2001 YAMAHA YZ125LC engine

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
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)
5MV-9-30-4D 6/19/00 1:39 PM Page 2

4-58
ENGENGINE REMOVAL
Extent of removal:1Engine removal
Extent of removal Order Part name Q’ty Remarks
1 Chain cover 1
2 Nut (drive sprocket) 1
3 Lock washer 1 Refer to “REMOVAL POINTS”.
4 Drive sprocket 1
5 Clip 1
6 Bolt (brake pedal) 1
7 Brake pedal 1
8 Engine bracket 2
9 Engine mounting bolt 3
10 Pivot shaft 1
Refer to “REMOVAL POINTS”.
11 Engine 1
1ü
ï
ý
ï
þ
ü
ý
þ
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)
5MV-9-30-4D 6/19/00 1:39 PM Page 4

4-59
ENGENGINE REMOVAL
EC4M3000
REMOVAL POINTS
EC4F3100
Drive sprocket
1. Remove:
9Nut (drive sprocket) 1
9Lock washer 2
NOTE:
9Straighten the lock washer tab.
9Loosen the nut while applying the rear brake.
2. Remove:
9Drive sprocket 1
9Drive chain 2
NOTE:
Remove the drive sprocket together with the dri-
ve chain.
EC4M3301
Engine removal
1. Remove:
9Pivot shaft 1
NOTE:
If the pivot shaft is pulled all the way out, the
swingarm will come loose. If possible, insert a
shaft of similar diameter into the other side of
the swingarm to support it.
2. Remove:
9Engine 1
From right side.
NOTE:
Make sure that the couplers, hoses and cables
are disconnected.
5MV-9-30-4D 6/19/00 1:39 PM Page 6

4-60
ENGENGINE REMOVAL
EC4M5000
ASSEMBLY AND INSTALLATION
EC4M5171
Engine installation
1. Install:
9Engine 1
Install the engine from right side.
9Pivot shaft 2
9Engine mounting bolt (lower) 3
9Engine mounting bolt (front) 4
9Engine bracket 5
9Bolt (engine bracket) 6
9CDI unit bracket 7
9Engine mounting bolt (upper) 8
NOTE:
Apply the molybdenum disulfide grease on the
pivot shaft.
EC4M5211
Brake pedal
1. Install:
9Spring 1
9Brake pedal 2
9O-ring 3
9Bolt (brake pedal) 4
9Clip 5
NOTE:
9Apply the lithium soap base grease on the bolt,
O-rings and brake pedal bracket.
9Install the clip with its stopper portion afacing
inward.
EC4M5311
Drive sprocket
1. Install:
9Drive sprocket 1
9Drive chain 2
NOTE:
Install the drive sprocket together with the drive
chain.
85 Nm (8.5 m•kg, 61 ft•lb)
69 Nm (6.9 m•kg, 50 ft•lb)
69 Nm (6.9 m•kg, 50 ft•lb)
34 Nm (3.4 m•kg, 24 ft•lb)
34 Nm (3.4 m•kg, 24 ft•lb)
26 Nm (2.6 m•kg, 19 ft•lb)
5MV-9-30-4D 6/19/00 1:39 PM Page 8

4-61
ENGENGINE REMOVAL
2. Install:
9Lock washer 1
9Nut (drive sprocket) 2
NOTE:
Tighten the nut while applying the rear brake.
3. Bend the lock washer tab to lock the nut.
4. Install:
9Chain cover 1
9Screw (chain cover) 2
5 Nm (0.5 m•kg, 3.6 ft•lb)
60 Nm (6.0 m•kg, 43 ft•lb)
5MV-9-30-4D 6/19/00 1:39 PM Page 10

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”.
ü
ï
ý
ï
þ
EC4N0000
12
3
Extent of removal:1Crankcase separation2Crankshaft removal
3Crankshaft bearing removal
ü
ý
þ
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)
5MV-9-30-4D 6/19/00 1:39 PM Page 12

4-63
ENGCRANKCASE AND CRANKSHAFT
EC4N3000
REMOVAL POINTS
EC4N3100
Segment
1. Remove:
9Bolt (segment) 1
9Segment 2
NOTE:
Turn the segment counterclockwise until it stops
and loosen the bolt.
EC4N3211
Crankcase
1. Remove:
9Crankcase (right) 1
Use the crankcase separating tool 2and
crankcase separating bolt 3.
NOTE:
9Fully tighten the tool holding bolts, but make
sure the tool body is parallel with the case. If
necessary, one screw may be backed out
slightly to level tool body.
9As pressure is applied, alternately tap on the
front engine mounting boss and transmission
shafts.
cC
Use soft hammer to tap on the case half.
Tap only on reinforced portions of case. Do
not tap on gasket mating surface. Work
slowly and carefully. Make sure the case
halves separate evenly. If one end “hangs
up”, take pressure off the push screw, re-
align, and start over. If the cases do not
separate, check for a remaining case
screw or fitting. Do not force.
Crankcase separating tool:
YU-1135-A/90890-01135
Crankcase separating bolt:
YM-1305/90890-01305
5MV-9-30-4D 6/19/00 1:39 PM Page 14

4-64
ENGCRANKCASE AND CRANKSHAFT
EC4N3301
Crankshaft
1. Remove:
9Crankshaft 1
Use the crankcase separating tool 2and
crankcase separating bolt 3.
cC
Do not use a hammer to drive out the
crankshaft.
EC4N3401
Crankshaft bearing
1. Remove:
9Bearing 1
NOTE:
9Remove the bearing from the crankcase by
pressing its inner race as shown in Œ.
9If the bearing is removed together with the
crankshaft, remove the bearing using a general
bearing puller 2as shown in º.
9Do not use the removed bearing.
EC4N4000
INSPECTION
EC4N4101
Crankcase
1. Inspect:
9Contacting surface a
Scratches ÕReplace.
9Engine mounting boss b, crankcase
Cracks/Damage ÕReplace.
Crankcase separating tool:
YU-1135-A/90890-01135
Crankcase separating bolt:
YM-1305/90890-01305
5MV-9-30-4D 6/19/00 1:39 PM Page 16