2004 YAMAHA YZ125LC engine

2-3
SPECMAINTENANCE SPECIFICATIONS
Item Standard Limit
Cylinder head:
Combustion chamber capacity 10.05 cm
3…
(0.354 Imp oz, 0.340 US oz)
Warp limit…
0.03 mm (0.0012 in)
Cylinder:
Bore size 54.000~54.014 mm 54.1 mm (2.130 in)
(2.1260~2.1265 in)
Taper limit…
0.05 mm (0.0020 in)
Out of round limit…
0.01 mm (0.0004 in)
Piston:
Piston size/ 53.957~53.972 mm…
(2.1243~2.1249 in)
Measuring point* 17.5 mm (0.69 in)…
Piston clearance 0.040~0.045 mm 0.1 mm (0.004 in)
(0.0016~0.0018 in)
Piston offset 1.0 mm (0.039 in)/EX-side…
Piston pin:
Piston pin outside diameter 14.995~15.000 mm 14.975 mm
(0.5904~0.5906 in) (0.5896 in)
Piston ring:
Sectional sketch Plain…
B=1.0 mm (0.039 in)…
T=2.35 mm (0.093 in)…
End gap (installed) 0.5~0.7 mm (0.020~0.028 in) 1.2 mm (0.047 in)
Side clearance (installed) 0.035~0.070 mm 0.1 mm (0.004 in)
(0.0014~0.0028 in)
Crankshaft:
Crank width “A” 55.90~55.95 mm …
(2.201~2.203 in)
Runout limit “C” 0.03 mm (0.0012 in) 0.05 mm (0.0020 in)
Connecting rod big end
side clearance “D” 0.20~0.70 mm (0.008~0.028 in)…
Small end free play “F” 0.8~1.0 mm (0.031~0.039 in) 2.0 mm (0.08 in)
Clutch:
Friction plate thickness 2.9~3.1 mm (0.114~0.122 in) 2.8 mm (0.110 in)
Quantity 8 …
Clutch plate thickness 1.5~1.7 mm (0.059~0.067 in) …
Quantity 7 …
Warp limit … 0.2 mm (0.008 in)
Clutch spring free length 41.2 mm (1.622 in) 39.2 mm (1.543 in)
Quantity 5 …
Clutch housing thrust clearance 0.20~0.25 mm (0.008~0.010 in) …
Clutch housing radial clearance 0.015~0.049 mm …
(0.0006~0.0019 in)
Clutch release method Outer pull, rack and pinion pull …
EC212000
MAINTENANCE SPECIFICATIONSEC212100
ENGINE
5XE-9-30-2A 5/10/03 1:57 PM Page 4

2-10
SPECMAINTENANCE SPECIFICATIONS
Part to be tightened Thread size Q'tyT ightening torqueNm m•kg ft•lb
Rear brake master cylinder and frame M 6 ×1.0 2 10 1.0 7.2
Rear brake master cylinder cap M 4 ×0.7 2 2 0.2 1.4
Rear brake hose union bolt (caliper) M10 ×1.25 1 30 3.0 22
Rear brake hose union bolt (master cylinder) M10 ×1.25 1 30 3.0 22
Rear wheel axle and nut M20 ×1.5 1 125 12.5 90
Nipple (spoke) – 72 3 0.3 2.2
Driven sprocket and wheel hub M 8 ×1.25 6 42 4.2 30
Disc cover and rear brake caliper M 6 ×1.0 2 7 0.7 5.1
Protector and rear brake caliper M 6 ×1.0 2 7 0.7 5.1
Chain puller adjust bolt and locknut M 8 ×1.25 2 16 1.6 11
Engine mounting:
Engine and frame (front) M10 ×1.25 1 64 6.4 46
Engine and frame (lower) M10 ×1.25 1 64 6.4 46
Engine bracket and frame M 8 ×1.25 2 34 3.4 24
Engine bracket and engine M 8 ×1.25 1 34 3.4 24
Pivot shaft and nut M16 ×1.5 1 85 8.5 61
Relay arm and swingarm M14 ×1.5 1 80 8.0 58
Relay arm and connecting rod M14 ×1.5 1 80 8.0 58
Connecting rod and frame M14 ×1.5 1 80 8.0 58
Rear shock absorber and frame M10 ×1.25 1 56 5.6 40
Rear shock absorber and relay arm M10 ×1.25 1 53 5.3 38
Rear frame and frame (upper) M 8 ×1.25 1 32 3.2 23
Rear frame and frame (lower) M 8 ×1.25 2 29 2.9 21
Swingarm and brake hose holder M 5 ×0.8 4 1 0.1 0.7
Swingarm and patch M 4 ×0.7 4 2 0.2 1.4
Chain tensioner mounting M 8 ×1.25 2 19 1.9 13
Chain support and swingarm M 6 ×1.0 3 7 0.7 5.1
Seal guard and swingarm M 5 ×0.8 4 6 0.6 4.3
Fuel tank mounting M 6 ×1.0 2 10 1.0 7.2
Fuel tank and fuel cock M 6 ×1.0 2 7 0.7 5.1
Fuel tank and seat set bracket M 6 ×1.0 1 7 0.7 5.1
Fuel tank and hooking screw (fitting band) M 6 ×1.0 1 7 0.7 5.1
Fuel tank and fuel tank bracket M 6 ×1.0 4 7 0.7 5.1
Air scoop mounting M 6 ×1.0 6 4 0.4 2.9
Front fender mounting M 6 ×1.0 4 7 0.7 5.1
Rear fender mounting (front) M 6 ×1.0 2 7 0.7 5.1
Rear fender mounting (rear) M 6 ×1.0 2 12 1.2 8.7
Side cover mounting M 6 ×1.0 2 7 0.7 5.1
Seat mounting M 8 ×1.25 2 19 1.9 13
Number plate M 6 ×1.0 1 7 0.7 5.1
NOTE:

- marked portion shall be checked for torque tightening after break-in or before each race.


 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5XE-9-30-2A 5/10/03 1:57 PM Page 11

2-12
SPEC
GENERAL TORQUE SPECIFICATIONS/
DEFINITION OF UNITS
This chart specifies torque for standard faste-
ners with standard I.S.O. pitch threads. Torque
specifications for special components or assem-
blies are included in the applicable sections of
this book. To avoid warpage, tighten multi-faste-
ner assemblies in a crisscross fashion, in pro-
gressive stages, until full torque is reached.
Unless otherwise specified, torque specifications
call for clean, dry threads. Components should
be at room temperature.
A: Distance across flats
B: Outside thread diameter
EC230000
DEFINITION OF UNITS
EC220001
GENERAL TORQUE SPECIFICATIONS
A B TORQUE SPECIFICATION
(Nut) (Bolt)
Nm m•kg ft•lb
10 mm 6 mm 6 0.6 4.3
12 mm 8 mm 15 1.5 11
14 mm 10 mm 30 3.0 22
17 mm 12 mm 55 5.5 40
19 mm 14 mm 85 8.5 61
22 mm 16 mm 130 13 94
Unit Read Definition Measure
mm milimeter 10-
3meter Length
cm centimeter 10-2meter Length
kg kilogram 103gram Weight
N Newton 1 kg ×m/sec2Force
Nm Newton meter N ×m Torque
m•kg Meter kilogrma m ×kg Torque
Pa Pascal N/m2Pressure
N/mm Newton per millimeter N/mm Spring rate
L Liter — Volume or capacity
cm3Cubic centimeter — Volume or capacity
r/min Revolution per minute — Engine speed
5XE-9-30-2A 5/10/03 1:57 PM Page 13

2-13
SPECCABLE ROUTING DIAGRAM
EC240000
CABLE ROUTING DIAGRAM
1Brake hose
2Cable guide
3“ENGINE STOP” button lead
4Fuel tank breather hose
5Clamp
6Throttle cable
7Wireharness
8YPVS breather hose
9Radiator breather hose
0CDI magneto lead
q“ENGINE STOP” button lead
connector
wAir vent hose (left)
eOverflow hose
rAir vent hose (right)
tTransmission oil breather hoseAFasten the ground lead
together with the front
installation portion of the
ignition coil.
BPass the throttle cable and
“ENGINE STOP” button lead
into the cable guide. Align
with the cable guide the
front end of the tape on the
throttle cable.
CPass the fuel tank breather
hose between the handlebar
and tension bar, then insert
its end into the hole of the
number plate.
DPass the throttle cable and
“ENGINE STOP” button lead
over the radiator hose.
EClamp the throttle cable,
“ENGINE STOP” button lead
and wireharness to the main
pipe.FPass the wireharness on the
outside of the “ENGINE STOP”
button lead.
GClamp the throttle cable and
wireharness to the main pipe.
HPass the transmission oil
breather hose, air vent hoses
and overflow hose between
the frame and connecting rod.
IPass the radiator breather
hose and YPVS breather hose
outside the engine bracket
and inside the down tube. Then
pass the radiator breather
hose inside the YPVS
breather hose.
JClamp the radiator breather
hose and CDI magneto lead
on the rear of the down-tube.
5XE-9-30-2B 5/10/03 1:57 PM Page 26

2-13
SPEC
SCHEMA DE CHEMINEMENT DES CABLES
KABELFÜHRUNGSÜBERSICHTPLAN
DIAGRAMMA DEL PASSAGGIO DEI CAVI
KABELFÜHRUNGSÜBER-
SICHTPLAN
1Bremsschlauch
2Kabelführung
3Leitungskabel des Motorstoppknopfes
„ENGINE STOP“
4Kraftstofftank-Belüftungsschlauch
5Klemme
6Gasseil
7Kabelbaum
8YPVS-Belüftungsschlauch
9Kühler-Belüftungsschlauch
0Leitungskabel des CDI-Magnetzünders
qLeitungskabel-Steckverbinder des
Motorstoppknopfes „ENGINE STOP“
wBelüftungsschlauch (Links)
eÜberlaufschlauch
rBelüftungsschlauch (Rechts)
tGetriebeöl-Belüftungsschlauch
ADas Massekabel gemeinsam mit dem
vorderen Befestigungsteil der Zündspu-
le befestigen.
BDas Gasseil und den Leitungsdraht der
„ENGINE STOP“-Taste durch die
Kabelführing führen.
Vorderes Bandende am Gaskabel mit
der Kabelführung ausrichten.
CDen Kraftstofftank-Belüftungsschlauch
zwischen der Lenkstange und der Zug-
stange durchführen und danach sein
Ende in die Bohrung des Nummern-
schildes einsatzen.
DDas Gasseil und das Leitungskabel des
Motorstoppknopfes „ENGINE STOP“
über dem Kühlerschlauch durchführen.
EGaskabel, Motorstoppknopf „ENGINE
STOP“ und Kabelbaum am Hauptrohr
festklemmen.
FDen Kabelbaum an der Außenseite des
Leitungskabels des Motorstoppknopfes
„ENGINE STOP“ vorbei führen.
GGaskabel und Kabelbaum am Haupt-
rohr festklemmen.
HDen Getriebeöl-Belüftungsschlauch, die
Belüftungsschläuche und den Üderlauf-
schlauch zwischen dem Rahmen und
der Verbindungsstange durchführen.
IKühlerbelüftungsschlauch und YPVS-
Belüftungsschlauch an der Aussenseite
der Motorhalterung und an den Innen-
seite des Abwärtsrohrs führen. Dann
Kühlerbelüftungsschlauch in den YPVS-
Belüftungsschlauch einführen.
JDen Kühler-Belüftungsschlauch und
das Leitungskabel des CDI-Magnetzün-
ders an der Rückseite des Fallrohres
festklemmen.
SCHEMA DE
CHEMINEMENT DES
CABLES
1Tuyau de frein
2Guide de câble
3Fil de bouton d’arrêt du moteur “ENGINE
STOP”
4Tuyau de reniflard de réservoir à essence
5Bride
6Câble d’accélérateur
7Faisceau de fils
8Tube de reniflard YPVS
9Tuyau de reniflard de radiateur
0Fil de magnéto CDI
qConnecteur du fil du bouton d’arrêt du
moteur “ENGINE STOP”
wTuyau de ventilation (gauche)
eTube de trop-plein
rTuyau de ventilation (droit)
tTuyau de reniflard d’huile de boîte de
vitesses
åFixer le fil de masse avec la partie avant de
fixation de la bobine d’allumage.
∫Faire passer le câble d’accélérateur et le fil
du bouton “ENGINE STOP” (arrêt
moteur) dans le guidage de câble.
Aligner sur le guide-câble l’extrémité
avant du ruban du câble d’accélérateur.
çFaire passer le tuyau de reniflard du réser-
voir à carburant entre le guidon et la barre
de tension, puis l’insérer dans l’orifice de
la plaque minéralogique.
∂Faire passer le câble d’accélérateur et le fil
du bouton d’arrêt moteur “ENGINE
STOP” au-dessus de la durit de radiateur.
´Fixez le câble d’accélérateur, le fil du
bouton “ENGINE STOP” et le faisceau
de fils sur le tube principal.
ƒFaites passer le faisceau de fils à l’exté-
rieur du fil du bouton d’arrêt du moteur
“ENGINE STOP”.
©Bridez le câble d’accélérateur et le fais-
ceau de fils sur le tube principal.
˙Faire passer le tube reniflard d’huile de
transmission, les tubes d’aération et le tube
de trop-plein.
ˆFaites passer le tuyau du reniflard du
radiateur et le tuyau du reniflard de
l’YPVS à l’extérieur du support du
moteur et à l’intérieur du tube inférieur.
Faites ensuite passer le tuyau du reniflard
du radiateur à l’intérieur tuyau du reni-
flard de l’YPVS.
∆Fixer avec un collier le tuyau de reniflard
du radiateur et le fil de magnéto CDI.
IC240000
DIAGRAMMA DEL
PASSAGGIO DEI CAVI
1Tubo flessibile del freno
2Guida per cavi
3Conduttore del pulsante “ARRESTO
MOTORE”
4Sfiato del serbatoio del carburante
5Brida
6Cavo dell’acceleratore
7Complesso conduttori
8Sfiato YPVS
9Sfiato del radiatore
0Conduttore del magneto CDI
qConnettore del conduttore del pulsante
“ARRESTO MOTORE”
wTubo flessibile dello sfiatatoio dell’aria
(sinistro)
eTubo flessibile di troppopieno
rTubo flessibile dello sfiatatoio dell’aria
(destro)
tSfiato dell’olio per trasmissioni
åFissare il conduttore di terra con la parte
della bobina di accensione installata
anteriormente.
∫Far passare il cavo dell’acceleratore e il
conduttore del pulsante “ARRESTO
MOTORE” nella guida per cavi.
Allineare con la guida per cavi l’estre-
mità anteriore del nastro sul cavo dell'ac-
celeratore.
çFar passare lo sfiato del serbatoio puran-
te fra il manubrio e il tirante, quindi inse-
rirne l’estremità nel foro della targa.
∂Far passare il cavo dell’acceleratore e il
conduttore del pulsante “ARRESTO
MOTORE” sopra il manicotto flessibile
del radiatore.
´Assicurare al tubo principale il cavo
dell’acceleratore e il conduttore e il
cablaggio preassemblato del pulsante
“ARRESTO MOTORE”.
ƒFar passare il cablaggio preassemblato
dal lato esterno del conduttore del pul-
sante “ARRESTO MOTORE”.
©Assicurare al tubo principale il cavo del-
l'acceleratore e il cablaggio preassembla-
to.
˙Far passare lo sfiato dell’olio per tra-
smissioni, i tubi flessibili degli sfiatatoi
dell’aria e il tubo flessibile di troppopie-
no fra il telaio e la leva di rinvio.
ˆFar passare lo sfiato del radiatore e lo
sfiato YPVS fuori dalla staffa del motore
dentro il tubo inferiore. Quindi far passa-
re lo sfiato del radiatore dentro lo sfiato
dell’YPVS.
∆Bloccare lo sfiato del radiatore e il con-
duttore del magnete CDI sul retro del
tubo rivolto verso il basso.
5XE-9-30-2B 5/10/03 1:57 PM Page 27

2-17
SPECCABLE ROUTING DIAGRAM
AInstall the brake hose so that its pipe portion
directs as shown and lightly touches the
projection on the master cylinder.
BPass the “ENGINE STOP” button lead in
the middle of the clutch holder.
CPass the clutch cable in front of the throttle
cable.
DClamp the “ENGINE STOP” button lead to
the handlebar to 3 clicks.
EPass the brake hose in front of the number
plate and through the cable guide.
FCross the clutch cable and throttle cable
over the number plate boss. 1Brake hose
2Master cylinder
3“ENGINE STOP” button lead
4“ENGINE STOP” button
5Throttle cable
6Clutch cable
7Clamp
8Cable guide
5XE-9-30-2B 5/10/03 1:57 PM Page 34

2-17
SPEC
SCHEMA DE CHEMINEMENT DES CABLES
KABELFÜHRUNGSÜBERSICHTPLAN
DIAGRAMMA DEL PASSAGGIO DEI CAVI
1Bremsschlauch
2Hauptbremszylinder
3Leitungskabel des Motorstoppknopfes
„ENGINE STOP“
4Motorstoppknopf „ENGINE STOP“
5Gasseil
6Kupplungskabel
7Klemme
8Kabelführung
ADen Bremsschlauch so einbauen, daß
sein Rohrteil gemäß Abbildung ange-
ordnet ist und den Überstand am
Hauptbremszylinder leicht berührt.
BDas Leitungskabel des Motorstopp-
knopfes „ENGINE STOP“ in der Mitte
des Kupplungshalters durchführen.
CDas Kupplungsseil vor dem Gasseil
durchführen.
DKabel des Motorausschaltknopfes am
Lenker festklemmen mit 3 klicks.
EDen Bremsschlauch vor dem Num-
mernschild und durch die Kabelführung
durchführen.
FDas Kupplungsseil und das Gasseil
über der Nummernschild-Befesti-
gungsnabe überkreuzen.1Tuyau de frein
2Maître-cylindre
3Fil de bouton d’arrêt du moteur “ENGI-
NE STOP”
4Bouton d’arrêt du moteur “ENGINE
STOP”
5Câble d’accélérateur
6Câble d’embrayage
7Bride
8Guide de câble
åIstaller la tuyau de frein de manière que
la partie avec le tuyau soit dirigée
comme indipué et touche légèrement la
saillie sur le maîtrecylindre.
∫Faire passer le fil de bouton d’arrêt du
moteur “ENGINE STOP” au centre du
support d’embrayage.
çFaire passer le câble d’embrayage devant
le câble d’accélérateur.
∂Fixer le fil du bouton “ENGINE STOP”
sur le guidon (3 déclics).
´Faire passer le tuyau de frein devant la
plaque d’immatriculation et à travers le
guide de câble.
ƒCroiser le câble d’embrayage et le câble
d’accélérateur sur le bossage de fixation
de la plaque minéralogique.1Tubo flessibile del freno
2Cilindro principale
3Conduttore del pulsante “ARRESTO
MOTORE”
4Pulsante “ARRESTO MOTORE”
5Cavo dell’acceleratore
6Cavo della frizione
7Nastro
8Guida per cavi
åInstallare il tubo flessibile del freno in
modo che la sua parte di tubo sia rivolta
come illustrato e tocchi leggermente la
sporgenza sul cilindro principale.
∫Far passare il conduttore del pulsante
“ARRESTO MOTORE” nel mezzo del
supporto della frizione.
çFar passare il cavo della frizione davanti
al cavo dell’acceleratore.
∂Bloccare il conduttore del pulsante
“ARRESTO MOTORE” sul manubrio
dopo 3 scatti.
´Far passare il tubo flessibile del freno
davanti alla targa e attraverso la guida
per cavi.
ƒIncrociare il cavo della frizione e il cavo
dell’acceleratore sopra il mozzo della
targa.
5XE-9-30-2B 5/10/03 1:57 PM Page 35

3-4
PRE-OPERATION INSPECTION AND MAINTENANCE
INSP
ADJ
EC320000
PRE-OPERATION INSPECTION AND MAINTENANCE
Before riding for break-in operation, practice or a race, make sure the machine is in good operating
condition.
Before using this machine, check the following points.
EC321000
GENERAL INSPECTION AND MAINTENANCE
Item Routine Page
Coolant Check that coolant is filled up to the radiator filler cap.
Check the cooling system for leakage.P3-5~9
Fuel Check that a fresh mixture of oil and gasoline is filled in
the fuel tank. Check the fuel line for leakage.P1-12
Transmission oil Check that the oil level is correct. Check the crankcase
for leakage.P3-12~14
Gear shifter and clutch Check that gears can be shifted correctly in order and
that the clutch operates smoothly.P3-9
Throttle grip/Housing Check that the throttle grip operation and free play
are correctly adjusted. Lubricate the throttle grip and P3-10~11
housing, if necessary.
Brakes Check the play of front brake and effect of front and
rear brake.P3-17~23
Chain Check chain slack and alignment. Check that the chain
is lubricated properly.P3-24~26
Wheels Check for excessive wear and tire pressure. Check for
loose spokes and have no excessive play.P3-34~35
Steering Check that the handlebar can be turned smoothly and
have no excessive play.P3-35~36
Front forks and Check that they operate smoothly and there is no oil
rear shock absorber leakage.P3-26~33
Cables (wires) Check that the clutch and throttle cables move smooth-
ly. Check that they are not caught when the handlebars —
are turned or when the front forks travel up and down.
Muffler Check that the muffler is tightly mounted and has no
cracks.P3-15~16
Sprocket Check that the driven sprocket tightening bolt is
not loose.P3-24
Lubrication Check for smooth operation. Lubricate if necessary. P3-37
Bolts and nuts Check the chassis and engine for loose bolts and nuts. P1-16
Lead connectors Check that the CDI magneto, CDI unit, and ignition coil
are connected tightly.P1-6
Settings Is the machine set suitably for the condition of the
racing course and weather or by taking into account the
P7-1~25
results of test runs before racing? Are inspection and
maintenance completely done?
5XE-9-30-3A 4/28/03 5:55 PM Page 14