1. Introduction 2
2. Specifications 3
2.1 Engine 3
2.2 Fuelsystem 3
2.3 Ignitionsystem 4
2.4 Gearbox 4
2.5 Cuttingattachment 5
2.6 Specialaccessories 6
2.6.1 Fortheuser 6
2.6.2 Forservice 6
2.7 Tighteningtorques 7
3. Clutch 9
3.1 Disassembly 9
3.2 Assembly 10
4. Engine 11
4.1 Muffler/sparkarresting
screen 11
4.2 Leakagetesting 11
4.2.1 Preparations 12
4.2.2 Pressuretest 12
4.2.3 Vacuumtest 13
4.3 Oilseals 14
4.4 Exposingthecylinder/
spacerflange 15
4.5 Cylinderandpiston 16
4.5.1 Removal 16
4.5.2 Installation 16
4.6 Pistonrings 18
4.7 Crankcase 18
4.7.1 Removingthecrank-
shaft 18
4.7.2 Installingthecrankshaft20
5. Ignitionsystem 23
5.1 Sparkplugterminal 23
5.2 Ignitionmodule 24
5.2.1 Ignitiontiming 24
5.2.2 Removalandinstalla-
tion 25
5.3 Flywheel 26
6. Rewindstarter 27
6.1 General 27
6.2 Startercover 27
6.3 Rewindspring 28
6.3.1 Replacement 28
6.3.2 Tensioning 28
6.4 Starterrope
(ElastoStart) 29
6.5 Startergrip
(ElastoStart) 30
6.6 Startercarrier/pawl 30
7. Throttlecontrol 31
7.1 Throttletrigger/interlock
lever(throttlecablewith
oneshort-circuitwire) 31
7.2 Throttlecablewithone
short-circuitwire 32
7.3 Contactspring/detent
springincontrolhandle
(throttlecablewithone
short-circuitwire) 33
7.4 Throttletrigger/interlock
lever(throttlecablewith
twoshort-circuitwires)33
7.5 Throttlecablewithtwo
short-circuitwires 34
7.6 Adjustingthethrottle
cable 34
8. Fuelsystem 35
8.1 Airfilter 35
8.2 Carburetor 35
8.2.1 Leakagetesting 35
8.2.2 Removaland
installation 36
8.2.3 Adjustment
(twoadjustingscrews)37
8.2.4 Adjustment
(oneadjustingscrew) 38
8.3 Tankvent 39
8.4 Pickupbody 39
8.5 Fueltank/hoses 40
9. AVsystem 41
9.1 Repair 41
10. Shaft 43
10.1 Cowhornhandle 43
10.2 Loopedhandle 43
10.3 Driveshaft/insulating
tube 45
10.4 Protectivetube 46
11. Cuttingtooldrive 47
11.1 Bearinghousing
(FS75) 47
11.2 Gearbox(FS80,85) 47
11.3 Gearbox(FC75) 48
11.4 Clutchdrum 50
12. Cuttingdevice(HL75)51
12.1 Gearbox 51
12.2 Cuttingblade 51
12.3 Gearwheel 53
13. Specialservicetools
andaids 55
13.1 Specialtools 55
13.2 Servicingaids 57
©1996,AndreasStihlAG&Co.,Waiblingen
FS75
Contents
1
ThisRepairManualcontainsa
detaileddescriptionofallthetypi-
calrepairworkrequiredforthese
seriesofpowertools.
Repairstobeundertakenonstan-
dardpartsandassemblieswhich
areusedinseveralSTIHLpower
toolseriesaredescribedinsepa-
raterepairmanuals.
Attentionisdrawntotheseinstruc-
tionsattherelevantpointsinthis
manual.
SincethebrushcuttersFS75,
FS80,FS85,FC75andthe
hedgetrimmerHL75arealmost
identical,thedescriptionsandser-
vicingproceduresinthismanual
generallyapplytoallfivemodels.
Differencesaredescribedindetail.
Theillustratedsparepartslists
shouldalsobeconsultedwhencar-
ryingoutrepairs,fortheyshowthe
installedpositionandsequenceof
assemblyfortheindividualparts.
Thelatesteditionoftherespective
partslistsshouldalwaysbeused
whendeterminingthepartnum-
bersoftherequiredreplacement
parts.Microfilmsaremoreup-to-
datethanprintedsparepartslists!
Faultsinthemachinemaybedue
toseveralcauses.
Notethe"Summaryoffaults"for
allfunctiongroupsinthemanual
"Troubleshooting,standard
repairs".
Notethe"TechnicalInformation"
sheets,fortheydescribetechnical
changesimplementedafterpubli-
cationofthisRepairManual.The
TechnicalInformationsheetssupp-
lementthepartslistuntilanewedi-
tionispublished.
Thespecialtoolsmentionedinthe
textarelistedinthelastchapterof
thismanual.Thetoolscanalso
beidentifiedinthemanualof
"STIHLtools"onthebasisoftheir
partnumber.
Themanuallistsallthetoolssupp-
liedbySTIHL.
Thefollowinggraphicsymbolsare
usedinthetextandillustrationsin
ordertomakethismanualeasier
touseandunderstand:
Inthetext:
•
=Activitytobecarriedout;
correspondstotheactivityin
thepictureabovethetext.
-=Activitytobecarriedout,butis
notshowninthepictureabove
thetext.
Intheillustrations:
- =Shortarrowindicating:Note
- =Longarrowindicating:Goto
RepairManualsandTechnicalIn-
formationsheetsshouldalwaysbe
onhandwhereverrepairsarecar-
riedout.Theymustnotbepassed
ontothirdparties.
Repairscanbecarriedoutmore
easilybymountingthepowerunit
ontheassemblystand(2)
59108903100withtheclamping
plate(1)59108902100.
Thepowerunitcanthenbeswivel-
ledintothemostsuitableworking
position,leavingbothhandsfree
fortheworkitself.
SecuredwithM5x30screwsafter
disassemblingtheprotectivetube,
shroud,startercoverandremo-
vingthefueltank.
AlwaysuseoriginalSTIHLreplace-
mentparts.
OriginalSTIHLpartscanbeiden-
tifiedbytheSTIHLpartnumber,
the logoandtheSTIHL
partssymbol .
Thesymbolmayappearaloneon
smallparts.
1. Introduction
11
22
392RA001 VA
2
2.1 Engine STIHLsingle-cylindertwo-strokeenginewithspecialimpregnatedcylinder
bore
Displacement: 25.4ccm
Bore: 34mm
Pistonstroke: 28mm
PoweroutputtoISO8893: 0.9kW(1.2HP)at8000rpm
Max.permissibleenginespeed
withoutcuttingblades(cut-offspeed):10500rpm(
+000rpm)
Max.speedoftheoutputshaft
(nominalvalue,gearhead): 8500rpm(FS75,FC75)
7500rpm(FS80,85)
Idlespeed: 2800rpm
Bearings: Heavy-dutydeepgrooveball
bearingsforcrankshaft;needle
cagesonsmallandbigends
Bigenddiameter: 8mm
Conrodlength: 52.5mm
Rewindstarter: ElastoStart
Pawls: Singlepawlsystem
Reservepullonroperotor: Atleastturn
Starterrope: Dia.3.0mm,800mmlong
Clutch: Centrifugalclutchwithoutlinings
Diameter: 66.5mm
Clutchengagesat: 3700rpm
Crankcaseleakagetest
atgaugepressure: 0.5bar
undervacuum: 0.5bar
2.2 Fuelsystem Carburetor: Diaphragmcarburetorwithoneor
twoadjustingscrews
Standardsettingforcarburetors
withtwoadjustingscrews
HighspeedadjustingscrewH: Backoffapprox.1turn
LowspeedadjustingscrewL: Backoffapprox.1turn
(standardsetting)
Carburetorleakagetestatgauge
pressure: 0.8bar
Functionoftankvent
atgaugepressure: 0.5bar
undervacuum: 0.1bar
Fueltankcapacity: 0.44l(440ccm)
Octanenumber: Atleast90RON
Fuelmixture: Regularbrandnamepetrol
Brandnametwo-strokeengineoil
Mixratio: 1:50whenusingSTIHL1:50
two-strokeengineoil
1:25whenusingallotherbrand-
nametwo-strokeengineoils
Airfilter: Foamandfeltelements
2. Specifications
3
2.3 Ignition system Type: Transistorized (breakerless)
magneto ignition with integrated
ballast
Air gap: 0.2 ... 0.5 mm
Ignition timing: 1.55 ... 2.25 mm before TDC at
n = 8000 rpm
Spark plug (suppressed): Bosch WSR 6F, NGK BPMR 7 A or
Champion RCJ 6Y
Electrode gap: 0.5 mm
Spark plug thread: M14 x 1.25
Length of thread: 9.5 mm
2.4 Gearbox * Type: Helical-toothed bevel gears
Gear ratio: 1.4 **
1.24 ***
Bearing: Deep groove ball bearing
Lubrication: STIHL gear lubricant
* FS 75 only has a bearing housing
** FS 80, 85
*** FC 75
4
2.5 Cutting attachment *
FS 75 FS 80 FS 85 FC 75
STIHL "Supercut 10-1"
mowing head
STIHL "Supercut 20-2" STIHL "Supercut 20-2"
mowing head mowing head
STIHL "Autocut 11-2"
mowing head
STIHL "Autocut 21-2" STIHL "Autocut 30-2"
mowing head mowing head
STIHL "Autocut 30-2" STIHL "Polymatic 30-2"
mowing head mowing head
STIHL "Polymatic 30-2" STIHL "Polymatic 30-2"
mowing head mowing head
STIHL "Polycut 10-3"
mowing head
STIHL "Polycut 20-3" STIHL "Polycut 20-3"
mowing head mowing head
Grass cutting blade Grass cutting blade
230-4 ** 230-4 **
Grass cutting blade Grass cutting blade
230-8 ** 230-8 **
Brush knife 250-3 **
Circular saw blade 200 ***
(scratcher-tooth)
Circular saw blade 200 ***
(chisel-tooth)
Blade
* Some cutting attachments may not be available in some countries on account of the different conditions
prevailing in each country.
** Only approved for brushcutters with cowhorn handle or looped handle with U-bar, together with the
guard 4119 713 4500.
*** Only approved for brushcutters with cowhorn handle.
5
2.6 Specialaccessories
2.6.1 Fortheuser Safetyharness
Safetygoggles
Barscabbardformetalcuttingtools
STIHLmulti-purposegrease(80gtube) 07811201109
STIHLgearlubricant(80gtube) 07811201117
2.6.2 Forservice Carburetorpartskit
forWalbrocarburetorWT447 41330071060
Carburetorpartskit
forZamacarburetorC1Q-S28A 42270071060
Gasketpanel(DINA3) 04572814003
6
2.7 Tighteningtorques
DGandP-type(Plastoform)screwsareusedinthermoplasticandalloyedmaterials.Thesescrewscutathread
inthematerialwhentheyarescrewedinforthefirsttime.Thematerialispermanentlydeformed.Thescrews
canberemovedandrefittedasoftenasdesired.Thestrengthofthescrewconnectionisnotimpairedifthespe-
cifiedtighteningtorqueismaintained.
Itisthereforeessentialtouseatorquewrench.
Fastener Thread Forcomponent Tighteningtorque Remarks
size (Nm)
Splinescrew IS-M5x25 Crankcase 9.5
Splinescrew IS-M5x25 Spacerflange/cylinder 5.5 1)
Splinescrew IS-DG5x24 Cylinder/crankcase 9.5
Splinescrew IS-M5x16 Muffler/cylinder 9.5
Splinescrew IS-M5x16 Muffler/crankcase 9.5
Splinescrew IS-M5x16 Tensioner/spacerflange 3.5
Splinescrew IS-M5x16 Fanhousing/crankcase 5.5
Splinescrew IS-M5x16 Starter/crankcase 5.5
Splinescrew IS-M4x20 Ignitionmodule/cylinder 4.5
Splinescrew IS-M5x16 Shroud/fanhousing 3.5
Splinescrew IS-M5x16 Shroud/startercover 3.5
M8 Clutch 21.0
M8 Startercarrier 20.0
M14x1.25 Sparkplug 20.0
Plastoformscrew IS-P5.5x12 Roperotorinstartercover 3.5
Splinescrew IS-M5x16 AVsleeve(clampingscrew) 5.5
Splinescrew IS-DG5x12 AVsleeve/protectivetube 2.5
Nut M5 Filterhousing/carburetor 4.0
Splinescrew IS-M5x18 Clampingcollar/bearinghousing 6.5 2)
Self-tappingscrew IS-B3.5x9.5 Bearinghousing/protectivetube 3.0 2)
Splinescrew IS-M5x33 Clampingcollar/guard 4.5 2)
Studbolt Detentspring/slidecontrol 1.0
Splinescrew IS-M5x16 Controlhandle,clampingcollar/
protectivetube(loopedhandle) 3.5 2)
Splinescrew IS-M6x50 Loopedhandle/protectivetube 3.5 2)4)
Splinescrew IS-DG5x16 Loopedhandle/handlehose 2.5 2)4)
Splinescrew IS-M6x25 Bracket,loopedhandle/protectivetube 4.5 3)
Splinescrew IS-M4x19 Controlhandle/handlemouldings
(loopedhandle) 1.0
Splinescrew IS-M5x16 Controlhandle,clampingcollars/
protectivetube 3.5
Plastoformscrew IS-P6x14 Linelimiterblade/guard 2.5 2)
Splinescrew IS-DG5x24 Gearhousing/protectivetube 9.0 3)
Splinescrew IS-M6x20 Gearhousing/protectivetube 7.5 4)
Screwplug M11x10 Gearbox 10.0
7
Fastener Thread Forcomponent Tighteningtorque Remarks
size (Nm)
Splinescrew IS-M5x18 Deflectorshield 4.3 3)
Locknut M10x1L Cuttingtool 25.0 3)
Plastoformscrew IS-P4x16 Controlhandle/handlemouldings
(cowhorn) 1.03)
Splinescrew IS-M5x30 Controlhandle(cowhorn) 2.0 3)
Splinescrew IS-M6x35 Clamp,tensioner/
protectivetube 4.5 3)
Splinescrew IS-DG5x12 Clamp/guard 5.5 4)
Splinescrew IS-DG5x12 Apron/guard 5.5 1)4)
Splinescrew IS-DG6x25 Guard/gearhousing/
tensioner 7.5 4)
Locknut M8x1.25L Blade 25.0 4)
Bearingbolt IS-M10x63 Wheel/guard 19.0 1)4)
Nuts,bolts M4 Allothers 2.5
Nuts,bolts M5 Allothers 4.5
Splinescrew IS-M4x16 Gearboxcover/gearhousing 3.5 5)
Splinescrew IS-M5x20 Bladeguide/gearhousing 9.5 5)
Splinescrew IS-M5x20 Gearbox/gearhousing 9.5 5)
Nut M5 Blade 9.5 5)
Screwplug M11x10 Gearboxcover 5.5 5)
WheninsertingtheDGandP-typescrewsinanexistingthread:
–InserttheDGorP-typescrewintheholeandturnitanticlockwiseuntilitgentlydropsintotheholeinaxial
direction.
–Turnscrewinclockwiseandtightenwiththespecifiedtorque,
Thisensuresthatthescrewengagestheexistingthreadanddoesnotcutanewthread,thuspreservingthe
strengthofthescrewconnection,
1)Withwasher
2)FS75
3)FS80,85
4)FC75
5)HL75
Note:Screwdriverspeedwhenworkinginplastic:Plastoformscrewsmax.600rpm,
DGscrews max.500rpm.
8
Refertomanual"Troubleshooting,
standardrepairs"fortroubleshoo-
tingprocedures..
•
Removescrewonstartercover.
•
Removescrew(1)onfan
housing.
-Liftoffshroud(2).
•
Removescrews.
-Pullofffanhousingwithprotec-
tivetubeandsetitaside.
•
Examineclutchdrum:itmustnot
bescoredorshowsignsofex-
cessivewear.
Important!Theremainingwall
thicknessmustbemeasuredifthe
insidediameterisdistinctlyworn.
Anewclutchdrummustbefitted-
see11.4-ifthewallthicknesshas
declinedtolessthan80%ofthe
originalvalue.
•
Disconnectsparkplugterminal
(1).
•
Removesparkplug(2).
•
Insertthelockingstrip(1)
00008935903inthecylinder.
3. Clutch
3.1 Disassembly
1122
392RA003 VA
392RA006 VA
11
392RA008 VA
392RA004 VA
80%
100%
145RA006
!
VA
11
22
392RA007 VA
392RA002 VA
9
•
Unscrew clutch from crankshaft
stub, turning it in the direction of
the arrow.
- Disassemble and reassemble
clutch, see manual "Trouble-
shooting, standard repairs".
•
Screw clutch onto crankshaft
with the smaller hexagon facing
outwards and torque down to
21 Nm.
•
Ensure that inlays are present in
fan housing; insert them if
necessary.
•
Position motor on fan housing,
ensuring that stubs (1) engage in
inlays (2).
- Insert screws in fan housing and
torque down to 5.5 Nm.
- Remove locking strip from
cylinder.
- Screw in spark plug and torque
downto20Nm.
Important! Check that the separa-
te connecting nut is securely loca-
ted on the screw thread of spark
plugs with separate nut and
tighten the nut if necessary.
- Reconnect spark plug terminal to
spark plug.
- Fit shroud.
392RA010 VA
392RA009 VA
392RA011 VA
11
11
22
22
392RA012 VA
3.2 Installation
10
Seemanual"Troubleshooting,
standardrepairs"fortrouble-
shootingprocedures.
Sparkarresterscreen
•
Removescrew(1).
•
Pulloutsparkarresterscreen(2).
-Cleansparkarresterscreen,fit
newscreenifnecessary.
Muffler
-Removeshroud,see3.1.
•
Removeouterscrew.
•
Removeinnerscrews.
-Liftoffmuffler.
•
Raisetongue(1)onretainer.
•
Pulloutseal(2).
Thepartsareinstalledinreverse
order.
-Presstonguedownagainafter
insertingseal.
-Tightenmufflerscrewstoa
torqueof9.5Nm.
-Refitshroud.
Defectiveoilsealsandgasketsor
cracksincastingscauseleaks.
Suchfaultsallowsupplementary
airtoentertheengineandthus
impairthefuel-airmixture.
Thismakesadjustmentofthe
specifiedidlespeeddifficult,ifnot
impossible.
Italsopreventsasmoothtransi-
tionfromidlespeedtopartorfull
throttle.
Thecrankcasecanbethoroughly
checkedforleakswiththecarbure-
torandcrankcasetesterandthe
vacuumpump.
11
22
392RA013 VA
392RA015 VA
11
22
392RA016 VA
4. Engine
4.1 Muffler/sparkarresterscreen 4.2 Leakagetesting
392RA014 VA
11
-Removecarburetor,see8.2.2.
•
Fitgasketinfrontofspacer
flange.
-Setpistontotopdeadcentre
(TDC)(canbeseenthroughthe
inletport).
-Checkthatsparkplugisseated
securely.
•
Fittestflange(1)11288504200.
•
Fitandtightennuts(2).
-Removeouterscrewonmuffler.
-Backoffinnerscrewshalf-way.
•
Slidesealingplate(1)
00008558106betweengasket
andcylinderexhaustportand
lightlyretighteninnerscrews.
Note:Thesealingplatemustfill
thespacebetweenthemounting
screwscompletely.
-Carryoutpreparatorysteps,
see4.2.1.
•
Slidepressurehoseoftester
11068502905overnippleon
testflange.
•
Closeventscrew(1)onrubber
bulb.
-Pumpairintocrankcasewith
rubberbulbuntilpressuregauge
indicatesapressureof0.5bar.
Thecrankcaseisairtightifthis
pressureremainsconstantforat
least20seconds.
4.2.1 Preparations 4.2.2 Pressuretest
392RA017 VA
11
392RA019 VA
11
22
392RA018 VA
392RA020 VA
143RA046 VA
1
12
•
Ifthepressuredrops,theleak
mustbelocatedandthefaulty
partreplaced.
Note:Tolocatetheleak,coatthe
suspectareawithoilandpressuri-
zethecrankcaseagain.Bubbles
willappearattheoil-coatedareaif
aleakexists.
-Thencarryoutvacuumtest,
see4.2.3.
-Openventscrewanddisconnect
hosewhentestiscomplete.
-Removetestflange.
-Loosenthemufflerscrews.
-Drawoutthesealingplateand
tightenthemufflerscrewswith
9.5Nm.
-Fitouterscrewofmufflerand
tightenwith9.5Nm.
-Installcarburetor,see8.2.2.
Oilsealstendtofailwhensub-
jectedtoavacuum,i.e.thesealing
lipliftsawayfromthecrankshaft
duringthepiston’sinductionstroke
becausethereisnointernalcoun-
terpressure.
Faultsofthiskindcanbedetected
withtheaidofavacuumpump.
Thepreparationsarethesameas
forthepressuretest,see4.2.2.
•
Connectsuctionhoseofvacuum
pump00008503501tonippleof
testflange.
•
Closeventscrew(1)onpump
cylinder.
•
Actuatelever(2)untilpressure
gauge(3)indicatesavacuumof
0.5bar.
Note:Theoilsealsareingood
conditioniftheindicatedvacuum
ismaintainedorifthepressure
risestonomorethan0.3bar
within20seconds.
Theoilsealsmustbereplacedif
thepressureinthecrankcasecon-
tinuestorise.
-Openventscrewanddisconnect
hosewhentestiscomplete.
-Removetestflange.
-Loosenmufflerscrews.
-Removesealingplateand
tightenscrewstoatorqueof9.5
Nm.
-Fitouterscrewinmufflerand
tightentoatorqueof9.5Nm.
-Installcarburetor,see8.2.2.
392RA021 VA
392RA020 VA
33
11
22
392RA022 VA
4.2.3 Vacuumtest
13
Itisnotnecessarytodisassemble
thecompleteengineifonlytheoil
sealshavetobereplaced.
Clutchside:
-Removeflywheel,see5.3.
-Lightlytaptheoilsealwitha
suitabletubeorpunchtoknock
itoutofitsseat.
•
Fitpuller(1)59108904400
(jaws00008933706withprofile
No.3.1).
-Tensionlegs.
-Pulloutoilseal.
Important!Thecrankshaftstub
mustnotbedamaged.
-Cleanthesealingareawithcom-
merciallyavailablesolvent-based
degreasingagentnotcontaining
CFCsorhalocarbons,see13.2.
-Greasesealinglipsofoilseal,
see13.2.
-Slideoilsealovercrankshaft
stubwithopensidefacing
crankcase.
•
Pressitfullyhomewiththepress
sleeve(1)41128932401.
-Fitflywheel,see5.3.
Starterside:
-Removestartercarrier,see6.6.
-Lightlytaptheoilsealwitha
suitabletubeorpunchtoknockit
outofitsseat.
•
Fitpuller(1)59108904400
(jaws00008933706withprofile
No.3.1).
-Tensionlegs.
-Pulloutoilseal.
Important!Thecrankshaftstub
mustnotbedamaged.
-Cleanthesealingareawithcom-
merciallyavailablesolvent-based
degreasingagentnotcontaining
CFCsorhalocarbons,see13.2.
-Greasesealinglipsofoilseal,
see13.2.
•
Slideassemblysleeve(1)
41128932400overcrankshaft
stub.
-Slideoilsealoverassembly
sleevewithopensidefacing
crankcase.
•
Pressitfullyhomewiththepress
sleeve(1)11158934600.
-Removeassemblysleeve.
-Fitstartercarrier,see6.6.
11
392RA023 VA
11
392RA025 VA
11
392RA005 VA
11
392RA024 VA
11
392RA026 VA
4.3 Oilseals
14
Alwayscheckandrepairthefuel
system,carburetor,airfilterand
ignitionsystembeforelookingfor
faultsontheengine.
Refertomanual"Troubleshooting,
standardrepairs"fortroubleshoo-
tingprocedures.
-Removefanhousingwithpro-
tectivetube,see3.1.
-Removemuffler,see4.1.
-Removecarburetor,see8.2.2.
-Removeignitionmodule,see5.2.
•
Removethrottlecablefrom
tensioner.
•
Removescrews.
-Removespacerflangeand
gasket.
•
Pullscrews(1)outofspacer
flangeifnecessary.
•
Loosenscrew(2)andremove
withbushing.
•
Drawtensioner(3)offspacer
flange.
•
Removeadjustingscrewfrom
tensioner.
Thepartsareassembledinrever-
seorder.
•
Insertscrew(1)withbushing(2).
-Useanewself-lockingnutfor
thescrew.
•
Useanewgasket.
-Tightendownthescrewsofthe
spacerflangetoatorqueof
5.5Nm.
392RA027
VA
392RA028
VA
392RA030
VA
2
392RA031
1
VA
392RA029
1
3
2
1
VA
392RA032
VA
4.4 Exposingthecylinder/
spacerflange
15
-Preparations,see4.4.
•
Unscrewcylinderbasescrews.
Note:Thetwoscrewsattheback
arenotvisible.
-Drawcylinderoffpiston.
-Examinecylinderandreplaceif
necessary.
-Thematchingpistonmustal-
waysbefittedwheninstallinga
newcylinder.Newcylindersare
thereforeonlysuppliedwith
piston.
-Beforeremovingthepiston,de-
cidewhetherthecrankshaftmust
alsoberemoved.Thecrank-
shaftmustbeblockedbysliding
thewoodenassemblyblockbe-
tweenthepistonandcrankcase
inordertoremovetheclutchand
startercarrier.
-Removecylindergasket.
•
Prisethehooklesssnaprings
outoftheannulargrooves.
•
Pushpistonpin(1)outofthe
pistonwithassemblydrift(2)
11148934700.
Note:Ifthepistonpinisstuck,it
canbeloosenedbylightlytap-
pingtheassemblydriftwithaham-
mer.Thepistonmustbeheld
steadyduringthisprocesstoen-
surethatnojoltsaretransmittedto
theconrod.
-Removepistonfromconrodand
drawneedlecageoutofsmall
end.
•
Checkpistonringsandreplaceif
necessary,see4.6.
•
Thoroughlycleansealingarea
(1).
•
Wetneedlecage(2)withoiland
fititinthesmallend.
•
Lightlyheatpistontofacilitatein-
stallationandslipitoverthecon-
rod.
•
Noteinstalledpositionofpiston:
1=Marking
2=Flywheel
•
Pushassemblydriftthrough
pistonandsmallend(needle
cage)withthesmalldiameter
firstandlineupthepiston.
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4.5 Cylinderandpiston
4.5.1 Removal 4.5.2 Installation
16
•
Fitpistonpin(1)onstubofas-
sembly drift (2) and slide it into
the piston (the pin slides home
easily if the piston is hot).
•
Modify sleeve of assembly tool
5910 890 2208 as shown above.
a=35.5mm
b=17.3mm
c = 21.0 mm
•
Insert hookless snap rings with
assembly tool (1) 5910 890 2208.
Note: Refer to manual "Trouble-
shooting, standard repairs" for in-
formation on using the assembly
tool.
•
Fit new cylinder gasket.
•
Lightly oil the piston and piston
rings and rest the piston (1) on
the wooden assembly block (2)
1108 893 4800.
•
Line up the piston rings so that
the radii at the ring gap meet at
thefixingpininthepistongroove.
•
Use clamping strap (1)
0000 893 2600 to enclose piston
and piston rings.
- Ensure that piston rings are
positioned correctly.
- Coat inside of cylinder with oil
and line it up in accordance with
its subsequent installed position.
The piston rings may break if this
is not done.
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17
•
Slidecylinderoverpiston;the
clampingstrapslipsdownward
andthepistonringsslipintothe
cylinder.
-Removeclampingstrapand
assemblyblock.
-Lineupcylinderandcylinder
gasket.
•
Tightencylinderbasescrewsto
atorqueof9.5Nmwithsocket
(1)08125422104.
See4.4forfurtherassemblysteps.
-Removepiston,see4.5.1.
Note:Cokingresiduesmustnot
beallowedtoenterthecrankcase
whenfittingthepistonringsand/or
cleaningthegrooves.
-Removepistonringsfrompiston.
•
Scrapethegroovescleanwitha
pieceofoldpistonring.
•
Fitthenewpistonringsinthe
groovessothattheradiiface
upwards.
-Installpiston,see4.5.2.
-Removecylinder,see4.5.1
•
Unscrewstartercarrierfrom
crankshaftstub.
•
Unscrewclutchfromcrankshaft
stub.
•
Pullflywheeloffcrankshaftstub,
see5.3.
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4.6 Pistonrings4.7Crankcase
4.7.1 Removingthecrankshaft
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18
•
Removepiston,see4.5.1.
•
Unhookguardfromhousing.
•
Removethescrewssecuringthe
twohalvesofthecrankcase.
-Partlyunscrewspindleofassem-
blytoolZS59100072220(left-
handthread).
•
HoldassemblytoolZSagainst
housinghalfonstartersideso
thatthenotchmarked"1"isat
thebottom.
•
Insertscrewsforthestarterco-
verintheholesmarked"15"and
tightenthemdownuntiltheyrest
againsttheperforatedplate.
Note:Assemblyfixtureswithout
holes"14"and"15"canbemodi-
fiedasillustratedabove.
Thediagramshowstheperforated
diskasseenfrombelow.
•
Turnspindle(1)anticlockwise
untilthecrankshafthasbeen
forcedoutofthedeepgroove
ballbearing.Thisalsocauses
thetwohalvesofthehousingto
comeapart.
•
Placesleeve(1)5910893170
(30mm)andsleeves(2)
59108931702(35mm)overthe
holesontheclutch-sidehalfof
thehousing.
-PositionassemblytoolZS
againstthesleevessothatthe
notchmarked"12"isatthe
bottom.
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15
15
1
15
14/6
15
14
15
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19
•
Insert three M5 x 72 bolts in the
holes marked "14".
- Slide washers onto the bolts and
screw on the nuts.
•
Turn spindle (1) anticlockwise
until the crankshaft has been
forced out of the deep groove
ball bearing.
•
Crankshaft (1), conrod (2) and
needle bearing form an insepa-
rable unit and must always be
replaced as a complete unit.
- New deep groove ball bearings
and oil seals must also be fitted
when replacing the crankshaft.
•
Carefully drive the oil seals out
of the crankcase.
•
Press the deep groove ball bea-
ring out of its seat with press
arbor (1) 4119 893 7200.
•
Press the deep groove ball bea-
ring out of its seat with press
arbor (1) 4119 893 7200.
- Examine both halves of the
crankcase for cracks and replace
them.
Both halves of the crankcase can
be replaced if the crankcase is da-
maged.
Each half of the crankcase is supp-
lied with fitted deep groove ball
bearing.
If the original crankcase is used
again, remove the gasket residues
and clean the mating surfaces.
The mating surfaces must be ab-
solutely clean to ensure a perfect
seal.
•
Bushings must be present. New
bushings must be driven into the
crankcase if necessary.
- Heat area of bearing seat on
starter side of crankcase to
approx. 120
°
C.
•
Press deep groove ball bearing
into crankcase by hand as far as
possible.
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4.7.2 Installing the crankshaft
11
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