2003 YAMAHA YZ250F lock

4 - 6
ENG

RADIATOR
EC456000
HANDLING NOTE
WARNING

Do not remove the radiator cap when the
engine and radiator are hot. Scalding hot
fluid and steam may be blown out under
pressure, which could cause serious
injury.
When the engine has cooled, open the radi-
ator cap by the following procedure:
Place a thick rag, like a towel, over the radi-
ator cap, slowly rotate the cap counter-
clockwise to the detent. This procedure
allows any residual pressure to escape.
When the hissing sound has stopped,
press down on the cap while turning coun-
terclockwise and remove it.
EC454000
INSPECTION
EC444100
Radiator
1. Inspect:

Radiator core
1

Obstruction
→
Blow out with com-
pressed air through rear of the radiator.
Bent fin → Repair/replace.
EC455000
ASSEMBLY AND INSTALLATION
Radiator
1. Install:
O-ring 1
Radiator pipe 2
Bolt (radiator pipe) 3
NOTE:
Apply the lithium soap base grease on the O-
ring.
2. Install:
Radiator breather hose 1
Radiator hose 4 (longer) 2
Radiator hose 2 (shorter) 3
To left radiator 4.
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)

ENG
4 - 6
RADIATEUR
KÜHLER
RADIATORE
HANDHABUNGSHINWEIS
WARNUNG
Der heiße Kühler steht unter
Druck. Daher den Kühlerver-
schlußdeckel niemals bei heißem
Motor abnehmen, denn austreten-
der Dampf und heiße Kühlflüssig-
keit könnten ernsthafte Verbrü-
hungen verursachen.
Den Kühlerverschlußdeckel erst
nach Abkühlen des Motors öffnen.
Dazu einen dicken Lappen über
den Kühlerverschlußdeckel legen
und den Deckel langsam gegen
den Uhrzeigersinn bis zum An-
schlag drehen, damit der restliche
Druck entweichen kann. Wenn
kein Zischen mehr zu vernehmen
ist, auf den Deckel drücken und
ihn gegen den Uhrzeigersinn ab-
schrauben.
PRÜFUNG
Kühler
1. Kontrollieren:
Kühlerblock 1
Lamellen zugesetzt → Von
hinten mit Druckluft ausbla-
sen.
Lamellen verformt →
Instand setzen/erneuern.
ZUSAMMENBAU UND MONTAGE
Kühler
1. Montieren:
O-Ring 1
Kühlerleitung 2
Schraube (Kühlerleitung) 3
HINWEIS:
Lithiumfett auf den O-Ring auftragen.
T R..10 Nm (1,0 m · kg)
2. Montieren:
Kühlerlüftungsschlauch 1
Kühlerschlauch 4 (länger) 2
Kühlerschlauch 2 (kürzer) 3
(zum linken Kühler 4) REMARQUES CONCERNANT LA
MANIPULATION
AVERTISSEMENT
Ne jamais enlever le bouchon du
radiateur quand le moteur et le radia-
teur sont chauds. Du liquide bouillon-
nant et de la vapeur risquent de jaillir
sous forte pression, ce qui est très dan-
gereux.
Une fois le moteur refroidi, enlever le
bouchon du radiateur en procédant
comme suit:
Quand le moteur est froid, mettre un
chiffon épais tel qu’une serviette sur
ce bouchon puis le tourner lentement
vers la gauche jusqu’au point de
détente. Cette procédure permet d’éli-
miner toute pression résiduelle.
Quand le sifflement s’est arrêté,
appuyer sur le bouchon tout en le
tournant vers la gauche puis l’enlever.
CONTROLE
Radiateur
1. Contrôler:
Carcasse 1
Encrassé → Nettoyer en souf-
flant de l’air comprimé par
l’arrière du radiateur.
Lamelle tordue → Réparer/
changer.
ASSEMBLAGE ET MONTAGE
Radiateur
1. Monter:
Joint torique 1
Tuyau de radiateur 2
Boulon (tuyau de radiateur) 3
N.B.:
Enduire le joint torique de graisse à base
de savon au lithium.
T R..10 Nm (1,0 m · kg, 7,2 ft · lb)
2. Monter:
Durit de mise à l’air de radia-
teur 1
Durit de radiateur 4 (plus lon-
gue) 2
Durit de radiateur 2 (plus
courte) 3
Au radiateur gauche 4.NOTA PER LA MANIPOLAZIONE
AVVERTENZA
Non rimuovere il tappo del radiatore a
motore e radiatore caldi. Si potrebbe
verificare la fuoriuscita di fluido bol-
lente, che potrebbe provocare infor-
tuni gravi.
Quando il motore si è raffreddato,
aprire il tappo del radiatore nel modo
seguente:
Posizionare uno straccio spesso, ad
esempio un asciugamano, sul tappo
del radiatore e far ruotare lentamente
il tappo in senso opposto al fermo.
Questa procedura consentirà la fuo-
riuscita della pressione residua.
Quando non si sente più il sibilo carat-
teristico, premere sul tappo del radia-
tore e svitarlo in senso antiorario per
rimuoverlo.
ISPEZIONE
Radiatore
1. Ispezionare:
Massa radiante 1
Ostruzioni → Pulire con aria
compressa insufflata dal retro
del radiatore.
Aletta piegata → Riparare/
sostituire.
MONTAGGIO ED INSTALLA-
ZIONE
Radiatore
1. Installare:
O-ring 1
Tubazione del radiatore 2
Bullone (tubazione del radia-
tore) 3
NOTA:
Applicare grasso a base di sapone di litio
sull’O-ring.
T R..10 Nm (1,0 m · kg, 7,2 ft · lb)
2. Installare:
Sfiatatoio radiatore 1
Tubo flessibile radiatore 4 (più
lungo) 2
Tubo flessibile radiatore 2 (più
corto) 3
Sul radiatore sinistro 4.

4 - 8
ENG
CARBURATEUR
VERGASER
CARBURATORE
VERGASER
Demontage-Arbeiten:1 Vergaser demontieren
Demontage-ArbeitenReihen-
folgeBauteil Anz. Bemerkungen
VERGASER DEMONTIEREN
Vorbereitung für den Ausbau Sitzbank und Kraftstofftank Siehe unter “SITZBANK, KRAFTSTOFFTANK UND
SEITENABDECKUNGEN”.
1 Schlauchschelle 1
2 Gaspositionssensor-Leitungskoppler 1
3 Gaszug-Abdeckung 1
4 Gaszug 2
5 Schlauchschelle (Luftfilteranschluß) 1 Die Schrauben (Luftfilterverbindung) lockern.
6 Schlauchschelle (Vergaseranschluß) 2 Die Schrauben (Vergaseranschluß) lockern.
7 Heißstarter-Tauchkolben 1
8 Vergaser (komplett) 1
9 Vergaseranschluß1
1
CARBURATEUR
Organisation de la dépose:1 Dépose du carburateur
Organisation de la dépose Ordre Nom de pièce QtéRemarques
DEPOSE DU CARBURATEUR
Préparation à la dépose Selle et réservoir de carburant Se reporter à la section “SELLE, RESERVOIR DE CAR-
BURANT ET CACHES LATERAUX”.
1 Bride 1
2 Fiche rapide de fil de capteur de position de
papillon des gaz1
3 Cache du logement des câbles de gaz 1
4Câble de gaz 2
5 Bride (raccord de filtre à air) 1 Desserrer la vis (conduit d’admission d’air).
6 Bride (raccord de carburateur) 2 Desserrer les vis (raccord de carburateur).
7 Plongeur de démarrage à chaud 1
8 Rampe de carburateurs 1
9 Raccord de carburateur 1
1
CARBURATORE
Portata dello smontaggio:1 Rimozione del carburatore
Portata dello smontaggio Ordine Denominazione QuantitàOsservazioni
RIMOZIONE DEL CARBURATORE
Preparazione per lo smontaggio Sella e serbatoio del carburante Fare riferimento al paragrafo “SELLA, SERBATOIO
CARBURANTE E CARENATURA LATERALE”.
1 Morsetto 1
2 Accoppiatore cavo del sensore di posizione
dell’acceleratore1
3 Coperchio cavo dell’acceleratore 1
4 Cavo acceleratore 2
5 Morsetto (giunto filtro dell’aria) 1 Svitare la vite (giunto filtro dell’aria).
6 Morsetti (giunto carburatore) 2 Svitare le viti (giunto carburatore).
7 Stantuffo dell’avviamento a caldo 1
8 Gruppo carburatore 1
9 Giunto del carburatore 1
1

4 - 23
ENGCAMSHAFTS
REMOVAL POINTS
Camshaft
1. Remove:
Timing mark accessing screw 1
Crankshaft end accessing screw 2
2. Align:
T.D.C. mark
With align mark.
Checking steps:
Turn the crankshaft counterclockwise with
a wrench.
Align the T.D.C. mark a on the rotor with
the align mark b on the crankcase cover
when piston is at T.D.C. on compression
stroke.
NOTE:
In order to be sure that the piston is at Top
Dead Center, the punch mark c on the
exhaust camshaft and the punch mark d on
the intake camshaft must align with the cyl-
inder head surface, as shown in the illustra-
tion.
3. Remove:
Timing chain tensioner cap bolt 1
Timing chain tensioner 2
Gasket
4. Remove:
Bolt (camshaft cap) 1
Camshaft cap 2
Clip
NOTE:
Remove the bolts (camshaft cap) in a criss-
cross pattern, working from the outside in.
CAUTION:
The bolts (camshaft cap) must be removed
evenly to prevent damage to the cylinder
head, camshafts or camshaft caps.
1
2

4 - 26
ENGCAMSHAFTS
Decompression system
1. Check:
Decompression system
Checking steps:
Check that the decompression mecha-
nism cam 1 moves smoothly.
Check that the decompression mechanism
cam lever pin 2 projects from the camshaft.
Timing chain tensioner
1. Check:
While pressing the tensioner rod lightly
with fingers, use a thin screwdriver 1
and wind the tensioner rod up fully
clockwise.
When releasing the screwdriver by
pressing lightly with fingers, make sure
that the tensioner rod will come out
smoothly.
If not, replace the tensioner assembly.
ASSEMBLY AND INSTALLATION
Camshaft
1. Install:
Exhaust camshaft 1
Intake camshaft 2
Installation steps:
Turn the crankshaft counterclockwise with
a wrench.
NOTE:
Apply the molybdenum disulfide oil on the
camshafts.
Apply the engine oil on the decompression
system.
Squeezing the decompression lever
allows the crankshaft to be turned easily.
Align the T.D.C. mark a on the rotor with the
align mark b on the crankcase cover when
piston is at T.D.C. on compression stroke.

4 - 27
ENGCAMSHAFTS
Fit the timing chain 3 onto both camshaft
sprockets and install the camshafts on the
cylinder head.
NOTE:
The camshafts should be installed onto the
cylinder head so that the punch mark c on
the exhaust camshaft and the punch mark
d on the intake camshaft must align with
the cylinder head surface, as shown in the
illustration.
CAUTION:
Do not turn the crankshaft during the
camshaft installation. Damage or
improper valve timing will result.
Install the clips, camshaft caps 4 and
bolts (camshaft cap) 5.
T R..
Bolt (camshaft cap):
10 Nm (1.0 m • kg, 7.2 ft • lb)
NOTE:
Before removing the clips, cover the cylin-
der head with a clean rag to prevent the
clips from into the cylinder head cavity.
Apply the engine oil on the thread and con-
tact surface of the bolts (camshaft cap).
Tighten the bolts (camshaft cap) in a criss-
cross pattern.
CAUTION:
The bolts (camshaft cap) must be tight-
ened evenly, or damage to the cylinder
head, camshaft caps, and camshaft will
result.
2. Install:
Timing chain tensioner
Installation steps:
While pressing the tensioner rod lightly
with fingers, use a thin screwdriver and
wind the tensioner rod up fully clockwise.

4 - 28
ENG
With the rod fully wound and the chain
tensioner UP mark a facing upward,
install the gasket 1 and the timing chain
tensioner 2, and tighten the bolt 3 to the
specified torque.
T R..
Bolt (timing chain tensioner):
10 Nm (1.0 m • kg, 7.2 ft • lb)
Release the screwdriver, check the ten-
sioner rod to come out and tighten the
gasket 4 and the cap bolt 5 to the speci-
fied torque.
T R..
Tensioner cap bolt:
7 Nm (0.7 m • kg, 5.1 ft • lb)
5
4New
3. Turn:
Crankshaft
Counterclockwise several turns.
4. Check:
Rotor T.D.C. mark
Align with the crankcase align mark.
Camshaft match marks
Align with the cylinder head surface.
Out of alignment → Adjust.
5. Install:
Timing mark accessing screw 1
Crankshaft end accessing screw 2
CAMSHAFTS

4 - 51
ENG

CLUTCH
EC4A3000
REMOVAL POINTS
Clutch boss
1. Remove:

Nut
1


Lock washer
2


Clutch boss
3

NOTE:

Straighten the lock washer tab and use the
clutch holding tool
4
to hold the clutch boss.
Å
For USA and CDN
ı
Except for USA and CDN
Clutch holding tool:
YM-91042/90890-04086
Å
ı

EC4A4000
INSPECTION
EC484100
Clutch housing and boss
1. Inspect:

Clutch housing
1

Cracks/wear/damage
→
Replace.

Clutch boss
2

Scoring/wear/damage
→
Replace.
EC484201
Primary driven gear
1. Check:

Circumferential play
Free play exists
→
Replace.

Gear teeth
a

Wear/damage
→
Replace.
Clutch spring
1. Measure:

Clutch spring free length
a

Out of specification
→
Replace springs
as a set.
Clutch spring free length:
40.4 mm (1.59 in)
: 39.4 mm (1.55 in)