engine YAMAHA YZ125LC 2001 Manual Online

6-2
ELECIGNITION SYSTEM
EC620000
IGNITION SYSTEM
EC621002
INSPECTION STEPS
Use the following steps for checking the possibility of the malfunctioning engine being attributable to
ignition system failure and for checking the spark plug which will not spark.
*Clean or replace
spark plug.
Primary coil
Secondary coil
Repair or replace.
Spark
Check entire ignition
system for connection.
Spark gap test
No good
No good
No good
No good
No good
No good No Spark
Check “ENGINE STOP”
button.
Pick-up coil
Source coil
Check ignition coil.
Check CDI magneto.
Replace CDI unit.
Replace.
Replace.
Replace.
Replace.
Replace.
*marked: Only when the ignition checker is used.
NOTE:
9Remove the following parts before inspection.
1) Seat
2) Fuel tank
9Use the following special tools in this inspection.
Dynamic spark tester:
YM-34487
Ignition checker:
90890-06754Pocket tester:
YU-3112-C/90890-03112
OK
OK
OK
OK
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6-2
ELECSYSTEME D’ALLUMAGE
*Nettoyer ou remplacer
la bougie.
Bobine primaire
Bobine secondaire
Changer ou réparer.
Etincelle
Contrôler du système entierd’allumage
pour les connexions.
Essai de l’intervalle d’étincellement
d’allumage.
Mauvais
Mauvais
Mauvais
Mauvais
Mauvais
Mauvais Pas d’étincelle
Contrôler le bouton d’arrêt du
moteur “ENGINE STOP”.
Bobine d’excitation
Bobine de source
Contrôler la bobine d’allumage.
Contrôler la magnéto CDI.
Changer le bloc CDI.
Changer.
Changer.
Changer.
Changer.
Changer.
O.K.
O.K.
O.K.
O.K.
SYSTEME D’ALLUMAGE
ETAPES DE VERIFICATION
Utiliser les étapes suivantes pour vérifier la possibilité d’attribution du mauvais fonctionnement du
moteur à une panne du circuit d’allumage et pour vérifier la bougie d’allumage qui n’allume pas.
Indication *: Seulement quand le contrôleur d’allumage et utilisé.
N.B.:
9Déposer les pièces suivantes avant de procéder au dépistage des pannes.
1) Selle
2) Réservoir à essence
9Utiliser les outils spéciaux suivants dans ce dépistage des pannes.
Testeur d’étincelle dynamique:
YM-34487
Contrôleur d’allumage:
90890-06754Tester de poche:
YU-3112-C/90890-03112
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6-2
ELECZÜNDANLAGE
*Zündkerze reinigen oder
erneuern.
Primärspule
Sekundärspule
Erneuern oder reparieren.
Zündfunke
Die Anschlüsse der gesamten
Zündanlage kontrollieren.
Test der Zündfunkenstrecke
Nicht in Ordnung
Nicht in Ordnung
Nicht in Ordnung
Nicht in Ordnung
Nicht in Ordnung
Nicht in Ordnung Kein Zündfunke
Den Motorstoppknopf „ENGINE
STOP“ kontrollieren.
Aufnahmespule
Stromspule
Zündspule kontrollieren.
CDI-Magnetzünder kontrollieren.
CDI-Einheit erneuern.
Erneuern.
Erneuern.
Erneuern.
Erneuern.
Erneuern.
In Ordnung
In Ordnung
In Ordnung
In Ordnung
ZÜNDANLAGE
PRÜFVORGÄNGE
Durch folgende Schritte auf eine mögliche Störung des Motors durch einen Defekt im Zündsystem prü-
fen und Ausfindigmachen einer aussetzenden Zündkerze.
Markierung * : Nur wenn das Zündungsprüfgerät verwendet wird.
ANMERKUNG:
9Die folgenden Teile vor Beginn der Störungsbeseitigung ausbauen.
1) Sitz
2) Kraftstofftank
9Die folgenden Spezialwerkzeuge für die Störungsbeseitigung verwenden.
Dynamischer Zündfunkenprüfer:
YM-34487
Zündungsprüfgerät:
90890-06754Taschenprüfgerät:
YU-3112-C/90890-03112
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6-3
ELECIGNITION SYSTEM
EC622001
SPARK GAP TEST
1. Disconnect the spark plug cap from spark
plug.
2. Connect the dynamic spark tester 1(igni-
tion checker 2) as shown.
9Spark plug cap 3
9Spark plug 4
AFor USA and CDN
BExcept 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)
EC624000
COUPLERS AND LEADS CONNECTION
INSPECTION
1. Check:
9Couplers and leads connection
Rust/ Dust/ Looseness/Short-circuit Õ
Repair or replace.
EC625002
“ENGINE STOP” BUTTON INSPECTION
1. Inspect:
9“ENGINE STOP” button conduct
Not continuous while being pushed ÕReplace.
Continuous while being freed ÕReplace.
Minimum spark gap:
6.0 mm (0.24 in)
Tester (+) leadÕBlack/White lead 1
Tester (–) lead
ÕBlack lead 2
B/W B
12
PUSH IN
FREE
Tester selector
position
½´ 1
Œ
º
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6-3
ELEC
SYSTEME D’ALLUMAGE
ZÜNDANLAGE
SISTEMA DI ACCENSIONE
TEST DER ZÜNDFUNKENSTRECKE
1. Den Zündkerzenstecker von der
Zündkerze abtrennen.
2. Den dynamischen Zündfunken-
prüfer 1(Zündungs-Prüfgerät
2) gemäß Abbildung ansch-
ließen.
9Zündkerzenstecker 3
9Zündkerze 4
AFür USA und CDN
BAußer USA und CDN
3. Den Motor mit Hilfe des Kickstar-
ters durchdrehen.
4. Die Zündfunkenstrecke kontrollie-
ren.
5. Den Motor anlassen und die
Zündfunkenstrecke vergrößern,
bis es zu Fehlzündungen kommt.
(nur für USA und CDN)
INSPEKTION DES ANSCHLUSSES
DER KUPPLUNGEN UND KABEL
1. Kontrollieren:
9Anschluß deren Kupplungen
und Kabel
Rost/Staub/Lockerheit/Kurz-
schlußÕReparieren oder
erneuern.
INSPEKTION DES MOTORSTOPP-
KNOPFES „ENGINE STOP“
1. Prüfen:
9Kontakt des Motorstoppknop-
fes „ENGINE STOP“
Kein Stromdurchgang, wenn gedrückt
ÕErneuern.
Stromdurchgang, wenn freigelassen
ÕErneuern.ESSAI DE L’INTERVALLE
D’ETINCELLEMENT
D’ ALLUMAGE
1. Déconnecter le capuchon de bou-
gie de la bougie.
2. Connecter le testeur dynamique
d’étincelle 1(testeur d’allumage
2) comme indiqué.
9Capuchon de bougie 3
9Bougie 4
A Pour USA et CDN
BExcepté pour USA et CDN
3. Actionner la pédale de kick.
4. Contrôler l’écartement d’étincelle
d’allumage.
5. Démarrer le moteur et augmenter
l’intervalle d’étincellement jusqu’à
ce qu’un raté se produise. (unique-
ment USA et CDN)
VERIFICATION DE CONNEXION
DES COUPLEURS ET FILS
1. Contrôler:
9Connexion des coupleurs et fils
Rouille/poussière/desserré/court
-circuit®
Réparer ou changer.
VERIFICATION DU BOUTON
D’ARRET DU MOTEUR “ENGINE
STOP”.
1. Examiner:
9Conductibilité du bouton d’arrêt
du moteur “ENGINE STOP”
Pas de continuité lorsqu’enfoncé Õ
Changer.
Continuité lorsque relâché Õ Changer.
IC622001
TEST DELLA DISTANZA TRA
GLI ELETTRODI
1. Scollegare la calotta della candela
dalla candela.
2. Collegare il tester dinamico delle
scintille 1(apparecchio per il
controllo dell’accensione 2) come
illustrato.
9Calotta della candela 3
9Candela 4
APer USA e CDN
BTranne che per USA e CDN
3. Azionare la pedivella della messa
in moto.
4. Controllare la distanza tra gli elet-
trodi dell’accensione.
5. Avviare il motore e aumentare la
distanza tra gli elettrodi finché non
si verifica uno scatto a vuoto. (sol-
tanto per USA e CDN)
IC624000
ISPEZIONE DEL
COLLEGAMENTO DI
ACCOPPIATORI E CONDUTTORI
1. Controllare:
9Collegamento di accoppiatori e
conduttori
Ruggine/Polvere/Allentamen-
to/Cortocircuito ÕRipararli o
sostituirli.
IC625002
ISPEZIONE DEL PULSANTE
“ARRESTO MOTORE”
1. Ispezionare:
9Comportamento del pulsante
“ARRESTO MOTORE”
Assenza di continuità mentre è premuto
ÕSostituirlo.
Continuità mentre viene rilasciato Õ
Sostituirlo.B/W B
Posizione12del seletto
re del tester
PREM-
11UTO
RILAS-½´ 1
CIATO
Conduttore (+) del tester Õ
Conduttore Nero/Bianco 1
Conduttore (–) del tester Õ
Conduttore Nero 2
Distanza minima tra gli
elettrodi:
6,0 mm (0,24 in)
Ecartement d’étincelle
minimum:
6,0 mm (0,24 in)
Fil (+) de testeur Õ
Fil noir/blanc 1
Fil (–) de testeur Õ
Fil noir 2
B/W BPosition de12sélecteur du
testeur
ENFO-
11NCE
RELA-½´ 1
CHE
Min. Zündfunkenstrecke:
6,0 mm (0,24 in)
Positives (+) Kabel des PrüfgerätesÕ
Schwarz/Weiß Kabel 1
Negatives (–) Kabel des PrüfgerätesÕ
Schwarz Kabel 2
B/W BPosition des12Wahlschaltersam Prüfgerät
GEDR-11ÜCKT
FREIGE-½´ 1
LASSEN
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7-1
TUNSETTING
EC700000
TUNINGEC710000
ENGINEEC711001
Carburetor setting
9The role of fuel is to cool the engine, and in the
case of a 2-stroke engine, to lubricate the
engine in addition to power generation.
Accordingly, if a mixture of air and fuel is too
lean, abnormal combustion will occur, and
engine seizure may result. If the mixture is too
rich, spark plugs will get wet with oil, thus mak-
ing it impossible to bring the engine into full play
or if the worst comes to the worst, the engine
may stall.
9The richness of the air-fuel mixture required for
the engine will vary with atmospheric conditions
of the day and therefore, the settings of the car-
buretor must be properly suited to the atmos-
pheric conditions (air pressure, humidity and
temperature).
9Finally, the rider himself must make a test-run
and check his machine for conditions (pick-up
of engine speed, road surface conditions) and
for the discoloration of the spark plug(s). After
taking these into consideration, he must select
the best possible carburetor settings.
It is advisable to make a note of settings,
atmospheric conditions, road surface condition,
lap-time, etc. so that the memorandum can be
used as a reference useful for future.
EC712000
Atmospheric conditions and carburetor
setting
The reason for the above tendency is that the
richness or leanness of a fuel mixture depends
on the density of the air (i.e. the concentration of
oxygen in it).
Air
Air temp. Humidity pressure Mixture Setting
(altitude)
High HighLow
Richer Leaner
(high)
Low LowHigh
Leaner Richer
(low)
7
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7-2
TUNSETTING
That is:
9Higher temperature expands the air with its
resultant reduced density.
9Higher humidity reduces the amount of oxygen
in the air by so much of the water vapor in the
same air.
9Lower atmospheric pressure (at a high altitude)
reduces the density of the air.
EC713001
Test run
After warming up the engine equipped with the
standard type carburetor(s) and spark plug(s),
run two or three laps of the circuit and check the
smooth operation of the engine and discoloration
of spark plug(s).
ŒNormal
ºOver burned (too lean)
Oil fouled (too rich)
Discoloration Condition of spark plug
NormalInsulator is dry and
burnt brown.
Over burned
Insulator is whitish.
(too lean)
Oil fouled Insulator is sooty and
(too rich) wet.
A
B
C
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7-5
TUNSETTING
EC718010
Jet needle groove position adjustment
Should the engine be hard to run smoothly at
intermediate speeds, the jet needle 1must be
adjusted. If the mixture is too rich or too lean at
intermediate speed operation, irregular engine
operation and poor acceleration will result.
Whether or not the richness of the mixture is
proper is hard to be determined by means of the
spark plug and therefore, it should be judged
from your feeling of actual engine operation.
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 or 0.5 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. In this case, step down the
jet needle clip by one groove or 0.5 groove
and move up the needle to enrich the mix-
ture.
Standard clip position No.3 groove
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7-10
TUNSETTING
EC71C020
Road condition and examples of carburetor setting
EC71D040
Examples of carburetor setting depending on symptom
Symptom Setting Checking
At full throttle Increase main jet calibration No. Discoloration of spark plug
Õ
Stall at high speeds (Gradually) If tan color, it is in good condition.
* Hard breathing If can not be normalized:
Shearing noise Clogged float valve seat
Whitish spark plug Clogged fuel hose
Clogged fuel cock
Lean mixture
At full-throttle Decrease main jet calibration No. Discoloration of spark plug Õ
Stop of speed pick-up (Gradually) If tan color, it is in good condition.
Slow speed pick-up *In case of racing slight enrichment If not effect:
of mixture reduces engine trouble. Clogged air cleaner
Slow response Fuel overflow from carburetor
Sooty spark plug Clogged main air passage or clogged
filter
Rich mixture
Lean mixture Lower jet needle clip position.
(1 groove down)
Rich mixture Raise jet needle clip position.
(1 groove up)
1/4~3/4 throttle Lower jet needle clip position.
* Hard breathing (1 groove down)
Lack of speed
1/4~1/2 throttle Raise jet needle clip position.
Slow speed pick-up (1 groove up)
White smoke
Poor acceleration
Conditions General condition Sandy condition
Under 10°C 15~25°C Over 30°C Under 10°C 15~25°C Over 30°C
(50°F) (59~77°F) (86°F) (50°F) (59~77°F) (86°F)
Parts (Winter)(Spring, Autumn)(Summer) (Winter)(Spring, Autumn)(Summer)
Main jet#470 #460 #450 #490 #480 #470
*#460 *#450 *#440 *#470 *#460 *#450
Jet needle6BGK10-75-3 6BGK9-75-3 6BGK9-75-3 6BGK9-75-4 6BGK10-75-3 6BGK10-75-3
*6BHY25-75-3 *6BHY1-75-3 *6BHY1-75-3 *6BHY1-75-4 *6BHY25-75-3 *6BHY25-75-3
Pilot jet#25 #25 #25 #25 #25 #25
*#30 *#30 *#30 *#30 *#30 *#30
Pilot air screw1 1-1/4 1-1/2 1 1-1/4 1-1/2
*1-1/4 *1-1/2 *1-3/4 *1-1/4 *1-1/2 *1-3/4
Leaner
(Standard)
Richer
Õ
Õ
Clip position indicates the position of jet
needle groove, to which the clip is fitted.
The position is numbered from the top.
If a change in the clip position (1
groove) is effective, try another jet nee-
dle that provides a difference of 0.5 in
the clip position.
*For EUROPE
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7-11
TUNSETTING
Symptom Setting Checking
0~1/4 throttle Use jet needle having a smaller Number of turns-back Õ
* Hard breathing diameter. Correct properly
Speed down Overflow from carburetor
0~1/4 throttle Use jet needle having a larger
Poor acceleration diameter.
White smoke
Unstable at low speeds Lower jet needle clip position.
Pinking noise (1 groove down)
Turn in pilot air screw.
Poor response at extremely Reduce pilot jet calibration No. Dragging brake
low speed Turn out pilot air screw. Overflow from carburetor
If not effect, reverse the
above procedures.
Poor response in Raise jet needle clip position.
the range of low to If no effect, reverse the above
intermediate speeds procedures.
Poor response when Check overall settings. Check air cleaner for fouling.
throttle is opened quickly Use main jet having lower
calibration No.
Raise jet needle clip position.
(1 groove up)
If no effect, reverse the above
procedures.
Poor engine operation Turn in pilot air screw. Check throttle valve operation.
This should be taken simply for an example.
It is necessary to set the carburetor while
checking the operating conditions of the
engine and discoloration of spark plugs.
Normally, carburetor setting is made by
means of the main jet, jet needle clip position
(including one with 0.5 difference), pilot jet
and pilot air screw. If the result of setting is
still unsatisfactory, it is advisable to change
the diameter of the straight portion the jet
needle.
*In case of hard breathing, check the air vent hose for clogging.
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