Stihl FS 25-4 Bedienungsanleitung

1. Safety Precautions 1

2. Introduction 2

3. Specifications 3

3.1 Engine 3

3.2 Fuel System 3

3.3 Ignition System 4

3.4 Gearhead 4

3.5 Special Accessories 4

3.5.1 For User 4

3.6 Dimensions and

Wear Limits 5

3.7 Tightening Torques 6

4. Troubleshooting 7

5. Clutch 10

5.1 Removing and

Disassembling 10

5.2 Assembling and

Installing 10

6. Engine 11

6.1 Checking/Adjusting

Valve Clearance 11

6.2 Checking Oil Level/

Changing Oil 13

6.3 Exhaust Muffler 14

6.4 Rocker Arms/Pushrods 14

6.5 Cam Followers 15

6.6 Cam Gear 15

6.7 Diaphragm 15

6.8 Crankcase,

Lower Half 16

6.9 Crankshaft 17

6.10 Valves/Valve Springs 18

6.11 Crankcase/Cylinder 18

7. Ignition System 19

7.1 Ignition Module 19

7.1.1 Ignition Timing 20

7.1.2 Removing/Installing 20

7.2 Flywheel 21

8. Rewind Starter 22

8.1 General 22

8.2 Rope Rotor 22

8.3 Starter Rope 23

8.4 Starter Grip 23

8.5 Rewind Spring 24

8.5.1 Replacing 24

8.5.2 Tensioning 24

8.6 Starter Cup/Fanwheel 25

9. Throttle Control 26

9.1 Throttle Trigger/Interlock

Lever (Bike Handle) 26

9.2 Contact Springs/Detent

Spring in Control Handle

(Bike Handle) 27

9.3 Throttle Trigger/Interlock

Lever (Loop Handle) 27

9.4 Slide Control

(Loop Handle) 28

9.5 Throttle Cable 29

9.5.1 Replacing 29

9.5.2 Adjusting 30

10. AV System 30

11. Fuel System 32

11.1 Air Filter 32

11.2 Carburetor 32

11.2.1 Leakage Test 32

11.2.2 Removing/Installing 33

11.2.3 Adjusting Idle Speed 34

11.3 Tank Vent 35

11.4 Pickup Body 35

11.5 Fuel Hoses 36

11.6 Fuel Tank 37

12. Shaft 38

12.1 Bike Handle 38

12.2 Loop Handle 38

12.3 Drive Shaft/

Flexible Liner 39

12.4 Drive Tube 40

13. Cutting Tool Drive 41

13.1 Gearhead 41

13.2 Clutch Drum 41

14. Special Servicing

Tools and Aids 43

14.1 Special Servicing Tools 43

14.2 Servicing Aids 44

15. Maintenance chart 45

1. Safety

Precautions

If the brushcutter is started up

in the course of repairs or mainten-

ance work, observe all local and

country-specific safety regulations

as well as the safety precautions

and warnings in the owner’s

manual.

Gasoline is an extremely flamma-

ble fuel and can be explosive in

certain conditions.

Improper handling may result in

burns or other serious injuries.

Warning! Do not smoke or bring

any fire or flame near the fuel. All

work with fuel must be performed

outdoors only. Spilled fuel must be

wiped up immediately.

Wash hands thoroughly after

every contact with waste oil.

Do not pour waste oil down the

drain or allow it to soak into the

ground.

Collect waste oil and take it to an

official disposal site for environ-

ment-friendly disposal.

FS 25-4, 65-4

Contents

FS 25-4, 65-4 1

Thisservicemanualcontainsdetai-

leddescriptionsofalltherepair

andservicingproceduresspecific

tothispowertoolseries.

Thereareseparatehandbooksfor

servicingproceduresforstand-

ardizedpartsandassembliesthat

areinstalledinseveralSTIHLpo-

wertoolmodels.Referenceis

madetothesehandbooksinthe

appropriatechaptersinthis

manual.

Servicingthecarburetorisdescri-

bedintheseparate"Carburetors"

manual.

Asthedesignconceptofmodels

FS25-4andFS65-4isalmost

identical,thedescriptionsand

servicingproceduresinthis

manualgenerallyapplytoboth

machines.Differencesare

describedindetail.

Youshouldmakeuseofthe

illustratedpartslistswhilecarrying

outrepairwork.Theyshowthe

installedpositionsoftheindividual

componentsandassemblies.

Refertothelatesteditionofthe

relevantpartslisttocheckthepart

numbersofanyreplacementparts

needed.

PartslistsonmicroficheandCD-

ROMarealwaysmoreuptodate

thanprintedlists.

Afaultonthepowertoolmayhave

severalcauses.Apartfromthe

chapter"Troubleshooting"inthis

manual,alsoconsultthetroubles-

hootingchartsforallassembliesin

the"StandardRepairs,Troubles-

hooting"handbook.

Refertothe"TechnicalInforma-

tion"bulletinsforengineering

changeswhichhavebeenintro-

ducedsincepublicationofthis

servicemanual.Technicalinforma-

tionbulletinsalsosupplementthe

partslistuntilarevisededitionis

issued.

Thespecialservicingtoolsmen-

tionedinthedescriptionsare

listedinthelastchapterofthisma-

nual.

Usethepartnumberstoidentify

thetoolsinthe"STIHLSpecial

Tools"manual.

Themanuallistsallspecial

servicingtoolscurrentlyavailable

fromSTIHL.

Symbolsareincludedinthetext

andpicturesforgreaterclarity.

Themeaningsareasfollows:

Inthedescriptions:

•=Actiontobetakenas

shownintheillustration

(abovethetext)

-=Actiontobetakenthat

isnotshowninthe

illustration

(abovethetext)

Intheillustrations:

=Pointer

=Directionofmovement

Servicemanualsandalltechnical

informationbulletinsdescribing

engineeringchangesareintended

exclusivelyfortheuseofSTIHL

servicingdealers.Theymustnot

bepassedtothirdparties.

Servicingandrepairsaremade

considerablyeasierifthemachine

ismountedonassemblystand(2)

59108903100withtheaidof

clamp(1)59108908800.

Securetheclamptotheassembly

standwithtwowashersandtwo

M8nuts.

Thecompletemachinecanthen

beswivelledtothebestposition

fortheongoingrepairandthislea-

vesbothhandsfree.

AlwaysuseoriginalSTIHL

replacementparts.

Theycanbeidentifiedbythe

STIHLpartnumber,

the

STIHL

logo

andthe

STIHLpartssymbol

(

Thesymbolmayappearaloneon

smallparts.

2. Introduction

2FS25-4,65-4

3.1 Engine

Singlecylinderfour-strokeoverheadvalveengine

FS25-4 FS65-4

Type: GX22 GX31

Displacement: 22cm331cm3

Bore:33mm39mm

Stroke:26mm26mm

PoweroutputtoISO8893: 0.6kW(0.8bhp) 0.85kW(1.2bhp)

at7,000rpm at7,000rpm

Max.enginespeed: Maximumrpmisdeterminedbymainjetandisnotadjustable

Idlespeed: 3,100±200rpm

Compressionpressure: 29-59kPa(2.9-5.9bar)

at1,200rpm

Pistonpindiameter: 8mm

Rewindstarter: Pawlengagement

Pawls: Singlepawlsystem

Reservepullonroperotor: min.1/2turn

Starterropediameter: 3mm

Clutch: Centrifugalclutchwithpress-fittedlinings

Clutchengagesat: 4,200±200rpm

Valveclearance

Inlet: 0.12±0.02mm

Exhaust: 0.15±0.02mm

Oilcapacity: 0.1l(100cm3)

Oilgrade: SAE15W-40

3.2 FuelSystem

Carburetor: Diaphragmcarburetor

Carburetorleakagetest

atgaugepressure: 8kPa(0.8bar)

Functionoftankvent

atgaugepressure: ≤3kPa(0.3bar)

undervacuum: ≤0.5kPa(0.05bar)

Fueltankcapacity: 0.45l(450cm3)0.65l(650cm3)

Fuel: Regularbrandnamegasoline

Octanerating: min.90RON

Airfilter: Oilimpregnatedfoamfilter

3.Specifications

FS25-4,65-4 3

3.3 Ignition System Type: Electronic magneto

ignition (breakerless)

with integral trigger unit

Ignition timing: 27 degrees B.T.D.C.

Air gap: 0.35 - 0.5 mm

Spark plug (suppressed): NGK CR5HSB,

Denso U16FSR-UB

Electrode gap: 0.6 - 0.7 mm

3.4 Gearhead Type: Spiral-toothed

bevel gear drive

Gear ratio: 1:1.4

Bearings: Deep groove ball bearings

Lubrication: STIHL gear lubricant

0781 120 1117, 1118

(capacity 7 g)

3.5 Special Accessories

3.5.1 For User Full harness

Safety glasses

Transport guard for

Metal cutting tools 4119 717 3005

STIHL gear lubricant (80 g tube) 0781 120 1109

STIHL gear lubricant (80 g tube) 0781 120 1117

4FS 25-4, 65-4

Description Standard Wear limit

Cylinder inside diameter 33.00 mm * 33.10 mm *

39.00 mm ** 39.10 mm **

Piston outside diameter 32.99 mm * 32.90 mm *

38.99 mm ** 38.90 mm **

Piston pin outside diameter 8.00 mm 7.95 mm

Cam lift 22.79 mm 22.49 mm

(inlet and exhaust)

Free length of valve springs 23.40 mm 22.50 mm

Valve stem outside diameter

Inlet: 3.985 mm 3.900 mm

Exhaust: 3.950 mm 3.880 mm

Valve guide inside diameter 4.000 mm 4.060 mm

Clearance between valve stem and guide

Inlet: 0.015 - 0.048 mm 0.098 mm

Exhaust: 0.050 - 0.083 mm 0.120 mm

Valve head diameter

Inlet: 12.5 mm *

13.5mm**

Exhaust: 12.0 mm

Clutch lining: 2.0 mm 1.0 mm

* FS 25-4

** FS 65-4

3.6 Dimensions and Wear Limits

FS 25-4, 65-4 5

DG and P screws (Plastoform) are used in polymer and lightmetal 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 detrimentally affecting 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 For component Torque Remarks

size Nm

Pan head screw M5x12 Valve cover 4.0

Pan head screw M5x22 Valve cover 4.0

Nut M5 Valve adjusting screw 5.0

Collar nut M8 Flywheel 15.0

M8 Starter cup 8.0

Nut M5 Carburetor 5.0

Pan head screw M6x28 Clutch shoes 10.0 1)

Pan head screw M8x28 Clutch shoes 15.0 2)

Pan head screw M4x16 Cam gear cover 3.0

Pan head screw M5x18 Crankcase 5.0

Pan head screw M5x55 Crankcase cover

1st stage 3.0

2nd stage 7.0

Spline screw IS-DG5x24 Gear housing/drive tube 8.5

Spline screw IS-M5x12 Clamp, control handle/

drive tube (loop handle) 2.0

Spline screw IS-M5x16 AV sleeve/drive tube (clamp screw) 5.5

Spline screw IS-M5x12 Clamp, control handle/drive tube 2.0

Spline screw IS-M5x16 Clamp/drive tube (harness) 4.5

Spline screw IS-M5x30 Control handle (bike handle) 2.0

Spline screw IS-M6x25 Clamp/loop handle 4.5

Screw plug M11x10 Gearhead 8.5

Plastoform screw IS-P4x16 Control handle/handle moldings 1.0

Collar screw IS-P3.5x10.6 Detent spring/slide control

(bike handle) 1.1

Nut M12x1.5 L Cutting tool 25.0

Spline screw IS-M5x16 Deflector/gearhead 4.3

All other screws M3 1.0

and nuts M5 5.0

M6 9.0

Use the following procedure to fit a DG or P screw in an existing thread:

– Place the DG or P 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,

which would weaken the assembly.

1) FS 25-4

2) FS 65-4

Note: Power screwdriver speed settings for polymer: Plastoform screws max. 600 rpm

DG screws max. 500 rpm

3.7 Tightening Torques

6FS 25-4, 65-4

1. Engine difficult to start

Check fuel level in tank.

Adequate fuel in

tank

Operate manual fuel pump

and check that fuel is flowing to

carburetor.

Fuel flows to

carburetor

Remove spark plug and

check for damp or oily

electrodes.

Damp

Check spark plug

for spark.

Powerful spark

Check compression.

Adequate compression

Install spark plug and start

engine according to

instructions.

No fuel

Fuel does not flow

to carburetor

Dry

No spark or only a

weak spark

Compressioninorder

Compression too low

Fill up with fuel and try starting

again.

– Check fuel line and fuel

filter for blockages.

– Faulty carburetor diaphragm

or float needle valve,

replace carburetor

Replace carburetor

– Change spark plug and

repeat the spark test.

– Check ignition lead for

damaged insulation and

leakage current.

– Check ignition coil.

Check combustion chamber

for excessive build-up of

combustion deposits.

– Check, adjust valve

clearance.

– Valves must be in good

condition.

– Check piston, rings and

cylinder for wear.

4. Troubleshooting

FS 25-4, 65-4 7

2. Erratic running behavior at low rpm

Inspect air filter element.

Not dirty

Remove spark plug and

check electrodes for coking,

check electrode gap.

Normal

Check to see if fuel line is kin-

ked, pinched or cracked. Check

carburetor for looseness or air

entering through spacer flange.

Normal

Check fuel filter.

Not dirty

Check correct function of

carburetor.

Normal

Check compression.

Normal

Start engine according to

instructions.

Dirty

Abnormal

Dirty

Abnormal

Clean, replace air filter

element.

– Clean spark plug and

adjust electrode gap.

– Replace spark plug.

– If fuel line is kinked

or pinched, fit a

new one.

– Tighten loose carburetor

nuts. Examine spacer

flange for damage and

install properly.

Clean, replace filter.

Replace carburetor.

– Check, adjust valve

clearance.

– Check combustion chamber

for excessive build-up of

combustion deposits.

– Check valves for faults.

– Check piston, rings and

cylinder for wear.

8FS 25-4, 65-4

3. Erratic running behavior at high rpm

Inspect air filter element.

Not dirty

Remove spark plug and

check electrodes for coking,

check electrode gap.

Normal

Check to see if fuel line is kin-

ked, pinched or cracked. Check

carburetor for looseness or air

entering through spacer flange.

Normal

Check correct function of

carburetor.

Normal

Start engine according

to instructions.

Dirty

Abnormal

Clean, replace air filter

element.

– Clean spark plug and

adjust electrode gap.

– Replace spark plug.

– If fuel line is kinked

or pinched, fit a

new one.

– Tighten loose carburetor

nuts. Examine spacer

flange for damage and

install properly.

Replace carburetor.

FS 25-4, 65-4 9

Troubleshootingchart-see

"StandardRepairs,Trouble-

shooting"handbook.

-Removetheshroud-see6.1.

-Removecontrolhandlefrombike

handle-see12.1.

-Onloophandlemachine,dis-

connectthrottlecablefrom

carburetor-see9.5.1.

•Takeoutthescrews.

-Pulloffclutchhousingwithdrive

tube.

•Inspectclutchdrum.There

shouldbenoscoresorsigns

ofexcessivewear.

Important:Iftherearesignsof

seriouswearontheinside

diameter,fitanewclutchdrum-

see13.2.

-Blockpistonwithlockingscrew-

see7.2.

•Takeoutthecollarscrews(1).

•Removetheclutchshoes(2).

•Twisttheclutchshoesand

detachthespring.

Important:Clutchshoesmust

alwaysbereplacedinpairs.

•Attachspringtoclutchshoes.

•Fitthewashers.

•Fitclutchshoessothatthe

marksfaceoutwards.

""=FS25-4

"R"=FS65-4

5. Clutch

5.1 RemovingandDisassembling 5.2 AssemblingandInstalling

10 FS25-4,65-4

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