Stihl 021

Online version - not for reprint
-Removelockingstripfrom
cylinder.
-Insertsparkplugandtighten
downto25Nm(18.5lbf.ft).
•
Ifsparkplughasaseparate
terminalnut,makesureitis
properlytighteneddown.
-Fitbootonthesparkplug.
•
Fittheshuttersothatitslugs
engagetherecessesinthe
handlehousing.
-Installtheairfilter-see10.1.
Thechainbrakeisoneofthemost
importantsafetydevicesonthe
chainsaw.Itsefficiencyis
measuredintermsofthechain
brakingtime,i.e.thetimethat
elapsesbetweenactivatingthe
brakeandthesawchaincoming
toacompletestandstill.The
shorterthebrakingtime,thebetter
theefficiencyandprotection
offeredagainstbeinginjuredby
therotatingchain.
Contamination(withchainoil,
chips,fineparticlesofabrasion,
etc.)andsmoothingofthefriction
surfacesofthebrakebandand
clutchdrumimpairthecoefficient
offriction.This,inturn,reduces
thefrictionalforcesandthus
prolongsthebrakingtime.A
fatiguedorstretchedbrakespring
hasthesamenegativeeffect.
-Starttheengine.
-Withthechainbrakeactivated
(locked),openthrottlewidefor
abriefperiod(max.3seconds)-
thechainmustnotrotate.
-Withthechainbrakereleased,
openthrottlewideandactivate
thebrakemanually-thechain
mustcometoanabrupt
stop.
Note:Thebrakingtimeisin
orderifdecelerationofthe
sawchainisimperceptibleto
theeye.
-Removetheclutchdrum/chain
sprocket-see4.1.
-Releasebrakespringtensionby
pushinghandguardforward.
-Removeupperbumperstripfrom
tensioner.
•
Takeoutthescrews.
-Removethecover.
•
Carefullyeasethebrakespring
offtheanchorpinandtakeitoff
thebellcrank.
4.4 ChainBrake
4.4.1 CheckingFunction 4.4.2 Disassembly
250RA008 VA
VA
135RA026
8 021,023,025