10.3 Hoses 102
11. Backplate 103
11.1 Backplate, SR 430 103
11.2 Backplate, SR 450 103
11.3 Harness 105
11.4 Back Padding 106
12. Special Servicing
Tools 107
13. Servicing Aids 109

3SR 430, SR 450
1. Introduction and Safety Precautions
1.1 Introduction
This service manual contains
detailed descriptions of all the repair
and servicing procedures specific to
this power tool.
You should make use of the
illustrated parts lists while carrying
out repair work. They show the
installed positions of the individual
components and assemblies.
Refer to the latest edition of the
relevant parts list to check the part
numbers of any replacement parts.
A fault on the machine may have
several causes. To help locate the
fault, consult the chapter on
"Troubleshooting" and the
"STIHL Service Training System"
for all assemblies.
Refer to the “Technical Information”
bulletins for engineering changes
which have been introduced since
publication of this service manual.
Technical information bulletins also
supplement the parts list until a
revised edition is issued.
The special tools mentioned in the
descriptions are listed in the chapter
on "Special Servicing Tools" in this
manual. Use the part numbers to
identify the tools in the
"STIHL Special Tools" manual. The
manual lists all special servicing
tools currently available from
STIHL.
Symbols are included in the text and
pictures for greater clarity.
The meanings are as follows:
In the descriptions:
NAction to be taken as shown in
the illustration above the text
– Action to be taken that is not
shown in the illustration above
the text
In the illustrations:
APointer
aDirection of movement
@4.2 =Reference to another
chapter, i.e. chapter 4.2
in this example.
Service manuals and all technical
information bulletins are intended
exclusively for the use of properly
equipped repair shops. They must
not be passed to third parties.
Preparations for servicing
Always use original STIHL
replacement parts.
They can be identified by the STIHL
part number, the {logo
and the STIHL parts symbol K
This symbol may appear alone on
small parts.
Storing and disposing of oils
and fuels
Collect fuel or lubricating oil in a
clean container and dispose of it
properly in accordance with local
environmental regulations.

4SR 430, SR 450
1.2 Safety Precautions
If the machine is started up in the
course of repairs or maintenance
work, observe all local and country-
specific safety regulations as well
as the safety precautions and
warnings in the instruction manual.
Gasoline is an extremely flammable
fuel and can be explosive in certain
conditions.
Always wear suitable protective
gloves for operations in which
components are heated for
assembly or disassembly.
Improper handling may result in
burns or other serious injuries.
Do not smoke or bring any fire,
flame or other source of heat near
the fuel. All work with fuel must be
performed outdoors only. Spilled
fuel must be wiped away
immediately.
Always perform leakage test after
working on the fuel system and the
engine.
Always replace damaged parts.
Check disassembled parts for wear
or damage before re-installing –
replace as necessary.
Run the machine only with the
shroud mounted in position – there
is otherwise a risk of injury from the
flywheel and a risk of engine
damage due to overheating.
The chapter on tightening torques
lists all machine components that
have to be tightened to a specific
torque. The specifications must be
maintained when tightening down
screws, nuts and other fasteners in
all the procedures described in this
service manual.
Fuel system – hose barb
connectors
Pull off or push on fuel hoses in line
with the connector, preferably by
hand, to ensure the tightness of the
fuel system.
Avoid damaging the hose barb
– do not use sharp-edged pliers,
screwdrivers, etc.
Do not cut open fuel hoses with a
knife or similar tool.
Do not re-use fuel hoses after
removal. Always install new hoses
– fuel hoses can be overstretched
during removal.
Install new fuel hoses either dry or
with the aid of STIHL press fluid,
b13.
Other press fluids are not approved
and may result in damage to the fuel
hoses.
Coat the ends of the hoses and the
connectors with STIHL press fluid
and then push the new hoses on to
the hose barbs, b13.

5SR 430, SR 450
2. Specifications
2.1 Engine
SR 430 SR 450
Displacement: 63.3 cm363.3 cm3
Bore: 48.0 mm 48.0 mm
Stroke: 35.0 mm 35.0 mm
Engine power to ISO 7293: 2.9 kW (3.9 bhp) 2.9 kW (3.9 bhp)
Maximum permissible engine speed
(with nozzle)
6,800 rpm 6,800 rpm
Idle speed: 3,000 rpm 3,000 rpm
Crankcase leakage test
at gauge pressure: 0.5 bar
under vacuum: 0.5 bar
2.2 Fuel System
Carburetor leakage test at
gauge pressure:
0.8 bar
Operation of tank vent at
gauge pressure: 0.5 bar
Fuel: as specified in instruction
manual
2.3 Ignition System
Air gap between ignition
module and fanwheel: 0.15...0.30 mm
Spark plug (resistor type): NGK BPMR 7 A
Bosch WSR6F
Electrode gap: 0.5 mm

6SR 430, SR 450
2.4 Tightening Torques
DG and P (Plastoform) screws are used in polymer and light metal components. These screws form a
permanent thread when they are installed for the first time. They can be removed and installed as often as
necessary without impairing the strength of the screwed assembly, providing the specified tightening torque is
observed.
For this reason it is essential to use a torque wrench.
Fastener Thread size For component Torque Remarks
Nm
Screw P 5x18 Shroud/blower housing 4.0 2)
Screw P 4x12 Cover/housing 2.0
Screw P 5x18 Cover/inner handle molding 2.0
Screw P 5x18 Antistatic/blower housing 4.0
Screw P 5x25 Pressure pump/blower housing 3.0
Screw M 5x21 Filter cover/filter housing 4.0
Screw P 5x18 Filter housing/blower housing 4.0
Nut M 5 Filter housing/carburetor/baffle 3.5
Screw P 6x25 Blower housing/bearing plug 6.0
Screw P 5x18 Blower housing, outer/inner 4.0
Screw D 6x32 Blower housing, inner/engine pan 12.0 3)
Screw D 6x32 Blower housing, inner/cylinder 12.0 3)
Nut M 10x1 Blower wheel/crankshaft/nut 30.0
Screw P 5x18 Housing/blower housing 4.0
Screw P 4x19 Handle molding, outer/inner 1.5
Screw P 6x21.5 Handle molding/blower tube 4.0
Screw P 6x25 Lever/inner handle molding 4.0
Screw M 4x9.6 Exhaust pipe/muffler 4.0
Screw M 6x28 Engine pan/cylinder, stage 1 4.0 3), 5)
Screw M 6x28 Engine pan/cylinder, stage 2 12.0 3)
Screw P 5x18 Air guide shroud/blower housing 4.0
Screw P 4x19 Detent spring/inner handle molding 1.5
Screw P 6x25 Backplate/bearing plug 6.0
Screw P 6x25 Backplate/tank housing 6.0
Screw P 6x25 Backplate/bracket 6.0
Screw P 5x14 Back padding/backplate 2.5
Screw M 5x18 Muffler/cylinder, top, gasket 8.0 3)
Screw M 5x18 Muffler/cylinder, bottom 8.0 3)
Screw P 6x21.5 Hose clamp/blowing attachment 1.5
Nut M 8x1 Flywheel/crankshaft 20.0 4)
Screw P 5x18 Strainer/blower housing 3.0
Screw M 5x18 Starter cover/shroud/engine pan 6.0 3)
Screw M 5x18 Starter cover/shroud/cylinder 6.0 3)
Screw P 4x12 Shaft/rotary shutter 2.5

7SR 430, SR 450
Fastener Thread size For component Torque Remarks
Nm
M 14x1.25 Spark plug 25.0
Screw M 5x20 Ignition module/engine pan 6.0 1)
Screw M 5x20 Spacer flange/cylinder 6.0 3)
Remarks:
1) Micro-encapsulated with washer
2) Anti-friction coating
3) Binding head screw with anti-friction coating
4) Degrease joint and mount oil-free
5) Seal components with Dirko HT red sealant
Use the following procedure when refitting a DG or P screw in an existing thread:
Place the screw in the hole and rotate it counterclockwise until it drops down slightly.
Tighten the screw clockwise to the specified torque.
Coat micro-encapsulated screws with medium-strength threadlocking adhesive before re-installing.
This procedure ensures that the screw engages properly in the existing thread and does not form a new thread
and weaken the assembly.
Power screwdriver setting for polymer: DG and P screws max. 500 rpm
Do not use an impact wrench for releasing or tightening screws.
Do not mix up screws with and without binding heads.

8SR 430, SR 450
3. Troubleshooting
3.1 Rewind Starter
Condition Cause Remedy
Starter rope broken Rope pulled out too vigorously as
far as stop or over edge, i.e. not
vertically
Fit new starter rope
Normal wear Fit new starter rope
Starter rope does not rewind Very dirty or corroded Clean or replace rewind spring
Insufficient spring tension Check rewind spring and increase
tension
Rewind spring worn Fit new rewind spring
Starter rope cannot be pulled out
far enough
Rewind spring overtensioned Check rewind spring and reduce
tension
Starter rope can be pulled out
almost without
resistance (crankshaft does not
turn)
Guide peg on pawl or pawl itself is
worn
Fit new pawl
Pawl spring fatigued Fit new pawl spring
Starter rope is difficult to pull or
rewinds very slowly
Starter mechanism is very dirty Thoroughly clean complete starter
mechanism
Lubricating oil on rewind spring
becomes viscous at very low
outside temperatures (spring
windings stick together)
Coat rewind spring with standard
solvent-based degreasant
(containing no chlorinated or
halogenated hydrocarbons), then
pull the rope carefully several times
until normal action is restored

9SR 430, SR 450
3.2 Blower
Always switch off the engine before working on the blower.
Condition Cause Remedy
Blower does not blow Blower wheel loose Tighten down nut on blower wheel
firmly
Blower wheel blocked Clean blower housing
Blower wheel worn or too many
blades broken
Fit a new blower wheel

10 SR 430, SR 450
3.3 Ignition System
Exercise extreme caution while
carrying out maintenance and
repair work on the ignition system.
The high voltages which occur can
cause serious or fatal accidents.
Condition Cause Remedy
Engine runs roughly, misfires,
temporary loss of power
Spark plug boot is loose Press boot firmly onto spark plug
and fit new spring if necessary
Spark plug sooted, smeared with oil Clean the spark plug or replace if
necessary.
Fuel/oil mixture
– too much oil
Use correct mixture of fuel and oil
Incorrect air gap between ignition
module and flywheel
Set air gap correctly
Flywheel shows signs of
damage (e.g. scores) or pole shoes
have turned blue
Install new flywheel
Ignition timing out of adjustment,
flywheel warped, key in flywheel
sheared
Install new flywheel
Flywheel magnetization weak –
pole shoes have turned blue
Install new flywheel
Irregular spark Check operation of stop switch and
ignition module.
Faulty insulation or break in ignition
lead or short circuit wire. Check
ignition lead/ignition module and
replace ignition module if
necessary.
Check operation of spark plug.
Clean the spark plug or replace if
necessary.
The carburetor or engine may also be the cause of poor engine running behavior

11SR 430, SR 450
Condition Cause Remedy
No spark Spark plug faulty Install new spark plug
Faulty insulation or short in short
circuit wire
Check short circuit wire for short
circuit to ground
Break in ignition lead or insulation
damaged
Check ignition lead, replace ignition
module if necessary
Ignition module faulty Install new ignition module

12 SR 430, SR 450
3.4 Carburetor
Condition Cause Remedy
Carburetor floods
– engine stalls
Inlet needle not sealing
– Foreign matter between valve
seat and sealing cone or sealing
cone worn
Remove and clean the inlet needle,
clean the carburetor
Inlet control lever sticking on
spindle
Clean the inlet control lever or
replace if necessary.
Helical spring not located on nipple
of inlet control lever
Remove the inlet control lever and
refit it correctly
Perforated disc on metering
diaphragm is deformed and
presses constantly against the inlet
control lever
Fit a new metering diaphragm
Poor acceleration Setting of low speed screw (L) too
lean
Check basic carburetor setting,
correct if necessary
Setting of high speed screw (H) too
lean
Check basic carburetor setting,
correct if necessary
Inlet needle sticking to valve seat Remove inlet needle, clean and
refit
Diaphragm gasket leaking Fit new diaphragm gasket
Metering diaphragm damaged or
shrunk
Fit a new metering diaphragm
Spacer flange damaged Install new spacer flange

13SR 430, SR 450
Condition Cause Remedy
Engine will not idle, idle speed too
high
Throttle shutter opened too wide by
idle speed screw (LA)
Reset idle speed screw (LA)
correctly
Oil seals/engine leaking Seal or replace oil seals/engine
Throttle shutter stiff or torsion
spring on throttle shaft fatigued or
broken
Free off throttle shaft or install new
carburetor
Engine stops while idling Idle jet bores
or ports blocked
Clean the carburetor
Setting of low speed screw (L) too
rich or too lean
Reset low speed screw (L)
correctly
Setting of idle speed screw (LA )
incorrect – throttle shutter
completely closed
Reset idle speed screw (LA)
correctly

14 SR 430, SR 450
Condition Cause Remedy
Engine speed drops quickly under
load – low power
Air filter dirty Clean air filter or replace if
necessary
Throttle shutter not opened fully Check throttle cable
Tank vent faulty Replace tank vent
Fuel pickup body dirty Install new fuel pickup body
Fuel strainer dirty Clean fuel strainer in carburetor,
replace if necessary
Leak in the fuel suction hose Install new fuel suction hose
Setting of high speed screw (H) too
rich
Check basic carburetor setting,
correct if necessary
Main jet bores or ports blocked Clean or replace the carburetor
Pump diaphragm damaged or
fatigued
Fit new pump diaphragm

15SR 430, SR 450
3.5 Engine
Always check and, if necessary,
repair the following parts before
looking for faults on the engine:
- Air filter
- Fuel system
- Carburetor
- Ignition system
Condition Cause Remedy
Engine does not start easily, stalls
at idle speed, but operates normally
at full throttle
Oil seals in crankcase damaged Replace the oil seals
Engine leaking or
damaged (cracks)
Seal or replace the engine
Seal on engine pan leaking Re-seal the engine pan
Engine does not deliver full power
or runs erratically
Muffler / spark arresting screen
carbonized
Clean the muffler (inlet and
exhaust), replace spark arresting
screen, replace muffler if necessary
Air filter dirty Replace air filter
Tank vent faulty Check the tank vent and replace if
necessary.
Fuel suction hose kinked or torn Fit new hose or position it free from
kinks
Piston rings worn Fit new piston rings
Engine overheating Insufficient cylinder cooling. Air
outlets on blower housing blocked
or cooling fins on cylinder very dirty
Thoroughly clean all cooling air
openings and the cylinder fins

16 SR 430, SR 450
4. Engine
4.1 Muffler / Spark Arresting
Screen
Always check and, if necessary,
repair the fuel system, carburetor,
air filter and ignition system before
looking for faults on the engine.
– Troubleshooting, b3.5
– Remove the shroud, b4.4
:Take out the screws (arrows).
:Remove the muffler (1).
:Remove the gasket (1).
0002RA002 TG
1
0002RA003 TG
1
Installing
:Inspect and clean the sealing
faces (arrows), b13
– Insert the screws through the
upper holes in the muffler.
:Push the gasket (1) over the
screws – the gasket is held in
position.
– Carefully place the muffler (1) in
position.
:Check the position of the gasket
and fit the screws (2).
0002RA006 TG0002RA007 TG
1
0002RA008 TG
2
2
1
– Fit the screws (2)
– do not tighten down yet.
:Fit the screw (1).
– Tighten down screws (1) and (2)
firmly.
Spark arresting screen
(country-specific option)
:Take out the screws (1) and
remove the exhaust pipe (2).
0002RA009 TG
2 2
1
0002RA004 TG
1
2
1

17SR 430, SR 450
:Remove the spark arresting
screen (1).
– Clean the spark arresting screen
with bushing (1) or replace if
necessary.
– Reassemble in the reverse
sequence.
– Fit the shroud, b4.4
4.2 Leakage Test
Defective oil seals and gaskets or
cracks in castings are the usual
causes of leaks. Such faults allow
supplementary air to enter the
engine and upset the fuel-air
mixture.
This makes adjustment of the
prescribed idle speed difficult, if not
impossible.
Moreover, the transition from idle
speed to part or full throttle is not
smooth.
Always perform the vacuum test
first and then the pressure test.
The engine can be checked
thoroughly for leaks with the pump
0000 850 1300.
0002RA005 TG
1
4.2.1 Preparations
– Remove the shroud, b4.4
– Pull off the spark plug boot
vertically.
:Unscrew the spark plug (1).
– Set the piston to top dead center.
This can be checked through the
spark plug hole.
:Fit the spark plug (1) and tighten
it down firmly.
:Loosen the screws (arrows).
:Pull the muffler (1) out a little.
0002RA010 TG
1
0002RA011 TG
1
:Fit the sealing plate (1)
0000 855 8106 between the
cylinder exhaust port and muffler
and tighten down the screws
moderately.
The sealing plate must completely
fill the space between the two
screws.
– Remove the carburetor, b9.5
Check that the gasket (1) is in
position.
:Fit the test flange (1)
5910 850 4200.
0002RA012 TG
1
0002RA013 TG
1
0002RA014 TG
1

18 SR 430, SR 450
:Fit the nuts (arrows) and tighten
them down firmly.
4.2.2 Vacuum Test
Oil seals tend to fail when subjected
to a vacuum, i.e. the sealing lip lifts
away from the crankshaft during the
piston's induction stroke because
there is no internal counterpressure.
A test can be carried out with pump
0000 850 1300 to detect this kind of
fault.
:Connect pressure hose (1) of
pump 0000 850 1300 to the
nipple (arrow).
0002RA015 TG0002RA016 TG
1
:Push ring (1) to the left.
:Operate the lever (2) until the
pressure gauge (arrow) indicates
a vacuum of 0.5 bar.
If the vacuum reading remains
constant, or rises to no more than
0.3 bar within 20 seconds, it can be
assumed that the oil seals are in
good condition.
However, if the pressure continues
to rise (reduced vacuum in the
engine), the oil seals must be
replaced, b4.3.
– After finishing the test, push the
ring to the right to vent the pump.
– Continue with pressure test,
b4.2.3
1
2
0002RA017 TG
4.2.3 Pressure Test
Carry out the same preparations as
for the vacuum test, b4.2.2
– Always carry out the pressure
test after the vacuum test,
b4.2.2
:Connect pressure hose (1) of
pump 0000 850 1300 to the
nipple (arrow).
:Push ring (1) to the right.
:Operate the lever (2) until the
pressure gauge (arrow) indicates
a pressure of 0.5 bar. If this
pressure remains constant for at
least 20 seconds, the engine is
airtight.
– If the pressure drops, the leak
must be located and the faulty
part replaced.
0002RA016 TG
1
1
2
0002RA018 TG

19SR 430, SR 450
To find the leak, coat the suspect
area with oil and pressurize the
engine. Bubbles will appear if a leak
exists.
– After finishing the test, push the
ring to the left to vent the pump –
disconnect the hose.
– Remove the test flange.
– Install the carburetor, b9.5
– Loosen the screws on the muffler
and pull out the sealing plate.
– Tighten down the muffler screws
firmly.
– Reassemble all other parts in the
reverse sequence.
4.3 Oil Seals
The engine must be disassembled
to replace the oil seals.
– Remove the engine, b4.5
– Remove the engine pan, b4.6
– Pull the crankshaft upwards a
little but not out of the cylinder.
:Pull off the oil seals (1).
– Clean the sealing faces and
install new oil seals, b4.6
– Install the engine pan, b4.6
– Degrease the crankshaft taper,
b13
– Install the engine, b4.5
0002RA462 TG
11
4.4 Shroud
– Remove the starter cover, b6.2
:Take out the screws (arrows).
:Take out the screw (1).
:Lift the shroud (1) slightly and pull
it away.
0002RA169 TG0002RA170 TG
1
0002RA171 TG
1