2002 YAMAHA YZ125LC Cylinder

4-28
ENGCYLINDER HEAD, CYLINDER AND PISTON
3. Install:
9Nut (cylinder) 1
NOTE:
Tighten the nuts in stage, using a crisscross pat-
tern.
4. Install:
9Collar 1
9Push rod 2
9Plain washer 3
9Bolt (push rod) 4
NOTE:
9Set the collar 5included in owner's tool kit to
install the bolt (push rod).
9Do not forget to remove the collar.
EC4753A1
Cylinder head and cylinder
1. Apply:
9Engine oil
To piston 1, piston ring 2and cylinder
surface.
2. Install:
9Cylinder 1
cC
Make sure the piston ring is properly posi-
tioned. Install the cylinder with one hand
while compressing the piston ring with the
other hand.
NOTE:
After installing, check the smooth movement of
the piston.
30 Nm (3.0 m•kg, 22 ft•lb)
5 Nm (0.5 m•kg, 3.6 ft•lb)
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4-28
ENG
CULASSE, CYLINDER ET PISTON
ZYLINDERKOPF, ZYLINDER UND KOLBEN
TESTA CILINDRO, CILINDRO E PISTONE
3. Einbauen:
9Mutter (Zylinder) 1
HINWEIS:
Die Muttern überkreuz in mehreren
Schritten festziehen.
4. Einbauen:
9Hülse 1
9Schubstange 2
9Beilegescheibe 3
9Schraube (Schubstange) 4
HINWEIS:
9Die im Werkzeugsatz enthaltene
Hülse 5einsetzen, um die Schrau-
be (Schubstange) einzubauen.
9Danach nicht vergessen, die Hülse
zu entfernen.
3. Installare:
9Dado (cilindro) 1
NOTA:
Serrare i dadi in sequenza, usando uno
schema incrociato.
4. Installare:
9Piattello 1
9Asta di spinta 2
9Rosetta 3
9Bullone (asta di spinta) 4
NOTA:
9Per installare il bullone (asta di spin-
ta), collocare il piattello 5incluso nel
kit di utensili del proprietario.
9Non dimenticare di togliere il piattel-
lo.
Zylinderkopf und Zylinder
1. Auftragen:
9Motoröl
Auf Kolben 1, Kolbenring 2
und Zylinderfläche.
2. Einbauen:
9Zylinder 1
dD
Darauf achten, daß der Kolbenring
richtig positioniert ist.
Zylinderblock mit einer Hand
anbringen, während der Kolbenring
mit der anderen Hand zusammen-
gedrückt wird.
HINWEIS:
Nachdem das Leistungsventil einge-
baut wurde, dieses auf glatte Bewe-
gung prüfen.
Culasse et cylindre
1. Appliquer:
9Huile du moteur
Sur le piston 1, le segment 2
et la surface de cylindre.
2. Monter:
9Cylindre 1
fF
Veiller à positionner le segment cor-
rectement.
Mettre d’une main, le cylindre en
place tout en comprimant le segment
de l’autre.
N.B.:
Après avoir monter, contrôler si elle se
déplace régulièrement.
3. Monter:
9Ecrou (cylindre) 1
N.B.:
Serrer les écrous par étapes en utilisant
un modèle déntre croisement.
4. Monter:
9Collerette 1
9Champignon de débrayage 2
9Rondelle plain 3
9Boulon (champignon de débra-
yage) 4
N.B.:
9Poser le collet 5fourni dans la trous-
se d’outils pour mettre le boulon en
place (champignon de débrayage).
9Ne pas oublier d’enlever le collet.
IC4753A1Testa cilindro e cilindro
1. Applicare:
9Olio per motori
Sul pistone 1, sulla fascia ela-
stica 2e sulla superficie del
cilindro.
2. Installare:
9Cilindro 1
iI
Assicurarsi che la fascia elastica sia
posizionata correttamente. Installare
il cilindro con una mano comprimen-
do allo stesso tempo la fascia elastica
con l’altra mano.
NOTA:
Dopo l’installazione, controllare che il
pistone si muova senza difficoltà.
30 Nm (3,0 m•kg, 22 ft•lb)
5 Nm (0,5 m•kg, 3,6 ft•lb)
30 Nm (3,0 m•kg, 22 ft•lb)
5 Nm (0,5 m•kg, 3,6 ft•lb)
30 Nm (3,0 m•kg, 22 ft•lb)
5 Nm (0,5 m•kg, 3,6 ft•lb)
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4-29
ENGCYLINDER HEAD, CYLINDER AND PISTON
7. Install:
9Cylinder head 1
9Copper washer 2
9Nut (cylinder head) 3
NOTE:
Tighten the nuts (cylinder head) in stage, using a
crisscross pattern.
8. Install:
9Engine bracket 1
9Bolt (engine bracket) 2
9CDI unit bracket 3
9Engine mounting bolt (upper) 4
9. Install:
9Spark plug 1
9Spark plug cap 2
9Radiator hose 2 3
28 Nm (2.8 m•kg, 20 ft•lb)
34 Nm (3.4 m•kg, 24 ft•lb)
34 Nm (3.4 m•kg, 24 ft•lb)
20 Nm (2.0 m•kg, 14 ft•lb)
5. Install:
9Gasket (power valve housing)
9Power valve housing 1
9Bolt (power valve housing) 2
6. Install:
9O-ring 1
NOTE:
Apply the lithium soap base grease on the O-
rings.
5 Nm (0.5 m•kg, 3.6 ft•lb)
1 Nm (0.1 m•kg, 0.7 ft•lb)
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4-29
ENG
CULASSE, CYLINDER ET PISTON
ZYLINDERKOPF, ZYLINDER UND KOLBEN
TESTA CILINDRO, CILINDRO E PISTONE
6. Einbauen:
9O-Ring 1
HINWEIS:
Das Lithiumfett auf O-Ringe auftra-
gen.
6. Installare:
9Anello di tenuta 1
NOTA:
Applicare sugli anelli di tenuta il grasso
a base di sapone di litio.
7. Einbauen:
9Zylinderkopf 1
9Kupferscheibe 2
9Mutter (Zylinderkopf) 3
HINWEIS:
Die Muttern (Zylinderkopf) überkreuz
in mehreren Schritten festziehen.
7. Installare:
9Testa cilindro 1
9Rondella in rame 2
9Dado (testa cilindro 3
NOTA:
Serrare i dadi (testa cilindro) in sequen-
za, usando uno schema incrociato.
8. Einbauen:
9Motorhalterung 1
9Schraube (Motorhalterung) 2
9CDI-Halter 3
9Motor-Befestigungsschraube
(Ober) 48. Installare:
9Staffa del motore 1
9Bullone (staffa del motore 2
9Staffa dell’unità CDI 3
9Bullone di montaggio del moto-
re (superiore) 4
9. Einbauen:
9Zündkerze 1
9Zünderzenstecker 2
9Kühlerschlauch 2 39. Installare:
9Candela 1
9Calotta della candela 2
9Manicotto flessibile del radiato-
re 2 3
5. Einbauen:
9Dichtung (Leistungsventil-
gehäuse)
9Leistungsventilgehäuse 1
9Schraube (Leistungsventil-
gehäuse) 25. Monter:
9Joint (boîtier de clapet de puis-
sance)
9Boîtier de chapet de puissance
1
9Boulon (boîtier de clapet de
puissance) 2
6. Monter:
9Joint torique 1
N.B.:
Appliquer de la graisse à base de savon
au lithium sur le joint torique.
7. Monter:
9Culasse 1
9Rondelle en cuivre 2
9Ecrou (culasse) 3
N.B.:
Serrer les écrous (culasse) par étapes en
utilisant un modéle d’entre croisement.
8. Monter:
9Support du moteur 1
9Boulon (support du moteur) 2
9Support du bloc CDI 3
9Boulon de montage du moteur
(supérieur) 4
9. Monter:
9Bougie 1
9Capuchou de bougie 2
9Tuyau du radiateur 2 35. Installare:
9Guarnizione (corpo della valvo-
la di potenza)
9Corpo della valvola di potenza
1
9Bullone (corpo della valvola di
potenza) 2
5 Nm (0,5 m•kg, 3,6 ft•lb)
5 Nm (0,5 m•kg, 3,6 ft•lb)
28 Nm (2,8 m•kg, 20 ft•lb)
34 Nm (3,4 m•kg, 24 ft•lb)
34 Nm (3,4 m•kg, 24 ft•lb)
20 Nm (2,0 m•kg, 14 ft•lb)
28 Nm (2,8 m•kg, 20 ft•lb)
34 Nm (3,4 m•kg, 24 ft•lb)
34 Nm (3,4 m•kg, 24 ft•lb)
20 Nm (2,0 m•kg, 14 ft•lb)
5 Nm (0,5 m•kg, 3,6 ft•lb)
28 Nm (2,8 m•kg, 20 ft•lb)
34 Nm (3,4 m•kg, 24 ft•lb)
34 Nm (3,4 m•kg, 24 ft•lb)
20 Nm (2,0 m•kg, 14 ft•lb)
1 Nm (0,1 m•kg, 0,7 ft•lb)1 Nm (0,1 m•kg, 0,7 ft•lb)
1 Nm (0,1 m•kg, 0,7 ft•lb)
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4-38
ENG
KICK AXLE, SHIFT SHAFT AND PRIMARY DRIVE
GEAR
Extent of removal Order Part name Q’ty Remarks
RPIMARY DRIVE GEAR REMOVAL
Preparation for Drain the transmission oil.Refer to “TRANSMISSION OIL REPLACE-
removalMENT“ section in the CHAPTER 3.
Clutch cable Disconnect at engine side.
Bolt (brake pedal) Shift the brake pedal downward.
Radiator hose 4 Disconnect at water pump side.
Bolt (push rod)
Refer to “CYLINDER HEAD, CYLINDER
AND PISTON” section.
1 Kick starter 1
2 Crankcase cover (right) 1
3 Bolt (Primary drive gear) 1 Only loosening
Refer to “REMOVAL POINTS”.
4 Primary driven gear 1 Refer to “CLUTCH AND PRIMARY
DRIVEN GEAR”section.
5 Primary drive gear 1
EC4C0000
KICK AXLE, SHIFT SHAFT AND PRIMARY DRIVE GEAREC4C8000PRIMARY DRIVE GEAR
1
Extent of removal:1Primary drive gear removal
10 Nm (1.0 m•kg, 7.2 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
55 Nm (5.5 m•kg, 40 ft•lb)
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4-57
ENGENGINE REMOVAL
Extent of removal Order Part name Q’ty Remarks
ENGINE REMOVAL
Preparation for
Hold the machine by placing the
removalsuitable stand under the engine.
Seat and fuel tankRefer to “SEAT, FUEL TANK AND
SIDE COVERS” section.
Carburetor Refer to “CARBURETOR AND REED
VALVE” section.
Exhaust pipe and silencer Refer to “EXHAUST PIPE AND
SILENCER” section.
Clutch cable Disconnect at engine side.
Radiator hose 2 Disconnect at cylinder head side.
Radiator hose 4 Disconnect at water pump side.
Bolt (radiator) Refer to “RADIATOR” section.
Radiator hose 3 Disconnect at right side radiator,
then shift the radiators forward.
Spark plug cap
Disconnect the CDI magneto lead.
EC4M0000
ENGINE REMOVAL
w
Support the machine securely so there is no dan-
ger of it falling over.
26 Nm (2.6 m•kg, 19 ft•lb)
34 Nm (3.4 m•kg, 24 ft•lb)
69 Nm (6.9 m•kg, 50 ft•lb)
69 Nm (6.9 m•kg, 50 ft•lb)
85 Nm (8.5 m•kg, 61 ft•lb)
60 Nm (6.0 m•kg, 43 ft•lb)
5 Nm (0.5 m•kg, 3.6 ft•lb)
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4-62
ENGCRANKCASE AND CRANKSHAFT
Extent of removal Order Part name Q’ty Remarks
CRANKCASE AND CRANKSHAFT
REMOVAL
Preparation for Engine Refer to “ENGINE REMOVAL”section.
removal Piston Refer to “
CYLINDER HEAD, CYLINDER
AND PISTON
” section.
Primary drive gear
Kick idle gearRefer to “
KICK AXLE, SHIFT SHAFT AND
Stopper leverPRIMARY DRIVE GEAR”section.
Rotor and stator Refer to “CDI MAGNETO” section.
1 Segment 1 Refer to “REMOVAL POINTS”.
2 Bolt [L=50 mm (1.97 in)] 4
3 Bolt [L=60 mm (2.36 in)] 6
4 Bolt [L=70 mm (2.76 in)] 2
5 Holder 1
6 Crankcase (right) 1 Use special tool.
7 Crankcase (left) 1 Refer to “REMOVAL POINTS”.
8 Crankshaft 1 Use special tool.
Refer to “REMOVAL POINTS”.
9 Oil seal 2
10 Bearing 2 Refer to “REMOVAL POINTS”.





EC4N0000
12
3
Extent of removal:1Crankcase separation2Crankshaft removal
3Crankshaft bearing removal



30 Nm (3.0 m•kg, 22 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
20 Nm (2.0 m•kg, 14 ft•lb)
14 Nm (1.4 m•kg, 10 ft•lb)
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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)
5NY-9-30-4D 5/24/01 8:33 PM Page 24