JET YAMAHA YZ250F 2007 User Guide

5 - 64
CHAS
HANDHABUNGSHINWEISE
WARNUNG
Der Stoßdämpfer und Ausgleichs-
behälter enthalten Stickstoff unter
hohem Druck. Deshalb vor Arbei-
ten am Federbein die folgenden
Hinweise sorgfältig lesen und die
Sicherheitsratschläge befolgen.
Der Hersteller übernimmt keinerlei
Haftung für Unfälle, Verletzungen
oder Schäden, die auf unsachge-
mäße Behandlung des Stoßdämp-
fers zurückzuführen sind.
1. Den Stoßdämpfer unter keinen
Umständen öffnen oder mani-
pulieren.
2. Den Stoßdämpfer und Gaszy-
linder von Hitze und offenen
Flammen fern halten Der Stoß-
dämpfer kann aufgrund eines
Stickstoff-Druckanstiegs und/
oder einer Beschädigung des
Schlauchs explodieren.
3. Darauf achten, dass der Aus-
gleichsbehälter nicht beschä-
digt wird. Ein beschädigter
Ausgleichsbehälter beein-
trächtigt die Funktion des
Federbeins.
4. Darauf achten, dass die Gleit-
fläche des Dämpferrohrs nicht
verkratzt wird, um Ölaustritt zu
vermeiden.
5. Der Verschluss an der Unter-
seite des Ausgleichsbehälter
darf unter keinen Umständen
abgenommen werden. Dies ist
außerordentlich gefährlich.
6. Den Stoßdämpfer sachgerecht
(den Hersteller-Anweisungen
entsprechend) entsorgen.
HINWEISE ZUR ENTSORGUNG
(NUR YAMAHA-HÄNDLER)
Vor der Entsorgung muss das Stick-
stoffgas durch das Ventil
1 entfernt
werden. Unbedingt eine Schutzbrille
tragen, um Augenverletzungen durch
ausströmendes Gas oder umherflie-
gende Metallspäne zu vermeiden.
WARNUNG
Die Entsorgung des Stoßdämpfers
sollte am besten dem YAMAHA-
Händler überlassen werden. REMARQUES CONCERNANT LA
MANIPULATION
AVERTISSEMENT
Cet amortisseur arrière est équipé
d’un réservoir indépendant contenant
de l’azote sous haute pression. Afin
d’éviter tout danger d’explosion, lire
attentivement les informations ci-des-
sous avant de manipuler l’amortisseur
arrière.
Le fabricant décline toute responsabi-
lité pour les dommages matériels ou
corporels résultant d’une mauvaise
manipulation.
1. Ne jamais essayer de démonter le
cylindre ou le réservoir.
2. Ne jamais jeter un amortisseur
usagé au feu ou l’exposer à une
chaleur intense. L’amortisseur
arrière risque d’exploser en raison
de la dilatation de l’azote et/ou de
l’endommagement de la durit.
3. Veiller à n’endommager aucune
partie du réservoir de gaz. Un
réservoir endommagé affectera la
capacité d’amortissement ou
entraînera un mauvais fonctionne-
ment.
4. Veiller à ne pas rayer la surface de
contact de la tige de piston avec le
cylindre afin d’éviter tout risque
de fuite d’huile.
5. Ne jamais essayer d’enlever le
bouchon du fond du réservoir
d’azote. Il est très dangereux
d’enlever ce bouchon.
6. Pour la mise au rebut de l’amortis-
seur, suivre les instructions spécifi-
ques.
REMARQUES CONCERNANT LA
MISE AU REBUT
(CONCESSIONNAIRES YAMAHA
UNIQUEMENT)
Avant de mettre l’amortisseur arrière au
rebut, ne pas oublier d’évacuer l’azote
par la soupape 1. Mettre des lunettes
pour se protéger du gaz et/ou des parti-
cules de métal susceptibles de s’échap-
per.
AVERTISSEMENT
Confier la mise au rebut d’un amortis-
seur endommagé ou usé à un conces-
sionnaire Yamaha.NOTA PER LA MANIPOLAZIONE
AVVERTENZA
L’ammortizzatore posteriore è dotato
di un serbatoio di tipo separato riem-
pito con azoto ad alta pressione. Per
prevenire il pericolo di esplosioni, leg-
gere attentamente le informazioni
seguenti prima di maneggiare
l’ammortizzatore.
Il produttore non può essere ritenuto
responsabile di danni a cose o persone
causati da manipolazione impropria.
1. Non manomettere e non tentare
mai di disassemblare il cilindro o il
serbatoio.
2. Mai gettare l’ammortizzatore
posteriore nel fuoco o in una fonte
di forte calore. L’ammortizzatore
potrebbe esplodere a causa
dell’espansione dell’azoto e/o di
danni al flessibile.
3. Fare attenzione a non danneggiare
il serbatoio dell’azoto in nessuna
delle sue parti. Un serbatoio dan-
neggiato compromette l’efficienza
dello smorzamento oppure pro-
voca malfunzionamenti.
4. Fare attenzione a non graffiare la
superficie di contatto dello stelo
del pistone con il cilindro; in caso
contrario potrebbero verificarsi
perdite di olio.
5. Mai tentare di togliere il tappo sul
fondo del serbatoio dell’azoto.
Togliere il tappo è molto perico-
loso.
6. Prima di gettare via l’ammortizza-
tore posteriore, leggere le istru-
zioni di smaltimento.
ISTRUZIONI DI SMALTIMENTO
(SOLO PER I RIVENDITORI
YAMAHA)
Prima di smaltire l’ammortizzatore
posteriore, far fuoriuscire l’azoto dalla
valvola 1. Indossare occhiali protettivi
per evitare ferite agli occhi dovute al gas
liberato e/o a schegge metalliche.
AVVERTENZA
Dovendo smaltire un ammortizzatore
posteriore danneggiato o usurato, con-
segnare il pezzo al proprio rivenditore
Yamaha che eseguirà la procedura di
smaltimento.
AMORTISSEUR ARRIERE
FEDERBEIN
AMMORTIZZATORE POSTERIORE

TUN
ABSTIMMUNG
MOTOR
Vergaser-Abstimmung
Das Gemisch hängt u. a. von den
atmosphärischen Bedingungen ab.
Luftdruck, -temperatur und -feuch-
tigkeit sind Faktoren, die bei der
Vergaser-Abstimmung mit in
Betracht gezogen werden müssen.
Die Leistung und das Ansprech-
verhalten des Motors sowie der
Zustand der Kerze lassen sich am
besten im einem Testlauf prüfen.
Anhand dieser Ergebnisse kann
der Vergaser optimal eingestellt
werden.
HINWEIS:
Es empfiehlt sich, die jeweiligen
Umstände (atmosphärische Bedin-
gungen, Fahrbahnzustand, Anzahl
Runden usw.) und die entsprechen-
den Vergaser-Einstellungen zwecks
späterer Bezugnahme aufzuzeich-
nen.
WARNUNG
Der Vergaser ist ein Bestandteil
des Kraftstoffsystems. Bei
Arbeiten daher stets auf eine
gute Belüftung sorgen und Feu-
erquellen sowie entzündliche
Stoffe fern halten.
Niemals in den Vergasereinlass
hineinblikken. Beim Starten des
Motors könnten Flammen rück-
schlagen. Auch bei ausgebau-
tem Vergaser könnte Benzin aus
der Beschleunigungspumpe
entweichen.
MISE AU POINT
MOTEUR
Réglage du carburateur
Le mélange air/carburant varie en
fonction des conditions atmosphéri-
ques. Il est donc nécessaire de tenir
compte de la pression de l’air, de la
température ambiante, de l’humidité,
etc., pour le réglage du carburateur.
Effectuer un essai de conduite pour
contrôler les performances du moteur
(par ex. la réponse du moteur) et l’état
des bougies (décoloration ou encrasse-
ment). Utiliser les valeurs obtenues
pour effectuer le meilleur réglage pos-
sible du carburateur.
N.B.:
Il est recommandé de conserver un enre-
gistrement de tous les réglages du carbu-
rateur et des conditions extérieures
(conditions atmosphériques, conditions
de la piste/de la surface, temps intermé-
diaire) pour faciliter les réglages ulté-
rieurs du carburateur.
AVERTISSEMENT
Le carburateur fait partie du circuit
d’alimentation. Par conséquent,
veiller à effectuer le montage dans
un endroit bien aéré, à l’écart de
tout objet inflammable ou de toute
source d’incendie.
Ne jamais regarder dans l’admis-
sion du carburateur. Des flammes
peuvent surgir du tuyau en cas de
retour de flamme du moteur au
démarrage. De l’essence peut
s’écouler de l’injecteur de la pompe
de reprise lorsque le carburateur a
été déposé.
MESSA A PUNTO
MOTORE
Impostazione carburatore
La miscela aria/carburante varia a
seconda delle condizioni atmosferi-
che. Di conseguenza, durante la rego-
lazione del carburatore è necessario
tenere in considerazione la pressione
dell’aria, la temperatura
dell’ambiente, l’umidità ecc.
Eseguire un giro di prova per control-
lare l’efficienza del motore (ad es. la
reattività dell’acceleratore) e la pre-
senza di macchie o incrostazioni sulla/
e candela/e. Utilizzare queste letture
per determinare la migliore imposta-
zione possibile del carburatore.
NOTA:
Si consiglia di prendere nota di tutte le
impostazioni del carburatore e delle con-
dizioni esterne (ad es. condizioni atmo-
sferiche, condizioni del percorso e della
superficie, tempi per ogni giro) per sem-
plificare le successive impostazioni del
carburatore.
AVVERTENZA
Il carburatore fa parte del circuito
del carburante. Di conseguenza,
assicurarsi di installarlo in un
ambiente ben ventilato, lontano da
sostanze infiammabili e da ogni
fonte di fuoco.
Non guardare mai all’interno
dell’aspirazione del carburatore. Se
durante l’avvio il motore ha un
ritorno di fiamma, potrebbero svi-
lupparsi fiamme dal tubo. Quando
si toglie il carburatore, l’ugello della
pompa acceleratore può scaricare
benzina.
REGLAGE
EINSTELLUNG
REGISTRAZIONE
7 - 1





7

7 - 3
TUNSETTING
Effects of the setting parts on the throttle
valve opening
ÈClosed
ÉFully open
1Pilot screw/pilot jet
2Throttle valve cutaway
3Jet needle
4Main jet
1/2 3/4 1/4 1/8
1
2
3
4
ÈÉ
Main system
The FLATCR carburetor has a primary main
jet. This type of main jet is perfect for racing
machines since it supplies an even flow of fuel,
even at full load. Use the main jet and the jet
needle to set the carburetor.
Pilot system
The FLATCR carburetor is manufactured with
a pilot screw. The pilot screw adjustment
ranges from fully closed throttle to 1/4 open
throttle.

7 - 4
TUNSETTING
1Jet needle
2Pilot air jet
3Needle jet
4Main jet
5Pilot jet
6Pilot screw
Main jet adjustment
The richness of the air-fuel mixture at full throt-
tle can be set by changing the main jet 1
.
If the air-fuel mixture is too rich or too lean, the
engine power will drop, resulting in poor accel-
eration.
Effects of changing the main jet (reference)
ÈIdle
ÉFully open
Standard main jet #178
1/4 1/2 3/4
+10%
#178
–10%
#180
#175
ÈÉ

7 - 5
TUNSETTING
Pilot screw adjustment
The richness of the air-fuel mixture with the
throttle fully closed to 1/4 open can be set by
turning the pilot screw 1. Turning in the pilot
screw will make the mixture lean at low
speeds, and turning it out will enrich it.
* Except for USA and CDN
NOTE:
•If the engine idling speed fluctuates, turn the
pilot screw only 1/2 of a turn in either direc-
tion.
•To optimize the fuel flow at a smaller throttle
opening, each machine’s pilot screw has
been individually set at the factory. Before
adjusting the pilot screw, turn it in fully and
count the number of turns. Record this num-
ber as the factory-set number of turns out.
Effects of adjusting the pilot screw (refer-
ence)
ÈIdle
ÉFully open
12 turns out
23 turns out
32-1/2 turns out
Standard pilot screw
position (example)1-7/8
* 2-1/8
1
1/4 1/2 3/4
+5%
–5%
1
23
ÈÉ
Pilot jet adjustment
The richness of the air-fuel mixture with the
throttle open 1/4 or less can be set by adjust-
ing the pilot jet 1.
Standard pilot jet #42

7 - 6
TUNSETTING
Effects of adjusting the pilot jet (reference)
ÈIdle
ÉFully open
1/4 1/2 3/4
+5%
–5%
#45
#40#42
ÈÉ

Jet needle groove position adjustment
Adjusting the jet needle 1 position affects the
acceleration when the throttle is 1/8 to 3/4
open.
1. Too rich at intermediate speeds
Rough engine operation is felt and the
engine will not pick up speed smoothly. In
this case, step up the jet needle clip by one
groove and move down the needle to lean
out the mixture.
2. Too lean at intermediate speeds
The engine breathes hard and will not pick
up speed quickly.
Step down the jet needle clip by one
groove and move up the needle to enrich
the mixture.
Effects of changing the jet needle groove
position (reference)
ÈIdle
ÉFully open
1No.4 groove
2No.2 groove
3No.3 groove
Standard clip position No.4 groove
1/4 1/2 3/4
+10%
–10%
1
23
ÈÉ

7 - 7
TUN
Jet needle adjustment
The jet needle is adjusted by changing it.
The tapered sections of all jet needles have
the same starting positions, but the needles
are available with different straight-portion
diameters.

OBEPQ - 4
Clip position
Diameter a of straight portion Standard jet needle OBEPQ
Effects of changing the jet needle (refer-
ence)
(Diameter of the straight portion)
Changing the diameter of the straight portion
adjusts the air-fuel mixture when the throttle is
1/8 to 1/4 open.
ÈIdle
ÉFully open
Relationship with throttle opening
The flow of the fuel through the carburetor
main system is controlled by the main jet and
then, it is further regulated by the area
between the main nozzle and the jet needle.
The fuel flow relates to the diameter of the
straight portion of the jet needle with the throt-
tle 1/8 to 1/4 open and relates to the clip posi-
tion with the throttle 1/8 to 3/4 open.
Therefore, the fuel flow is balanced at each
stage of throttle opening by the combination of
the jet needle straight portion diameter and clip
position.
+10 %
Q
–10 %P
R
1/4 1/2 3/4 ÈÉ
SETTING

7 - 8
TUN
Leak jet adjustment (accelerator pump
adjustment)
The leak jet 1 is a setting part that adjusts the
flow of fuel discharged by the accelerator
pump. Since the accelerator pump operates
only when throttle is open, the leak jet is used
to adjust a fuel mixture ratio for quick throttle
opening and is therefore different from other
setting parts that adjust a fuel mixture for each
throttle opening (each engine speed).
1. The engine breathes hard in quick throttle
opening.
Select a leak jet having lower calibrating
No. than standard to enrich the mixture.
#80 → #70
2. Rough engine operation is felt in quick
throttle opening.
Select a leak jet having higher calibrating
No. than standard to lean out the mixture.
#80 → #90
* Except for USA and CDNStandard leak jet#80
* #701
SETTING

7 - 9
TUNSETTING
EC71Q000
Carburetor setting parts
* Except for USA and CDNPart name Size Part number
Main jet Rich
(STD)
Lean#188
#185
#182
#180
#178
#175
#172
#170
#1684MX-14943-95
4MX-14943-44
4MX-14943-94
4MX-14943-43
4MX-14943-93
4MX-14943-42
4MX-14943-92
4MX-14943-41
4MX-14943-91
Pilot jet Rich
(STD)
Lean#48
#45
#42
#40
#384MX-14948-06
4MX-14948-05
4MX-14948-04
4MX-14948-03
4MX-14948-02
Jet needle Rich
(STD)
LeanOBEPM
OBEPN
OBEPP
OBEPQ
OBEPR
OBEPS
OBEPT5NL-14916-PM
5NL-14916-PN
5NL-14916-PP
5NL-14916-P1
5NL-14916-PR
5NL-14916-PS
5NL-14916-PT
Leak jet Rich
(STD)
Lean#50
#60
#70
#80
#90
#100
#1104JT-1494F-07
4JT-1494F-11
4JT-1494F-15
4JT-1494F-19
4JT-1494F-23
4JT-1494F-27
4JT-1494F-29
* Leak jet Rich
(STD)
Lean#40
#50
#60
#70
#80
#90
#1004JT-1494F-03
4JT-1494F-07
4JT-1494F-11
4JT-1494F-15
4JT-1494F-19
4JT-1494F-23
4JT-1494F-27

7 - 10
TUN
Examples of carburetor setting depending on symptom
This should be taken simply for an example. It is necessary to set the carburetor while checking
the operating conditions of the engine.
Symptom Setting Checking
At full throttle
Hard breathing
Shearing noise
Whitish spark plug
Lean mixtureIncrease main jet calibration no.
(Gradually)Discoloration of spark plug
→
If tan color, it is in good condition.
If cannot be corrected:
Clogged float valve seat
Clogged fuel hose
Clogged fuel cock
Check that the accelerator pump oper-
ates smoothly.
At full throttle
Speed pick-up stops
Slow speed pick-up
Slow response
Sooty spark plug
Rich mixtureDecrease main jet calibration no.
(Gradually)Discoloration of spark plug
→
If tan color, it is in good condition.
If cannot be corrected:
Clogged air filter
Fuel overflow from carburetor
Lean mixture Lower jet needle clip position.
(1 groove down)
The clip position is the jet needle
groove on which the clip is installed.
The positions are numbered from the
top.
Check that the accelerator pump oper-
ates smoothly. (except for rich mixture
symptom). Rich mixture Raise jet needle clip position.
(1 groove up)
1/4 ~ 3/4 throttle
Hard breathing
Lack of speedLower jet needle clip position.
(1 groove down)
1/4 ~ 1/2 throttle
Slow speed pick-up
Poor accelerationRaise jet needle clip position.
(1 groove up)
Closed to 1/4 throttle
Hard breathing
Speed downUse jet needle with a smaller diame-
ter.Slow-speed-circuit passage
Clogged
→ Clean.
Overflow from carburetor
Closed to 1/4 throttle
Poor accelerationUse jet needle with a larger diameter.
Raise jet needle clip position.
(1 groove up)
Poor response in the low to
intermediate speedsRaise jet needle clip position.
If this has no effect, lower the jet nee-
dle clip position.
Poor response when throttle
is opened quicklyCheck overall settings.
Use main jet with a lower calibration
no.
Raise jet needle clip position.
(1 groove up)
If these have no effect, use a main jet
with a higher calibration no. and lower
the jet needle clip position.Check air filter for fouling.
Check that the accelerator pump oper-
ates smoothly.
Jet needleClip
Groove 7 Groove 6
Groove 5
Groove 4
Groove 3
Groove 2
Groove 1
Leaner
↑
(Standard)
↓
Richer
*
SETTING