2012 YAMAHA YZ125LC engine

4-39
CRANKCASE AND CRANKSHAFT
CRANKCASE AND CRANKSHAFT
REMOVING THE CRANKSHAFT
Order Part name Q'ty Remarks
Engine Refer to "ENGINE REMOVAL" section.
PistonRefer to "CYLINDER HEAD, CYLINDER
AND PISTON" section.
Primary drive gearRefer to "KICK SHAFT AND SHIFT SHAFT"
section.
Kick idle gearRefer to "KICK SHAFT AND SHIFT SHAFT"
section.
Stopper leverRefer to "KICK SHAFT AND SHIFT SHAFT"
section.
Rotor and stator Refer to "CDI MAGNETO" section.
1 Segment 1 Refer to removal section.
2 Bolt [L=45 mm (1.77 in)] 6
3 Bolt [L=55 mm (2.17 in)] 4
4 Bolt [L=65 mm (2.56 in)] 1
5 Bolt [L=75 mm (2.95 in)] 1
6 Holder 1
7 Crankcase (right) 1 Refer to removal section.
8 Crankcase (left) 1 Refer to removal section.
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)

4-41
CRANKCASE AND CRANKSHAFT
REMOVING THE SEGMENT
1. Remove:
• Bolt (segment) "1"
• Segment "2"
Turn the segment counterclockwise
until it stops and loosen the bolt.
If the segment gets an impact, it
may be damaged. Take care not to
give an impact to the segment
when removing the bolt.
DISASSEMBLING THE
CRANKCASE
1. Remove:
• Crankcase (right) "1"
Use the flywheel puller "2".
• Make appropriate bolts "3" as
shown available by yourself and at-
tach the tool with them.
• Fully tighten the tool holding bolts,
but make sure the tool body is par-
allel with the case. If necessary,
one screw may be backed out
slightly to level tool body.
• As pressure is applied, alternately
tap on the engine mounting boss
and transmission shafts.
Use soft hammer to tap on the
case half. Tap only on reinforced
portions of case. Do not tap on
gasket mating surface. Work slow-
ly and carefully. Make sure the
case halves separate evenly. If one
end "hangs up", take pressure off
the push screw, realign, and start
over. If the cases do not separate,
check for a remaining case bolt or
fitting. Do not force.
REMOVING THE CRANKSHAFT
1. Remove:
• Crankshaft "1"
Use the crankcase separating
tool "2".
Make appropriate bolts "3" as shown
available by yourself and attach the
tool with them.
Do not use a hammer to drive out
the crankshaft.
REMOVING THE CRANKCASE
BEARING
1. Remove:
•Bearing "1"
• Remove the bearing from the
crankcase by pressing its inner race
as shown in "A".
• If the bearing is removed together
with the crankshaft, remove the
bearing using a general bearing
puller "2" as shown in "B".
• Do not use the removed bearing.
CHECKING THE CRANKCASE
1. Inspect:
• Contacting surface "a"
Scratches→Replace.
• Engine mounting boss "b", crank-
case
Cracks/damage→Replace.
2. Inspect:
• Bearing "1"
Rotate inner race with a finger.
Rough spot/seizure→Replace.
3. Inspect:
• Oil seal "1"
Damage→Replace.
CHECKING THE CRANKSHAFT
1. Measure:
• Runout limit "a"
• Small end free play limit "b"
• Connecting rod big end side
clearance "c"
• Crank width "d"
Out of specification→Replace.
Use the dial gauge and a thick-
ness gauge. Flywheel puller:
YU-1362-A/90890-
01362
Crankcase separating
tool:
YU-1135-A/90890-
01135
Dial gauge and stand:
YU-3097/90890-01252

4-43
CRANKCASE AND CRANKSHAFT
• Apply molybdenum disulfide grease
to the surface "a" where the crank-
shaft and bearing come in contact.
• Use two plain washers (Yamaha
genuine: 90201-243K3) "5" or the
ones of a size as shown one on the
other. (Except for USA and CDN)
• Install so that the plain washers do
not deviate from the crankshaft cen-
ter. (Except for USA and CDN)
• When installing the crankcase, the
connecting rod should be posi-
tioned at TDC (top dead center).
• Install while checking that the dowel
pin is in place.
A. For USA and CDN
B. Except for USA and CDN
6. Install:
• Clamp "1"
• Bolt (crankcase) "2"
Tighten the crankcase tightening
bolts in stage, using a crisscross pat-
tern.
7. Install:
• Holder "1"
• Bolt (holder) "2"
8. Install:
• Segment "1"
• Bolt (segment) "2"
• When installing the segment onto
the shift cam "3", align the punch
mark "a" with the dowel pin "b".
• Turn the segment clockwise until it
stops and tighten the bolt.
If the segment gets an impact, it
may be damaged. Take care not to
give an impact to the segment
when tightening the bolt.
9. Remove:
• Sealant
Forced out on the cylinder mating
surface.
10. Apply:
• Engine oil
To the crank pin, bearing, oil de-
livery hole and connecting rod big
end washer.11. Check:
• Crankshaft and transmission op-
eration.
Unsmooth operation→Repair.
If the crankshaft will not turn smooth-
ly, make an adjustment by gently tap-
ping its right end with a soft hammer.
Bolt (crankcase):
14 Nm (1.4 m•kg, 10
ft•lb)
(1.771.97 in)
(0.98
1.50 in)
(0.16
0.20 in)
Bolt (holder):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (segment):
30 Nm (3.0 m•kg, 22
ft•lb)

4-44
TRANSMISSION, SHIFT CAM AND SHIFT FORK
TRANSMISSION, SHIFT CAM AND SHIFT FORK
REMOVING THE TRANSMISSION, SHIFT CAM AND SHIFT FORK
Order Part name Q'ty Remarks
Engine Refer to "ENGINE REMOVAL" section.
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 Refer to removal section.
8 Drive axle 1 Refer to removal section.
9 Collar 1
10 Nm (1.0 m kg, 7.2 ft lb)
10 Nm (1.0 m kg, 7.2 ft lb)

5-1
FRONT WHEEL AND REAR WHEEL
CHASSIS
This section is intended for those who have basic knowledge and skill concerning the servicing of Yamaha motorcycles
(e.g., Yamaha dealers, service engineers, etc.) Those who have little knowledge and skill concerning servicing are request-
ed not to undertake inspection, adjustment, disassembly, or reassembly only by reference to this manual. It may lead to
servicing trouble and mechanical damage.
FRONT WHEEL AND REAR WHEEL
REMOVING THE FRONT WHEEL
Order Part name Q'ty Remarks
Hold the machine by placing the suitable stand
under the engine.Refer to "HANDLING NOTE".
1 Bolt (axle holder) 4 Only loosening.
2 Nut (front wheel axle) 1
3 Front wheel axle 1
4 Front wheel 1
5 Collar 2
6 Oil seal 2
7 Bearing 2 Refer to removal section.
8 Brake disc 1
5

5-2
FRONT WHEEL AND REAR WHEEL
REMOVING THE REAR WHEEL
Order Part name Q'ty Remarks
Hold the machine by placing the suitable stand
under the engine.Refer to "HANDLING NOTE".
1 Nut (rear wheel axle) 1
2 Rear wheel axle 1
3 Drive chain puller 2
4 Rear wheel 1 Refer to removal section.
5 Collar 2
6 Rear wheel sprocket 1
7 Oil seal 2
8 Circlip 1
9 Bearing 2 Refer to removal section.
10 Brake disc 1

5-6
FRONT BRAKE AND REAR BRAKE
FRONT BRAKE AND REAR BRAKE
REMOVING THE FRONT BRAKE
Order Part name Q'ty Remarks
Hold the machine by placing the suitable stand
under the engine.Refer to "HANDLING NOTE".
Drain the brake fluid. Refer to removal section.
1 Brake hose holder (protector) 2
2 Union bolt 2
3 Brake hose 1
4 Pad pin plug 1 Remove when loosening the pad pin.
5Pad pin 1Loosen when disassembling the brake cali-
per.
6 Brake caliper 1
7Brake lever 1
8 Brake master cylinder bracket 1
9 Brake master cylinder 1

5-7
FRONT BRAKE AND REAR BRAKE
REMOVING THE REAR BRAKE
Order Part name Q'ty Remarks
Hold the machine by placing the suitable stand
under the engine.Refer to "HANDLING NOTE".
Rear wheel Refer to "FRONT WHEEL AND REAR
WHEEL" section.
Drain the brake fluid. Refer to removal section.
1 Brake pedal 1
2 Brake master cylinder 1
3 Brake hose holder 2
4 Union bolt 2
5 Brake hose 1
6 Pad pin plug 1 Remove when loosening the pad pin.
7Pad pin 1Loosen when disassembling the brake cali-
per.
8 Brake caliper 1