2003 YAMAHA YZ125LC transmission

4-68
ENGCRANKCASE AND CRANKSHAFT
6. Install:
9Holder 1
9Bolt (holder) 2
7. Install:
9Segment 1
9Bolt (segment) 2
NOTE:
9When installing the segment onto the shift cam
3, align the punch mark awith the dowel pin
b.
9Turn the segment clockwise until it stops and
tighten the bolt.
8. Remove:
9Sealant
Forced out on the cylinder mating surface.
9. Apply:
9Engine oil
To the crank pin, bearing, oil delivery hole
and connecting rod big end washer.
10. Check:
9Crankshaft and transmission operation
Unsmooth operation Repair.
30 Nm (3.0 m•kg, 22 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)

4-69
ENGTRANSMISSION, SHIFT CAM AND SHIFT FORK
Extent of removal Order Part name Q’ty Remarks
TRANSMISSION, SHIFT CAM AND
SHIFT FORK REMOVAL
Preparation for EngineRefer to “ENGINE REMOVAL” section.
removal Separate the crankcase. Refer to“CRANKCASE AND CRANK
SHAFT
” section.
1 Guide bar (long) 1
2 Guide bar (short) 1
3 Shift cam 1
4 Shift fork 3 1
5 Shift fork 1 1
6 Shift fork 2 1
7 Main axle 1
8 Drive axle 1Refer to “REMOVAL POINTS”.
9 Spacer 1
EC4H0000
TRANSMISSION, SHIFT CAM AND SHIFT FORK
Extent of removal:1Shift cam and shift fork removal2Main axle and drive axle removal
1
2



10 Nm (1.0 m•kg, 7.2 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)

4-70
ENGTRANSMISSION, SHIFT CAM AND SHIFT FORK
EC4H3000
REMOVAL POINTS
EC4H3200
Transmission
1. Remove:
9Main axle 1
9Drive axle 2
NOTE:
9Tap lightly on the transmission drive axle with a
soft hammer to remove.
9Remove assembly carefully. Note the position
of each part. Pay particular attention to the lo-
cation and direction of shift forks.
EC4H4000
INSPECTION
EC4H4200
Gears
1. Inspect:
9Matching dog a
9Gear teeth b
9Shift fork groove c
Wear/Damage Replace.
2. Check:
9Gears movement
Unsmooth movement 
Repair or replace.
EC4H4600
Bearing
1. Inspect:
9Bearing 1
Rotate inner race with a finger.
Rough spot/Seizure Replace.

4-71
ENGTRANSMISSION, SHIFT CAM AND SHIFT FORK
EC4H4801
Shift fork, shift cam and segment
1. Inspect:
9Shift fork 1
Wear/Damage/Scratches Replace.
2. Inspect:
9Shift cam 1
9Segment 2
9Guide bar 3
Bend/Wear/Damage Replace.
3. Check:
9Shift fork movement
On its guide bar.
Unsmooth operation Replace shift fork
and/or guide bar.
NOTE:
For a malfunctioning shift fork, replace not only
the shift fork itself but the two gears each adja-
cent to the shift fork.
EC4H5000
ASSEMBLY AND INSTALLATION
EC4H5213
Transmission
1. Install:
95th pinion gear (23T) 1
93rd pinion gear (19T) 2
94th pinion gear (19T) 3
92nd pinion gear (15T) 4
To main axle 5.
NOTE:
9Apply the molybdenum disulfide oil on the 4th
and 5th pinion gears inner circumference and
on the end surface.
9Apply the molybdenum disulfide oil on the 2nd
and 3rd pinion gears inner circumference.

4-72
ENGTRANSMISSION, SHIFT CAM AND SHIFT FORK
2. Install:
93rd wheel gear (29T) 1
94th wheel gear (24T) 2
92nd wheel gear (28T) 3
95th wheel gear (25T) 4
91st wheel gear (30T) 5
To drive axle 6.
NOTE:
9Apply the molybdenum disulfide oil on the 1st,
2nd and 3rd wheel gears inner circumference
and on the end surface.
9Apply the molybdenum disulfide oil on the 4th
and 5th wheel gears inner circumference.
3. Install:
9Plain washer 1
9Circlip 2
NOTE:
9Be sure the circlip sharp-edged corner ais po-
sitioned opposite side to the plain washer and
gear b.
9Be sure the circlip end cis positioned at axle
spline groove d.
4. Install:
9Spacer 1
NOTE:
9Apply the lithium soap base grease on the oil
seal lip.
9When installing the spacer into the crankcase,
pay careful attention to the crankcase oil seal
lip.

4-73
ENGTRANSMISSION, SHIFT CAM AND SHIFT FORK
EC4H5312
Shift cam and shift fork
1. Install:
9Shift fork 1 (L) 1
9Shift fork 2 (C) 2
9Shift fork 3 (R) 3
NOTE:
9Mesh the shift fork #1 (L) with the 4th wheel
gear 4and #3 (R) with the 5th wheel gear 6
on the drive axle.
9Mesh the shift fork #2 (C) with the 3rd pinion
gear 5on the main axle.
2. Install:
9Shift cam 1
NOTE:
9Apply the transmission oil on the shift cam.
9Install the shift cam while holding up the 4th
wheel gear 2and keeping the shift fork #1 3
moved in the direction of the arrow.
3. Install:
9Guide bar (short) 1
9Guide bar (long) 2
NOTE:
9Apply the transmission oil on the guide bars.
9Be sure the long bar is inserted into the shift
forks #1 and #3 and the short one into #2.
5. Install:
9Main axle 1
9Drive axle 2
NOTE:
Apply the transmission oil on the crankcase
bearings.

4-73
ENG
BOITE A VITESSES, BARILLET DE SELECTEUR ET FOURCHETTE
GETRIEBE, SCHALTNOCKE UND SCHALTGABEL
TRASMISSIONE, CAMMA DEL CAMBIO E FORCELLA DEL CAMBIO
Schaltnocke und Schaltgabel
1. Einbauen:
9Schaltgabel 1 (L) 1
9Schaltgabel 2 (C) 2
9Schaltgabel 3 (R) 3
HINWEIS:
9Die Schaltgabel Nr. 1 (L) mit dem
Hauptwellen-Zahnrad für den 4.
Gand 4und die Schaltgabel Nr. 3
(R) mit dem Hauptwellen-Zahnrad
für den 5. Gang 6in Eingriff brin-
gen.
9Die Schaltgabel Nr. 2 (C) mit dem
Vorgelegewelle-Zahnrad für den 3.
Gang 5in Eingriff bringen.
2. Einbauen:
9Schaltnocke 1
HINWEIS:
9Das Getriebeöl auf Schaltnocke auf-
tragen.
9Schaltnocke einbauen indem man
das 4. Zahnrad 2hoch und die
Schaltgabel 3in der Pfeilrichtung in
Bewegung hält.
3. Einbauen:
9Führungsstange (Kurze) 1
9Führungsstange (Lange) 2
HINWEIS:
9Getriebeöl auf den Führungsstangen
auftragen.
9Darauf achten, daß die lange Stange
in die Schaltgabeln Nr. 1 und Nr. 3
und die kurze Stange in die Schalt-
gabel Nr. 2 eingesetzt wird.
Barillet de sélecteur et fourchette
1. Monter:
9Fourchette 1 (L) 1
9Fourchette 2 (C) 2
9Fourchette 3 (R) 3
N.B.:
9Engrener la fourchette N°1 (L) avec le
pignon de roue de 4éme 4et la four-
chette N°3 (R) avec le pignon de
5éme 6de l’arbre moteur.
9Engrener la fourchette N°2 (C) avec
le pignon de 3éme 5de l’arbre prin-
cipal.
2. Monter:
9Barillet de sélecter 1
N.B.:
9Appliquer l’huile de transmission sur
le barillet.
9Installez la came d’inverseur tout en
maintenant le 4e pignon 2et la four-
chette d’inverseur n˚ 1 3dans le sens
de la flèche.
3. Monter:
9Barre de guidage (petite) 1
9Barre de guidage (longue) 2
N.B.:
9Appliquer de l’huile de boîte de
vitesses sur les barres guidages.
9Vérifier que la barre longue est situé
dans les fourchettes N°1 et 3 et la
petite dans le numéro 2.
IC4H5312Camma del cambio e forcella del
cambio
1. Installare:
9Forcella del cambio 1 (L) 1
9Forcella del cambio 2 (C) 2
9Forcella del cambio 3 (R) 3
NOTA:
9Ingranare la forcella del cambio No. 1
(L) con l’ingranaggio a ruota della 4a
4e la No. 3 (R) con l’ingranaggio a
ruota della 5a6sull’asse motore.
9Ingranare la forcella del cambio No. 2
(C) con l’ingranaggio a pignone della
3
a5sull’asse principale.
2. Installare:
9Camma del cambio 1
NOTA:
9Applicare sulla camma del cambio
l’olio per trasmissioni.
9Installare la camma del cambio tenen-
do sollevato l’ingranaggio a ruota 2
della quarta, con la forcella del cam-
bio n° 1 3spostata nella direzione
della freccia.
3. Installare:
9Barra di scorrimento (corta) 1
9Barra di scorrimento (lunga) 2
NOTA:
9Applicare l’olio per trasmissioni sulle
barre di scorrimento.
9Assicurarsi che la barra lunga sia
inserita nelle forcelle del cambio No.
1 e No. 3 e quella corta nella No. 2.
5. Monter:
9Axe principal 1
9Axe moteur 2
N.B.:
Appliquez de l’huile de transmission
sur les paliers du carter.
5. Einbauen:
9Hauptwelle 1
9Vorgelegewelle 2
HINWEIS:
Getriebeöl auf die Lager der Kurbel-
gehäuses auftragen.
5. Installare:
9Asse principale 1
9Asse motore 2
NOTA:
Applicare ai cuscinetti del carter l’olio
per trasmissioni.

4-74
ENGTRANSMISSION, SHIFT CAM AND SHIFT FORK
4. Check:
9Shifter operation
9Transmission operation
Unsmooth operation Repair.