compression ratio YAMAHA WR 250F 2002 Owners Manual

1 - 11
GEN
INFO
CONTROL FUNCTIONS
DECOMPRESSION LEVER
CAUTION:
Never use the decompression lever after
the engine is started. The engine may be
damaged if you use the decompression
lever while it is running.
The decompression lever 1 is located on the
left handlebar and is used when starting the
engine. Squeezing the decompression lever
presses down on the exhaust valve and
releases the pressure in the cylinder head.
This enables the vehicle to be kickstarted
more easily.
EC155001
THROTTLE GRIP
The throttle grip 1 is located on the right han-
dlebar; it accelerates or decelerates the
engine. For acceleration, turn the grip toward
you; for deceleration, turn it away from you.
EC156000
FRONT BRAKE LEVER
The front brake lever 1 is located on the right
handlebar. Pull it toward the handlebar to acti-
vate the front brake.
EC157000
REAR BRAKE PEDAL
The rear brake pedal 1 is located on the right
side of the machine. Press down on the brake
pedal to activate the rear brake.

GEN
INFO
FONCTIONS DES COMMANDES
ARMATUREN UND DEREN FUNKTION
FUNZIONI DI COMANDO
DEKOMPRESSIONSHEBEL
ACHTUNG:
Den Dekompressionshebel unter
keinen Umständen bei laufendem
Motor betätigen. Dies kann den
Motor stark beschädigen.
Wenn der Dekompressionshebel 1
(auf der linken Seite des Lenkers) betä-
tigt wird, öffnet sich das Auslaßventil,
was den Verdichtungsdruck redu-
ziert. Dadurch läßt sich für das Kick-
starten der Kolben leichter über den
Verdichtungstakt hinaus bewegen.
GASDREHGRIFF
Der Gasdrehgriff 1 befindet sich auf
der rechten Seite des Lenkers. Zum
Erhöhen der Motordrehzahl
(Beschleunigung) den Gasdrehgriff
in Gegenfahrtrichtung drehen, zum
Reduzieren der Motordrehzahl den
Gasdrehgriff in Fahrtrichtung drehen.
HANDBREMSHEBEL
Der Handbremshebel 1 zur Betäti-
gung der Vorderradbremse befindet
sich auf der rechten Seite des Len-
kers.
FUSSBREMSHEBEL
Der Fußbremshebel 1 zur Betäti-
gung der Hinterradbremse befindet
sich auf der rechten Fahrzeugseite. LEVIER DE DECOMPRESSION
ATTENTION:
Ne jamais employer le levier de
décompression une fois que le moteur
est mis en marche. Actionner le levier
de décompression lorsque le moteur
tourne risque d’endommager ce der-
nier.
Le levier de décompression 1 se trouve
à la poignée gauche. Celui-ci s’utilise
conjointement avec le kick et facilite la
mise en marche du véhicule. Lorsqu’il
est actionné, le levier de décompression
permet de comprimer la soupape
d’échappement, ce qui réduit la pression
dans la culasse.
POIGNEE DES GAZ
La poignée des gaz 1 est située à la poi-
gnée droite; elle permet d’accélérer ou
de décélérer le moteur. Pour une accélé-
ration, tourner la poignée vers soi; pour
une décélération, la tourner de l’autre
côté.
LEVIER DE FREIN AVANT
Le levier de frein avant 1 se trouve à la
poignée droite. Le tirer vers le guidon
pour actionner le frein avant.
PEDALE DE FREIN ARRIERE
La pédale de frein arrière 1 se trouve du
côté droit de la machine. Appuyer sur la
pédale pour actionner le frein arrière.LEVA DI DECOMPRESSIONE
ATTENZIONE:
Non utilizzare mai la leva di decom-
pressione dopo aver avviato il motore.
Il motore potrebbe danneggiarsi se si
utilizza la leva di decompressione con
il motore in funzione.
La leva di decompressione 1 è posta sul
manubrio sinistro e viene utilizzata
all’avvio del motore. Premendo la leva
di decompressione si abbassa la valvola
di scarico e la pressione viene rilasciata
nella testa del cilindro. Ciò facilita
l’accensione a pedale della moto.
MANOPOLA DELL’ACCELERA-
TORE
La manopola dell’acceleratore 1 è posta
sul manubrio destro e accelera o decelera
il motore. Per l’accelerazione, ruotare la
manopola verso il pilota, per decelerare
ruotarla in senso opposto al pilota.
LEVA DEL FRENO ANTERIORE
La leva del freno anteriore 1 è posta sul
manubrio destro. Tirare verso il manu-
brio per azionare il freno anteriore.
PEDALE DEL FRENO POSTE-
RIORE
Il pedale del freno posteriore 1 è posto
a destra del veicolo. Premere il pedale
del freno per azionare il freno posteriore.
1 - 11

1 - 15
GEN
INFO
STARTING AND BREAK-IN
STARTING AND BREAK-IN
WARNING
Never start or run the engine in a closed
area. The exhaust fumes are poisonous;
they can cause loss of consciousness and
death in a very short time. Always operate
the machine in a well-ventilated area.
CAUTION:
The carburetor on this motorcycle has a
built-in accelerator pump. Therefore,
when starting the engine, do not operate
the throttle or the spark plug will foul.
Unlike a two-stroke engine, this engine
cannot be kick started when the throttle is
open because the kick starter may kick
back. Also, if the throttle is open the air/
fuel mixture may be too lean for the
engine to start.
Never use the decompression lever after
the engine is started. The engine may be
damaged if you use the decompression
lever while it is running.
Before starting the machine, perform the
checks in the pre-operation check list.
STARTING A COLD ENGINE
1. Inspect the coolant level.
2. Turn the fuel cock to “ON”.
3. Shift the transmission into neutral.
4. Fully open the cold starter knob.
5. Without pulling in the decompression
lever, slowly depress the kickstarter
crank until the compression stroke is
found. When considerable resistance of
the kickstarter crank is felt, the engine is
on the compression stroke. If the engine
is on the exhaust stroke, resistance will
only be felt when the kickstarter crank is
initially depressed, not through the entire
range of depression (as when the engine
is on the compression stroke); therefore,
depress the kickstarter crank a few more
times.

GEN
INFO
MISE EN MARCHE ET RODAGE
ANLASSEN UND EINFAHREN
AVVIO E RODAGGIO
6. Den Dekompressionshebel
anziehen und den Kickstarter-
hebel um 10–20˚ heruntertre-
ten.
7. Den Dekompressionshebel los
lassen, dann den Kickstarter-
hebel in Ausgangsstellung zu-
rückstellen und anschließend
den Kickstarterhebel kräftig
durchtreten.
WARNUNG
Den Gasdrehgriff beim Kickstar-
ten nicht öffnen, um ein Rück-
schlagen des Kickstarters zu ver-
meiden.
8. Den Kaltstarterknopf wieder in
die ursprüngliche Stellung zu-
rückschieben und den Motor
bei 3.000 bis 5.000 Umdre-
hungen 1 bis 2 Minuten lang
warmlaufen lassen.
HINWEIS:
Da dieser Vergaser mit einer Be-
schleunigerpumpe ausgestattet ist,
sollte der Motor beim Warmlaufen
nicht hochgedreht werden, um eine
zu starke Anreicherung des Ge-
mischs und ein Absterben des Mo-
tors zu vermeiden. Übrigens darf ein
Viertakter bedenkenlos bei konstan-
ter Drehzahl warmgelaufen werden.
ACHTUNG:
Den Motor nicht zu lange warm-
laufen lassen. 6. Actionner à fond le levier de
décompression et actionner le
kick à un angle de 10 à 20˚.
7. Relâcher le levier de décompres-
sion, relever le kick, puis action-
ner à nouveau ce dernier.
AVERTISSEMENT
Ne pas donner des gaz au moment où
l’on actionne le kick, car celui-ci ris-
que de se relever brutalement.
8. Ramener le bouton de démarrage
à froid à sa position d’origine,
puis faire tourner le moteur à
3.000 à 5.000 tr/mn pendant 1 à 2
minutes.
N.B.:
Puisque ce modèle est équipé d’une
pompe d’accélération, le mélange air/
carburant devient trop riche et le moteur
risque de caler lorsque l’on emballe le
moteur (actionnement successif rapide
de l’accélérateur). A l’inverse d’un
moteur deux temps, ce modèle, comme
tous les quatre temps, peut tourner au
ralenti sans problème.
ATTENTION:
Ne pas laisser le moteur se réchauffer
trop longtemps.6. Tirare la leva di decompressione
verso il manubrio e premere la
pedivella di avviamento di 10 ~
20˚.
7. Rilasciare la leva di decompres-
sione e riportare la pedivella di
avviamento nella sia posizione
originale e quindi agire sulla
pedivella.
AVVERTENZA
Non agire sull’acceleratore mentre si
agisce sulla pedivella di avviamento,
altrimenti la pedivella potrebbe tor-
nare indietro.
8. Riportare la manopola di avvia-
mento a freddo nella sua posi-
zione originale e portare il motore
a 3.000 ~ 5.000 giri/min. per 1 o 2
minuti.
NOTA:
Dal momento che questo modello è
dotato di una pompa di distribuzione, se
il motore viene imballato (acceleratore
aperto e chiuso), la miscela aria/carbu-
rante sarà troppo ricca ed il motore
potrebbe “piantarsi”. Inoltre, a diffe-
renza di un motore a due tempi, questo
modello può girare al minimo.
ATTENZIONE:
Non riscaldare il motore per periodi di
tempo prolungati.
1 - 16

1 - 17
GEN
INFO
STARTING AND BREAK-IN
STARTING A WARM ENGINE
Do not operate the cold starter knob and throt-
tle. Open the hot starter knob (red) and start
the engine by kicking the kickstarter crank
forcefully with a firm stroke.
As soon as the engine starts, push in the hot
starter knob to close the air passage.
Restarting an engine after a fall
Pull the hot starter knob (red) and start the
engine. As soon as the engine starts, push in
the hot starter knob to close the air passage.
The engine fails to start
Pull the hot starter knob (red) all the way out,
pull the decompression lever to the handlebar,
and while holding the lever, kick the kickstarter
crank 10 to 20 times to clear the engine.
Then, restart the engine.
Refer to “Restarting an engine after a fall”.
* Operate the throttle grip before kick starting.
CAUTION:
Observe the following break-in procedures
during initial operation to ensure optimum
performance and avoid engine damage.
Throttle
grip oper-
ation*Cold
starter
knobHot
starter
knob (red)
Starting a cold engine
Air temperature = less than
5 ˚C (41 ˚F)Open 3
or 4 timesON OFF
Air temperature = more
than 5 ˚C (41 ˚F)None ON OFF
Air temperature (normal tem-
perature) = between 5 ˚C
(41 ˚F) and 25 ˚C (77 ˚F)None ON/OFF OFF
Air temperature = more
than 25 ˚C (77 ˚F)None OFF OFF
Starting an engine after a long
period of timeNone ON OFF
Restarting a warm engine None OFF ON
Restarting an engine after a fall None OFF ON

SPEC

2 - 1
GENERAL SPECIFICATIONS
EC200000
SPECIFICATIONS
EC211000
GENERAL SPECIFICATIONS
Model name: WR250FP (USA)
WR250F (EUROPE)
WR250F(P) (CDN, AUS, NZ, ZA)
Model code number: 5PH5 (USA)
5PH6 (EUROPE)
5PH8 (CDN, AUS, NZ, ZA)
Dimensions:
Overall length 2,165 mm (85.2 in)
Overall width 827 mm (32.6 in)
Overall height 1,303 mm (51.3 in)
Seat height 998 mm (39.3 in)
Wheelbase 1,475 mm (58.1 in)
Minimum ground clearance 382 mm (15.0 in)
Basic weight:
With oil and full fuel tank 110.0 kg (242.5 lb)
Engine:
Engine type Liquid cooled 4-stroke, DOHC
Cylinder arrangement Single cylinder, forward inclined
Displacement 249 cm
3

(8.76 Imp oz, 8.42 US oz)
Bore

×

stroke 77.0
×
53.6 mm (3.03
×
2.11 in)
Compression ratio 12.5 : 1
Starting system Kickstarter
Lubrication system: Dry sump
Oil type or grade:
Engine oil (For USA and CDN)
At 5 ˚C (40 ˚F) or higher
Å
Yamalube 4 (20W-40) or SAE 20W-40 type
SH motor oil
(Non-Friction modified)
At 15 ˚C (60 ˚F) or lower
ı

Yamalube 4 (10W-30) or SAE 10W-30 type
SH motor oil
(Non-Friction modified)
and/or
Yamalube 4-R (15W-50)
(Non-Friction modified)
(Except for USA and CDN)
API “SH” or higher grade
-20
-4-10
140
3010
5020
6830
8640 50
104
122°CTemp.
°F
10W-30
10W-40
20W-40
20W-50
15W-40

2

INSP
ADJ
NETTOYAGE DU FILTRE A AIR
LUFTFILTER REINIGEN
PULIZIA FILTRO DELL’ARIA
2. Einstellen:
Dekompressionszugspiel
am Hebeldrehpunkt
Arbeitsschritte
Die Sicherungsmutter 1 lok-
kern.
Die Einstellmutter 2 verdrehen,
bis das vorgeschriebene Spiel
erreicht ist.
Die Sicherungsmutter festzie-
hen.
ACHTUNG:
Nach der Einstellung den Len-
ker bei laufendem Motor beid-
seitig bis zum Anschlag dre-
hen. Dabei darf der Motor nicht
absterben. Der Motor stirbt ab,
wenn der Dekompressionszug
zu wenig Spiel aufweist.
LUFTFILTER REINIGEN
HINWEIS:
Frühzeitige und sachgemäße
Luftfilterwartung hilft, Motorver-
schleiß und -beschädigung vorzu-
beugen.
ACHTUNG:
Den Motor niemals ohne Luftfilter
betreiben, da eindringende Staub-
partikel erhöhten Verschleiß am
Kolben und/oder Zylinder verursa-
chen.
1. Demontieren:
Sitzbank
2. Abziehen:
Rücklicht-Steckverbinder 1
3. Ausbauen:
Luftfiltergehäusedeckel 2
4. Ausbauen:
Schraube 1
Scheibe 2
Luftfiltereinsatz 3
Luftfilter führung 4 2. Régler:
Jeu au levier de décompression
Etapes du réglage:
Desserrer le contre-écrou 1.
Serrer ou desserrer le dispositif de
réglage 2 jusqu’à obtention du jeu
spécifié.
Serrer le contre-écrou.
ATTENTION:
Une fois le réglage effectué, mettre
le moteur en marche et s’assurer
qu’il ne se coupe pas quand le gui-
don est tourné de butée à butée. Si
le câble de décompression est trop
tendu, le système de décompression
va couper le moteur.
NETTOYAGE DU FILTRE A AIR
N.B.:
Un entretien convenable du filtre à air
est la clé pour éviter l’usure prématurée
et l’endommagement du moteur.
ATTENTION:
Ne jamais faire tourner le moteur
lorsque l’élément du filtre à air n’est
pas en place; ceci permettrait la péné-
tration de poussière dans le moteur et
causerait son usure rapide et son
endommagement.
1. Déposer:
Selle
2. Déconnecter:
Le connecteur 1 de la lampe
arrière.
3. Déposer:
Le couvercle 2 du boîtier du
filtre à air.
4. Déposer:
Boulon de fixation 1
Rondelle 2
Elément du filtre à air 3
Guide de filtre à air 42. Regolare:
Gioco della leva della decom-
pressione
Fasi di regolazione:
Svitare il controdado 1.
Ruotare il dispositivo di regola-
zione 2 fino ad ottenere una rego-
lazione idonea.
Serrare il controdado.
ATTENZIONE:
Dopo la regolazione, avviare il
motore e accertarsi che non si
fermi quando si gira completa-
mente il manubrio da entrambi i
lati. Se il cavo di decompressione è
troppo teso, il motore verrà arre-
stato dal sistema di decompres-
sione.
PULIZIA FILTRO DELL’ARIA
NOTA:
Una corretta manutenzione del filtro
dell’aria è il metodo migliore per evitare
un’usura prematura del motore e i danni
conseguenti.
ATTENZIONE:
Non mettere mai in funzione il motore
senza l’elemento filtrante, altrimenti
sporco e polvere penetrerebbero nel
motore causando la rapida usura e
probabili danni al motore.
1. Rimuovere:
Sella
2. Scollegare:
Connettori del cavo del fana-
lino posteriore 1
3. Rimuovere:
Coperchio della scatola del fil-
tro dell’aria 2
4. Rimuovere:
Bullone di montaggio 1
Rondella 2
Elemento del filtro dell’aria 3
Guida del filtro dell’aria 4
3 - 12

3 - 46
INSP
ADJ
LUBRICATION
LUBRICATION
To ensure smooth operation of all compo-
nents, lubricate your machine during setup,
after break-in, and after every race.
1All control cable
2Clutch lever pivot
3Shift pedal pivot
4Footrest pivot
5Throttle-to-handlebar contact
6Drive chain
7Tube guide cable winding portion
8Throttle cable end
9Clutch cable end
0Decompression cable endÅUse Yamaha cable lube or equivalent on these
areas.
ıUse SAE 10W-30 motor oil or suitable chain
lubricants.
ÇLubricate the following areas with high quality,
lightweight lithium-soap base grease.
CAUTION:
Wipe off any excess grease, and avoid get-
ting grease on the brake discs.
AAA
AAB
CC

4 - 26
ENGCAMSHAFTS
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:
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.
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.

4 - 30
ENGCYLINDER HEAD
CYLINDER HEAD
Extent of removal:1 Cylinder head removal
Extent of removal Order Part name Q’ty Remarks
CYLINDER HEAD REMOVAL
Preparation for removal Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
Exhaust pipe and silencer Refer to “EXHAUST PIPE AND
SILENCER” section.
Radiator hose 1 Disconnect at cylinder head side.
Carburetor Refer to “CARBURETOR” section.
Camshaft Refer to “CAMSHAFTS” section.
Upper engine bracket Refer to “ENGINE REMOVAL” section.
1 Radiator pipe 1
2 Decompression cable guide 1
3 Oil delivery pipe 1
4 Nut 2
5 Bolt [L=135 mm (5.31 in)] 2
6 Bolt [L=145 mm (5.71 in)] 2
7 Cylinder head 1 Disconnect the decompression cable.
8 Timing chain guard (exhaust side) 1
9 Bolt (decompression shaft) 1
10 Decompression shaft 1
1