Stihl 4180 Series User manual

STIH)
STIHL Basismotor 4180 2007-11
HL 100
HT 100
HT 101
HT 130
HT 131
KM 90
KM 100
KM 110
KM 130
FC 90
FC 95
FC 100
FC 110
FS 90
FS 100
FS 110
FS 130

1Series 4180 Powerhead
q
© ANDREAS STIHL AG & Co. KG, 2007
Contents
1. Introduction 2
2. Safety Precautions 3
3. Specifications 4
3.1 Engine 4
3.2 Spark plug 4
3.3 Fuel System 4
3.4 Tightening Torques 5
4. Troubleshooting 7
4.1 Clutch 7
4.2 Rewind Starter 8
4.3 Ignition System 9
4.4 Carburetor 10
4.5 Engine 12
5. Rewind Starter/
Shroud 14
5.1 General 14
5.2 Removing and
Installing 14
5.3 Rope Rotor 14
5.4 Starter Rope 16
5.4.1 Tensioning 17
5.5 Pawl 18
5.6 Replacing the
Rewind Spring 18
5.7 Removing the Shroud 18
6. Fuel System 19
6.1 Air Filter 19
6.2 Carburetor 20
6.2.1 Leakage test 20
6.2.2 Removing
and Installing 21
6.2.3 Manual Fuel Pump 21
6.2.4 Metering Diaphragm 22
6.2.5 Inlet Needle 23
6.2.6 Fixed Jet 23
6.2.7 Pump Diaphragm 23
6.3 Accelerator Pump 25
6.4 Adjusting Idle Speed 25
6.4.1 Basic Setting 26
6.5 Tank Vent 27
6.5.1 Checking Operation 27
6.5.2 Replacing Tank Vent 28
6.6 Fuel Supply 29
6.6.1 Cleaning the
Fuel Tank 29
6.6.2 Fuel Hoses and
Pickup Body 29
6.6.3 Fuel Tank 31
7. Engine 31
7.1 Compression
Pressure 32
7.2 Checking / Adjusting
Valve Clearance 32
7.3 Rocker Arms/
Pushrods 34
7.4 Cam Followers,
Cam Gear 35
7.4.1 Decompression
System 36
7.5 Muffler / Spark
Arresting Screen 36
7.6 Clutch 37
7.6.1 Removing and
Disassembling 37
7.6.2 Assembling and
Installing 38
7.6.3 Clutch Drum and
Bearing 39
7.7 Flywheel 40
7.8 Crankshaft 41
7.8.1 Replacing
the Oil Seals 41
7.8.2 Crankcase,
Lower Half 43
7.8.3 Crankshaft 44
7.8.4 Piston 45
7.8.5 Piston Rings 47
7.9 Valves/Valve Springs 48
7.10 Upper Half of
Crankcase with
Cylinder 49
7.11 Leakage Test 49
8. Ignition System 51
8.1 Spark Plug Boot 51
8.2 Ignition Module 52
8.2.1 Ignition Timing 52
8.2.2 Removing and
Installing 52
8.3 Testing the Ignition
System 54
8.4 Ignition System
Troubleshooting 55
9. Throttle Control 58
9.1 Throttle Trigger,
Lockout Lever 58
9.2 Tensioner 59
9.3 Adjusting Throttle
Cable 59
9.3.1 Control Handle
with Slide 59
9.3.2 Control Handle
without Slide 60
9.3.3 Checking Adjustment 61
9.4 Slide Control 61
10. AV System 62
11. Special Servicing
Tools 63
12. Special Accessories 64

2Series 4180 Powerhead
This service manual contains
detaileddescriptionsofallthe repair
andservicingproceduresspecificto
this powerhead.
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 lists to check the part
numbers of any replacement parts.
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 last
chapter of this manual. Use the part
numbers to identify the tools in the
"STIHL Special Tools" manual.
Symbolsareincludedinthetextand
pictures for greater clarity.
The meanings are as follows:
In the descriptions:
:= Action to be taken that is
shown in the illustration
(above the text)
– = Action to be taken that is
not shown in the illustration
(above the text)
b4.2 = Reference to another
chapter, i.e. chapter 4.2 in this
example
+= Situation applies from
serial No.
*= Situation applies up to
serial No.
In the illustrations:
APointer (short arrow)
aDirection of movement
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.
Servicing and repairs are made
considerably easier if the
powerheadismountedonassembly
stand (2) 5910 890 3100 with the
aid of clamp (1) 5910 890 8800.
The powerhead can then be
swivelled to the best position for the
ongoing repair. This leaves both
VA
249RA!63
2
1
hands free.
Always use original STIHL
replacement parts.
They can be identified by the
STIHL part number,
the {logo and the
STIHL parts symbol (
This symbol may appear alone on
small parts.
1. Introduction

3Series 4180 Powerhead
If the power tool 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.
Gasolineisanextremely flammable
fuel and can be explosive in certain
conditions.
Improper handling may result in
burns or other serious injuries.
Always wear suitable protective
gloves for operations in which
components are heated for
assembly or disassembly.
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.
2. Safety Precautions

4Series 4180 Powerhead
3. Specifications
Remarks: 1) install at inlet side only 2) may be installed at inlet and
exhaust sides
FS 90
FC 90, 95
KM 90
FS 100, 110
FC 100, 110
HT 100, 101
HL 100
KM 100, 110
FS 130
HT 130
HT 131
KM 130
3.1 Engine STIHL single cylinder four-stroke engine with mixture lubrication
Displacement: 28.4 cm331.4 cm336.3 cm3
Bore: 38 mm 40 mm 43 mm
Stroke: 25 mm 25 mm 25 mm
Engine power to ISO 8893 0.95 kW
at 7,000 rpm 1.05 kW at 7,000 rpm 1.4 kW at 8,500 rpm
Max. permissible engine speed with cut-off
by ignition module: 10,500 ± 500 rpm 10,500 ± 500 rpm 10,500 ± 500 rpm
Idle speed 2,800 rpm 2,800 rpm 2,800 rpm
Clutch: Centrifugal clutch, two clutch shoes without linings
Clutch engages at: 3,700 rpm 3,700 rpm 3,700 rpm
Valve clearance
Inlet valve: 0.10 mm 0.10 mm 0.10 mm
Exhaust valve: 0.10 mm 0.10 mm 0.10 mm
Valve diameter: 13.5 mm 13.5 mm 15.5 mm
Marking: A 1) A 1) B or :1)
E 2) E 2) I 2)
3.2 Spark plug
Type: BOSCH USR 7AC BOSCH USR 7AC NGK CMR 6H
Electrode gap: 0.5 mm 0.5 mm 0.7 mm
Air gap between ignition module
and flywheel: 0.15 ... 0.30 mm 0.15 ... 0.30 mm 0.15 ... 0.30 mm
3.3 Fuel System
Crankcase leakage test
at gauge pressure: 0.5 bar 0.5 bar 0.5 bar
under vacuum: 0.5 bar 0.5 bar 0.5 bar
Carburetor leakage test
at gauge pressure: 0.8 bar 0.8 bar 0.8 bar
Operation of tank vent
at gauge pressure: 0.3 bar 0.3 bar 0.3 bar
Fuel: as specified in instruction manual

5Series 4180 Powerhead
3.4 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
Nm
Socket head screw IS-M6x25 Cover washer/clutch shoe/flywheel 12.0
Socket head screw IS-DG4x18 Cover/engine pan 4.5
Socket head screw IS-M5x30 Control handle/locknut with washer 2.0 1)
Socket head screw IS-P4x16 Control handle, inner/outer moldings 1.3 1)
Socket head screw IS-P4x16 Control handle, inner/outer moldings 1.3 2)
Socket head screw IS-M5x12 Clamp/control handle 5.0 2)
Socket head screw IS-DG4x18 Cover/cylinder 4.5
Socket head screw IS-M5x21 Filter cover/filter housing 3.5
Collar nut M5 Filter housing/carburetor 3.5
Socket head screw IS-D5x24 Gear housing/drive tube 8.0
Socket head screw IS-M4x9.5 Screen/muffler 2.0
Socket head screw IS-M5x24 Shroud/cylinder 6.0
Collar screw M5x16 Rocker lever collar screw/cylinder 9.0
Socket head screw IS-M6x30 Clamp/drive tube/handle support 8.0 1)
Socket head screw M6x30 Coupling sleeve wingscrew 6.0 3)
Socket head screw IS-M6x25 Coupling sleeve/nut, clamp 9.0 3)
Socket head screw IS-DG5x24 Engine pan/cylinder 9.0
Socket head screw IS-M6x25 Clamp/loop handle/nut 4.5 2)
Socket head screw IS-DG5x24 Fan housing/shroud/engine pan 6.0
Socket head screw IS-DG5x24 Fan housing/engine pan 6.0
Socket head screw P3.5x9 Detent spring/slide control 1.1 1)
Socket head screw IS-M5x23 Loop handle/clamp/drive tube 6.0 4)
Socket head screw IS-DG5x24 Muffler/crankshaft 9.0
Socket head screw IS-DG5x24 Muffler/cylinder 9.0
Socket head screw IS-M5x16 Cutting attachment deflector/gear housing 4.5
Nut M8x1 Flywheel/crankshaft 17.0 5)
Socket head screw IS-M6x14 Clamp/carrying ring 4.5
Socket head screw IS-M5x12 Clamp/drive tube, fan housing 6.0
Socket head screw IS-DG5x24 Starter cover/cover/engine pan 6.0

6Series 4180 Powerhead
Fastener Thread size For component Torque
Socket head screw IS-DG5x24 Starter cover/tank/engine pan 6.0
Nut M8x1 Starter cup/crankshaft 17.0
Socket head screw IS-M5x30 Valve cover/cylinder 3.5
Screw plug M11x10 Screw plug/gearbox 10.0
Spark plug IS-M10x1 Spark plug 9.0
Socket head screw IS-DG4x18 Ignition module/cylinder 4.5
Socket head screw IS-DG5x32 Spacer flange/cylinder 9.0
Socket head screw IS-P5x14 Fan housing/clutch drum bearing 4.0 6)
Remarks:
1) Version with bike handle
2) Version with loop handle
3) KombiEngine
4) FS 100 RX
5) Degrease crankshaft/flywheel and mount oil-free
6) FS 90, 100; KM 90, 100; FC 90, 95, 100
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.
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.
Coat micro-encapsulated screws with medium strength Loctite 243 before reinstalling.

7Series 4180 Powerhead
4. Troubleshooting
4.1 Clutch
Condition Cause Remedy
Attachment stops under load at full
throttle Clutch badly worn Install new clutch
Clutch drum badly worn Install new clutch drum
Attachment runs when engine is
idling Engine idle speed too high Readjust with idle speed screw (counterclockwise)
Clutch springs stretched or fatigued Install new clutch
Spring hooks broken Install new clutch

8Series 4180 Powerhead
4.2 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
Rewind spring broken (starter rope
does not rewind) Spring overtensioned – no reserve when rope is fully extended Fit new rewind spring
Very dirty or corroded Clean or replace rewind spring
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
Spring clip on pawl fatigued Fit new spring clip
Starter rope is difficult to pull or
rewinds very slowly Starter mechanism is very dirty (dusty conditions) Thoroughly clean complete starter mechanism
Lubricating oil on rewind spring
becomes viscous at very low
outside temperatures (spring
windings stick together)
Clean rewind spring with standard
cleaner, then pull rope carefully
several times until normal smooth
action is restored. Then coat with
resin-free oil.

9Series 4180 Powerhead
4.3 Ignition System
Warning:
Exercise extreme caution while
carryingoutmaintenanceandrepair
work on the ignition system. The
ignition system. The high voltages
which occur can cause serious or
fatal accidents.
Condition Cause Remedy
Engine does not run No spark Check operation of slide control
and ignition module; replace
damaged parts
Spark plug dirty or faulty Clean or replace spark plug
Faulty insulation or break in ignition
coil, ignition lead or short circuit
wire
Use ohmmeter to check ignition coil
and lead for break. If break is
detected or resistance is high, fit a
new ignition coil and ignition lead;
check short circuit wire for ground
contact in run position
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 Install new spark plug
Weak spark or no spark Faulty insulation on ignition lead or
short circuit wire. Use ohmmeter to
check ignition lead for break. If
break is detected or resistance is
high, fit a new ignition lead.
Wrong air gap between ignition coil
and flywheel Reset air gap
Flywheel cracked or damaged Install new flywheel
Spark plug dirty or faulty. Check
slide control, ignition coil/lead for
damaged insulation and leakage
current.
Clean or replace spark plug.
Replace damaged parts of ignition
system

10 Series 4180 Powerhead
4.4 Carburetor
Condition Cause Remedy
Carburetor floods; engine stalls Inlet needle not sealing. Foreign
matter in valve seat or cone
damaged
Remove and clean or replace inlet
needle, clean fuel tank, pickup
body and fuel hose if necessary
Inlet control lever sticking on
spindle Free off inlet control lever
Helical spring not located on nipple
of inlet control lever Remove the inlet control lever and refit it correctly
Perforated disc on diaphragm is
deformed and presses constantly
against the inlet control lever
Fit new metering diaphragm
Inlet control lever too high (relative
to design position) Set inlet control lever flush with upper face of housing or bottom of
metering chamber
After more than five starting
attempts with choke shutter closed Open choke shutter after no more than five starting attempts
Poor acceleration Idle jet too lean Back off low speed screw slightly
Main jet too lean Back off high speed screw slightly
Inlet control lever too low (relative
to design position) Set inlet control lever flush with upper face of housing or bottom of
metering chamber
Inlet needle sticking to valve seat Remove inlet needle and clean
valve seat
Connecting bore to atmosphere
blocked Clean bore
Diaphragm gasket leaking Fit new diaphragm gasket
Metering diaphragm damaged or
shrunk Fit new metering diaphragm

11Series 4180 Powerhead
Condition Cause Remedy
Engine will not idle,
idle speed too high Throttle shutter opened too wide by idle speed screw Reset idle speed screw
Intake stub leaking Seal or replace intake stub
Engine stops while idling Idle jet bores or
ports blocked Clean jet bores and ports and blow clear with compressed air
Idle jet too rich Screw down low speed screw (L)
slightly
Setting of idle speed screw
incorrect – throttle shutter
completely closed
Set idle speed screw (LA) correctly
Engine speed drops quickly under
load – low power Air filter dirty Clean the air filter
Tank vent faulty Clean the tank vent, replace if
necessary
Leak in fuel hose between tank to
fuel pump Seal connections or install new fuel hose
Pump diaphragm damaged or
fatigued Fit new pump diaphragm
Main jet bores or ports blocked Clean bores and ports
Fuel pickup body dirty Fit new pickup body
Fuel strainers dirty Clean fuel strainers

12 Series 4180 Powerhead
4.5 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
Check compression Check combustion chamber for
excessive build-up of combustion
deposits,
check condition of valves and valve
clearances
Gasket on carburetor spacer flange
leaking Install new gasket
Decompression lever sticking Install new cam gear
Muffler carbonized Clean muffler, or replace if
necessary
Crankcase damaged (cracks) Replace the crankcase
Engine does not deliver full power
or runs erratically Secondary air seepage through faulty gaskets on spacer flange Install new gaskets
Piston rings worn or broken Install new piston rings
Muffler / spark arresting screen
carbonized Clean muffler (inlet and exhaust openings), replace spark arresting
screen (if fitted)
Air filter element dirty Fit new air filter element
Fuel/impulse hose severely kinked
or damaged Fit new hoses or position them free from kinks
Pump diaphragm torn Install new pump diaphragm
Decompression lever sticking Install new cam gear

13Series 4180 Powerhead
Condition Cause Remedy
Engine overheating Insufficient cylinder cooling. Air
inlets in fan housing blocked or
cooling fins on cylinder very dirty
Thoroughly clean all cooling air
openings and the cylinder fins

14 Series 4180 Powerhead
If the action of the starter rope
becomes very stiff and the rope
rewinds very slowly or not
completely, it can be assumed that
the starter mechanism is in order
but plugged with dirt. At very low
outsidetemperaturesthelubricating
oil on the rewind spring may thicken
and cause the spring windings to
stick together. This has a
detrimental effect on the function of
the starter mechanism. In such a
case it is sufficient to clean the
rewind spring with a standard
commercial cleaner and then coat it
with STIHL special lubricant.
Carefully pull out the starter rope
several times and allow it to rewind
until its normal smooth action is
restored.
:Remove the screws (arrows)
from the rewind starter.
– Lift away the rewind starter.
Reassemble in the reverse
sequence.
VA
249RA001
– Tighten down the screws, b3.4
– Remove the rewind starter,
b5.2
Relieving tension of rewind
spring:
The spring will not be under tension
if the starter rope is broken.
– Pull out the starter rope about
20 cm and hold the rope rotor
steady.
– Engage the rope in the notch on
the rotor, and make a loop.
– Use the starter rope to turn the
rotor clockwise until tension is
relieved.
VA
249RA154
5. Rewind Starter/Shroud
5.1 General 5.2 Removing and Installing 5.3 Rope Rotor

15Series 4180 Powerhead
:To remove the rope rotor, ease
the spring clip (1) out of the
groove in the starter post.
:Remove the washer (2) and pawl
(3).
VA
249RA025
3
12
:Carefullypull theroperotor(1)off
the starter post.
– To replacetheroperotor,remove
the starter rope, b5.4
1
VA
249RA026
Installing:
Coat bore in rope rotor with STIHL
special lubricant, b12.
:Fit the rope rotor on the starter
post so that the driver (1) on the
rotor slips behind in the inner
VA
249RA141
1
2
spring loop (2).
Turn the rope rotor a little and let it
go. It must spring back.
– Fit the pawl and washer. Engage
spring clip in the groove on the
starter post.
The spring clip (1) must engage the
guide peg (2) on the pawl and point
it counterclockwise.
VA
249RA027
2
1
Handle the spring clip with care.
The rewind starter may not function
properly if the spring clip is bent.
– Install the starter rope, b5.4
– Tension the rewind spring,
b5.4.1

16 Series 4180 Powerhead
– Remove the rewind starter,
b5.2
– Remove remaining rope from the
rope rotor and starter grip.
:Thread end of new rope through
the underside of the starter grip
and pull it out.
:Secure the end of the rope with
one of special knots shown.
– Pull the rope back into the starter
grip.
VA
982RA036
– Thread the other end of the rope
through the guide bush (2) from
outside.
– Thread the rope through the hole
in the side of the rope rotor (1).
:Pull out the rope and secure it
VA
249RA028
1
2
with a simple overhand knot.
:Pull the rope back into the rotor
so that the knot locates in the
recess (1).
– Tension the rewind spring,
b5.4.1
1
VA
249RA029
5.4 Starter Rope

17Series 4180 Powerhead
– Remove the rewind starter,
b5.2
:Make a loop in the starter rope.
VA
249RA153
:Engage the rope in the notch on
the rotor. Grip the rope close to
the rotor and use it to turn the
rope rotor six full turns clockwise.
VA
249RA154
:Hold the rope rotor steady.
:Pull out the twisted rope with the
starter grip and straighten it out.
– Hold the starter grip firmly to keep
the rope tensioned.
VA
249RA155
– Let go of the rope rotor and
slowly release the starter grip so
that the rope winds itself onto the
rotor.
The rewind spring is correctly
tensioned when the starter grip sits
firmly in the rope guide bushing
without drooping to one side. If this
is not the case, tension the spring
by one additional turn.
When the starter rope is fully
VA
249RA156
extended, it must still be possible to
rotate the rope rotor at least another
half turn before maximum spring
tension is reached. If this is not the
case, pull the rope out, hold the
rope rotor steady and take off one
turn of the rope.
– Install the rewind starter,
b5.2
5.4.1 Tensioning

18 Series 4180 Powerhead
:Ease the spring clip (1) off the
starter post.
Do not take the rope rotor off the
starter post.
:Pull the pawl (2) out of the rope
rotor.
VA
249RA031
1
2
– Lubricate peg on pawl with
grease, b12
– Remove the rope rotor, b5.3
The pieces of broken spring may
still be under tension and may fly
apart unexpectedly when you
remove them.
To reduce the risk of injury,
wear a face shield and work gloves.
– Remove the spring housing and
parts of the spring.
– Lubricate the new spring with a
few drops of resin-free oil.
:Position the new spring housing
(bottom plate must face up) as
shown (arrows) and push it
home.
– Install the rope rotor, b5.3.
– Install the starter rope, b5.4
VA
249RA143
Reassemble all other parts in the
reverse sequence.
– Remove the rewind starter,
b5.2
:Take out the screws (1 and 2).
:Carefully pull off spark plug boot
(3) vertically.
VA
249RA004
3
1
2
:Take out the screw (1).
– Remove the shroud upwards,
and pull the spark plug boot
through the shroud at the same
time.
Reassemble in the reverse
1
VA
249RA003
sequence.
– Tighten down the screws, b3.4
5.5 Pawl 5.6 Replacing the Rewind
Spring 5.7 Removing the Shroud

19Series 4180 Powerhead
Dirty air filters reduce engine power,
increase fuel consumption and
make starting more difficult.
The air filter must be cleaned when
there is a noticeable loss of engine
power.
– Close the choke shutter.
– Clean away any loose dirt from
around the filter and filter cover.
:Loosen the slotted screw (1) and
lift away the filter cover.
249RA005
1
VA
:Remove the filter (1).
The filter element is not washable. If
it is heavily loaded with dirt, fit a new
one.
249RA006
1
VA
:Take out the screws (1 and 2).
– Remove the air filter housing.
VA
249RA007
21
:Remove the paper gasket (1) and
fit a new one.
When reassembling, check that the
air filter housing is of the right type:
VA
249RA008
1
:Air filter housing (A) without stub
for tank vent without return line,
b6.5
:Air filter housing (B) with stub
(arrow) for tank vent with return
line to clean air side, b6.5
249RA183 BL
AB
Install air filter housing (B) with stub
only with the connecting hose to the
tank vent.
Unfiltered air would be sucked in if
the connecting hose is not fitted.
This would result in an increased
rate of wear and a risk of engine
damage.
Reassemble all other parts in the
reverse sequence.
– Tighten down screws on air filter
housing, b3.4
– Tighten down screw air on filter
cover, b3.4
6. Fuel System
6.1 Air Filter