stop start YAMAHA YZ426F 2002 User Guide

3 - 18
INSP
ADJIDLE SPEED ADJUSTMENT/
VALVE CLEARANCE ADJUSTMENT
EC35M021
IDLE SPEED ADJUSTMENT
1. Start the engine and thoroughly warm it
up.
2. Adjust:
Idle speed
Adjustment steps:
Adjust the pilot screw.
Refer to “PILOT SCREW ADJUSTMENT”
section.
Turn the throttle stop screw 1 until the
engine runs at the lowest possible speed.
To increase idle speed →
Turn the throttle stop screw 1 in a.
To decrease idle speed →
Turn the throttle stop screw 1 out b.
Engine idling speed:
1,700 ~ 1,900 r/min
VALVE CLEARANCE ADJUSTMENT
NOTE:
The valve clearance should be adjusted
when the engine is cool to the touch.
The piston must be at Top Dead Center
(T.D.C.) on compression stroke to check or
adjust the valve clearance.
1. Remove:
Seat
Fuel tank
Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section in the CHAPTER 4.
2. Remove:
Carburetor
Refer to “CARBURETOR” section in
the CHAPTER 4.
Spark plug cap
Engine stay (upper)
Cylinder head cover
Refer to “CAMSHAFTS” section in the
CHAPTER 4.
3. Remove:
Timing plug 1
Straight plug 2
O-ring

4 - 15
ENGCARBURETOR
8. Install:
Throttle shaft assembly 1
Plain washer (metal) 2
Plain washer (resin) 3
Valve lever 4
NOTE:
Apply the fluorochemical grease on the bear-
ings.
Fit the projection a on the throttle shaft
assembly into the slot b in the TPS (throttle
position sensor).
Make sure the stopper c of the spring fits
into the recess in the carburetor.
Turn the throttle shaft assembly left while
holding down the lever 1 5 and fit the throt-
tle stop screw tip d to the stopper e of the
throttle shaft assembly pulley.
ab
1
2
3
4
c
e
d
5
9. Install:
Push rod 1
NOTE:
While holding down the lever 1 2, insert the
push rod farthest into the carburetor.12
10. Install:
Starter jet 1
Pilot jet 2
Spacer 3
Needle jet 4
Main jet 5

6 - 4
–+ELEC

IGNITION SYSTEM
EC622001
SPARK GAP TEST
1. Disconnect the spark plug cap from spark
plug.
2. Connect the dynamic spark tester
1
(ignition checker
2
) as shown.

Spark plug cap
3


Spark plug
4

Å
For USA and CDN
ı
Except for USA and CDN
3. Kick the kick starter.
4. Check the ignition spark gap.
5. Start engine, and increase spark gap until
misfire occurs. (for USA and CDN only)
Minimum spark gap:
6.0 mm (0.24 in)
Å
ı

EC624000
COUPLERS AND LEADS CONNECTION
INSPECTION
1. Check:

Couplers and leads connection
Rust/dust/looseness/short-circuit
→

Repair or replace.
EC625001
“ENGINE STOP” BUTTON INSPECTION
1. Inspect:

“ENGINE STOP” button conduct
No continuity while being pushed
→
Replace.
Continuity while being freed
→
Replace.
Tester (+) lead
→
Black/White lead
1

Tester (–) lead
→
Black lead
2

B/W
1
B
2
Tester selec-
tor position
PUSH IN
Ω

×
1
FREE

–+ELEC

SYSTEME D’ALLUMAGE
ZÜNDANLAGE
ZÜNDFUNKENSTRECKE KONTROLLIEREN
1. Den Zündkerzenstecker von der Zünd-
kerze abziehen.
2. Den Zündfunkenstreckentester
1
(bzw.
2
) wie abgebildet anschließen.

Zündkerzenstecker
3


Zündkerze
4

Å
Nur USA und CAN
ı
Nicht USA und CAN
3. Den Motor mit dem Kickstarter durchdre-
hen.
4. Die Zündfunkenstrecke kontrollieren.
5. Den Motor anlassen und die Zündfunken-
strecke vergrößern, bis es zu Fehlzün-
dungen kommt (nur USA und CAN).
Min. Zündfunkenstrecke
6,0 mm
MOTORSTOPPSCHALTER “ENGINE
STOP” KONTROLLIEREN
1. Kontrollieren:


Motorstoppschalter
(auf Durchgang)
Kein Durchgang bei gedrücktem Schalter
→
Erneuern.
Durchgang bei freigelassenem Schalter
→
Erneuern.
Meßkabel (+)
→
schwarz/weiß
1

Meßkabel (–)
→
schwarz
2

B/W
1
B
2
Meßgerät-
Einstellung
GE-
DRÜCK
Ω × 1
FREI
TEST DE L’INTERVALLE
D’ETINCELLEMENT D’ALLUMAGE
1. Déconnecter le capuchon de bougie de la
bougie.
2. Connecter le testeur dynamique d’étincelle
1 (testeur d’allumage 2) comme indiqué.
Capuchon de bougie 3
Bougie 4
ÅPour les E.-U. et le Canada
ıExcepté pour les E.-U. et le Canada
3. Actionner le démarreur au pied.
4. Contrôler la longueur d’étincelle d’allumage.
5. Démarrer le moteur et augmenter la longueur
d’étincelle jusqu’à ce qu’un raté se produise.
(uniquement E.-U. et Canada)
Longueur d’étincelle minimum:
6,0 mm (0,24 in)
CONTROLE DES CONNEXIONS DE
COUPLEURS ET FILS
1. Contrôler:
Connexion de coupleurs et fils
Rouille/poussière/jeu/court-circuit →
Réparer ou changer.
CONTROLE DU BOUTON D’ARRET DU
MOTEUR “ENGINE STOP”
1. Vérifier:
Continuité du bouton d’arrêt du moteur
“ENGINE STOP”
Pas de continuité lorsqu’enfoncé → Changer.
Continuité lorsque relâché → Changer. Fil (+) de testeur → Fil noir/blanc 1
Fil (–) de testeur → Fil noir 2
B/W
1 B
2 Position de
sélecteur de
testeur
EN-
FONCE
Ω × 1
RE-
LACHE
6 - 4
STECKVERBINDER- UND KABEL-
ANSCHLÜSSE KONTROLLIEREN
1. Kontrollieren:
Steckverbinder- und Kabelanschlüsse
Rost/Staub/Lockerheit/Kurzschluß →
Instand setzen oder erneuern.

6 - 10
–+ELECTPS (THROTTLE POSITION SENSOR) SYSTEM
4. Adjust:
Idle speed
5. Insert the thin electric conductors 2
(lead) into the TPS coupler 1, as shown,
and connect the tester to them.
CAUTION:
Do not insert the electric conductors
more than required because it may
reduce the waterproof function of the
coupler.
Make sure that a short-circuit does not
develop between the terminals because it
may cause damage to electrical compo-
nents.
6. Start the engine.
7. Adjust:
TPS output voltage Adjustment steps:
Attach the inductive tachometer (engine
tachometer) to the high tension cord.
Turn the throttle stop screw 1 until the
specified idle speed.
Refer to “IDLE SPEED ADJUSTMENT”
section in the CHAPTER 3.
Idle speed:
1,700 ~ 1,900 r/min
Tester (+) lead → Yellow lead 3
Tester (–) lead → Black lead 4
Adjustment steps:
Adjust the installation angle of the TPS 1
to obtain the specified output voltage.
NOTE:
Measure the output voltage accurately with a
digital electronic voltmeter that gives an easy
reading of a small voltage.
TPS output
voltageTester selector
position
0.58 ~ 0.78 V DCV

6 - 11
–+ELECTPS (THROTTLE POSITION SENSOR) SYSTEM
8. Tighten:
Screw (TPS) 1
9. Stop the engine.
EC694000
TPS INPUT VOLTAGE INSPECTION
1. Disconnect the TPS coupler.
2. Start the engine.
3. Inspect:
TPS input voltage
Out of specification → Replace the CDI
unit.
Tester (+) lead → Blue lead 1
Tester (–) lead → Black/Blue lead 2
TPS input
voltageTester selector
position
4 ~ 6 V DCV-20

–+ELEC
8. Festziehen:
Schraube (TPS) 1
9. Den Motor stoppen.
PRÜFEN DER TPS-EINGANGSSPANNUNG
1. Die TPS-Steckverbindung trennen.
2. Den Motor starten.
3. Prüfen:
TPS-Eingangsspannung
Außerhalb des Sollwerts → Die CDI-
Einheit austauschen.
Prüfgerätkabel (+) → Blaues Kabel 1
Prüfgerätkabel (–) →
Schwarzes/blaues Kabel 2
TPS-Eingangs-
spannung Prüfgerätein-
stellung
4–6 V DCV-20
8. Serrer:
Vis (TPS) 1
9. Arrêter le moteur.
CONTROLE DE LA TENSION D’ENTREE
DU TPS
1. Débrancher le coupleur de TPS.
2. Démarrer le moteur.
3. Contrôler:
Tension d’entrée du TPS
Hors spécifications → Remplacer le bloc
CDI.
Fil de l’appareil de contrôle (+) → Fil bleu 1
Fil de l’appareil de contrôle (–) →
Fil noir/bleu 2
Tension d’entrée
du TPS Position du sélec-
teur de l’appareil
de contrôle
4 à 6 V DCV-20
6 - 11
SYSTEME TPS (CAPTEUR DU PAPILLON D’ACCELERATION)
TPS-SYSTEM (DROSSELKLAPPEN-POSITIONSSENSOR)

7 - 2
TUN
CAUTION:


The carburetor is extremely sensitive to
foreign matter (dirt, sand, water, etc.).
During installation, do not allow foreign
matter to get into the carburetor.

Always handle the carburetor and its
components carefully. Even slight
scratches, bends or damage to carbure-
tor parts may prevent the carburetor from
functioning correctly. Carefully perform
all servicing with the appropriate tools
and without applying excessive force.

When the engine is stopped or when
riding at no load, do not open and close
the throttle unnecessarily. Otherwise, too
much fuel may be discharged, starting
may become difficult or the engine may
not run well.

After installing the carburetor, check that
the throttle operates correctly and opens
and closes smoothly.
Atmospheric conditions and carburetor
settings
The air density (i.e., concentration of oxygen
in the air) determines the richness or lean-
ness of the air/fuel mixture. Therefore, refer
to the above table for mixture settings.
That is:

Higher temperature expands the air with its
resultant reduced density.

Higher humidity reduces the amount of oxy-
gen in the air by so much of the water vapor
in the same air.

Lower atmospheric pressure (at a high alti-
tude) reduces the density of the air.
Air temp. HumidityAir
pressure
(altitude)Mixture Setting
High High Low (high) Richer Leaner
Low Low High (low) Leaner Richer
SETTING