2012 YAMAHA YZ125LC lock

3-7
ENGINE
3. Radiator cap
2. Apply the specified pressure.
3. Inspect:
• Pressure
Impossible to maintain the speci-
fied pressure for 10 seconds→
Replace.
CHECKING THE COOLING
SYSTEM
1. Inspect:
• Coolant level
2. Attach:
• Radiator cap tester "1" and adapt-
er "2"
3. Apply the specified pressure.
• Do not apply pressure more than
specified pressure.
• Radiator should be filled fully.
4. Inspect:
• Pressure
Impossible to maintain the speci-
fied pressure for 10 seconds→
Repair.
•Radiator "1"
• Radiator hose joint "2"
Coolant leakage→Repair or re-
place.
• Radiator hose "3"
Swelling→Replace.ADJUSTING THE CLUTCH CABLE
FREE PLAY
1. Check:
• Clutch lever free play "a"
Out of specification→Adjust.
2. Adjust:
• Clutch lever free play
Clutch lever free play adjustment
steps:
a. Loosen the locknuts "1".
b. Turn the adjuster "2" until free
play "a" is within the specified lim-
its.
c. Tighten the locknuts.
• Before adjustment, expose the ad-
juster by moving the boot "3" and
cap "4" away.
• Make minute adjustment on the le-
ver side using the adjuster "5".
• After adjustment, check proper op-
eration of clutch lever.
3. Install:
• Cap "1"
•Boot "2"
Place the tip "a" of the cap in the boot.
ADJUSTING THE THROTTLE GRIP
FREE PLAY
1. Check:
• Throttle grip free play "a"
Out of specification→Adjust.
2. Adjust:
• Throttle grip free play
Adjustment steps:
a. Slide the adjuster cover.
b. Loosen the locknut "1".
c. Turn the adjuster "2" until the
specified free play is obtained.
d. Tighten the locknut.
Prior to adjusting throttle grip free
play, the engine idling speed should
be adjusted.
After adjusting the throttle grip
free play, turn the handlebar to the
right and to the left to ensure that
this does not cause the engine
idling speed to change.
Radiator cap opening
pressure:
95–125 kPa (0.95–1.25
kg/cm
2, 13.5–17.8 psi)
Radiator cap tester:
YU-24460-01/90890-
01325
Radiator cap tester
adapter:
YU-33984/90890-01352
Standard pressure:
180 kPa (1.8 kg/cm
2,
25.6 psi)
Clutch lever free play "a"
:
8–13 mm (0.31–0.51 in)
Locknut:
4 Nm (0.4 m•kg, 2.9
ft•lb)Throttle grip free play
"a":
3–5 mm (0.12–0.20 in)
Locknut:
7 Nm (0.7 m•kg, 5.1
ft•lb)

3-9
CHASSIS
c. Inspect the gasket (oil check bolt),
replace if damaged.
d. Tighten the oil check bolt.
CHANGING THE TRANSMISSION
OIL
1. Start the engine and warm it up
for several minutes and wait for
five minute.
2. Place the machine on a level
place and hold it on upright posi-
tion by placing the suitable stand
under the engine.
3. Place a suitable container under
the engine.
4. Remove:
• Oil drain bolt "1"
• Oil filler cap "2"
Drain the transmission oil.
5. Install:
• Aluminum washer
• Oil drain bolt "1"6. Fill:
• Transmission oil
7. Check:
• Oil leakage
8. Check:
• Transmission oil level
9. Install:
• Oil filler cap "2"
ADJUSTING THE PILOT SCREW
1. Adjust:
• Pilot air screw "1"
Adjustment steps:
a. Screw in the pilot air screw until it
is lightly seated.
b. Back out by the specified number
of turns.
ADJUSTING THE ENGINE IDLING
SPEED
1. Start the engine and thoroughly
warm it up.
2. Adjust:
• Engine idling speed
Adjustment steps:
a. Loosen the locknut "1".
b. Turn the throttle stop screw "2"
until the engine runs at the lowest
possible speed.
c. Tighten the locknut.
CHECKING THE EXHAUST PIPE
1. Inspect:
• O-ring "1"
Damage→Replace.
Install the O-rings with their de-
pressed "a" facing outward.
CHASSIS
BLEEDING THE HYDRAULIC
BRAKE SYSTEM
Bleed the brake system if:
• The system has been disassem-
bled.
• A brake hose has been loosened
or removed.
• The brake fluid is very low.
• The brake operation is faulty.
A dangerous loss of braking per-
formance may occur if the brake
system is not properly bled.
1. Remove:
• Brake master cylinder cap
• Diaphragm
• Reservoir float (front brake)
• Protector (rear brake)
2. Bleed:
• Brake fluid
Air bleeding steps:
a. Add proper brake fluid to the res-
ervoir.
b. Install the diaphragm. Be careful
not to spill any fluid or allow the
reservoir to overflow.
c. Connect the clear plastic tube "2"
tightly to the caliper bleed screw
"1". Oil check bolt:
10 Nm (1.0 m•kg, 7.2
ft•lb)
Oil drain bolt:
20 Nm (2.0 m•kg, 14
ft•lb)
Recommended brand:
YAMALUBE
Recommended engine
oil type
SAE10W-40
Recommended engine
oil grade
API service SG type or
higher
JASO standard MA
Oil capacity (periodic oil
change):
0.66 L (0.58 Imp qt, 0.69
US qt)
Pilot air screw:
2-1/4 turns out
To increase idle speed→Turn the
throttle stop screw "2" in.
To decrease idle speed→Turn the
throttle stop screw "2" out.

3-10
CHASSIS
A. Front
B. Rear
d. Place the other end of the tube
into a container.
e. Slowly apply the brake lever or
pedal several times.
f. Pull the lever in or push down on
the pedal. Hold the lever or pedal
in position.
g. Loosen the bleed screw and allow
the lever or pedal to travel to-
wards its limit.
h. Tighten the bleed screw when the
lever or pedal limit has been
reached; then release the lever or
pedal.
i. Repeat steps (e) to (h) until of the
air bubbles have been removed
from the system.
If bleeding is difficult, it may be nec-
essary to let the brake fluid system
stabilize for a few hours. Repeat the
bleeding procedure when the tiny
bubbles in the system have disap-
peared.
j. Add brake fluid to the level line on
the reservoir.
Check the operation of the brake
after bleeding the brake system.
3. Install:
• Protector (rear brake)
• Reservoir float (front brake)
• Diaphragm
• Brake master cylinder capADJUSTING THE FRONT BRAKE
1. Check:
• Brake lever position "a"
2. Remove:
• Brake lever cover
3. Adjust:
• Brake lever position
Brake lever position adjustment
steps:
a. Loosen the locknut "1".
b. Turn the adjusting bolt "2" until the
lever position "a" is within speci-
fied position.
c. Tighten the locknut.
Be sure to tighten the locknut, as it
will cause poor brake perfor-
mance.
4. Install:
• Brake lever cover
ADJUSTING THE REAR BRAKE
1. Check:
• Brake pedal height "a"
Out of specification→Adjust.2. Adjust:
• Brake pedal height
Pedal height adjustment steps:
a. Loosen the locknut "1".
b. Turn the adjusting nut "2" until the
pedal height "a" is within specified
height.
c. Tighten the locknut.
• Adjust the pedal height between
the maximum "A" and the mini-
mum "B" as shown. (In this ad-
justment, the bolt "3" end "b"
should protrude out of the
threaded portion "4" but not be
less than 2 mm (0.08 in) "c" away
from the brake pedal "5").
• After the pedal height adjust-
ment, make sure that the rear
brake does not drag.
CHECKING AND REPLACING THE
FRONT BRAKE PADS
1. Inspect:
• Brake pad thickness "a"
Out of specification→Replace as
a set. Bleed screw:
6 Nm (0.6 m•kg, 4.3
ft•lb)
Brake lever position "a":
Standard posi-
tionExtent of ad-
justment
95 mm (3.74 in)86–105 mm
(3.39–4.13 in)
Locknut:
5 Nm (0.5 m •kg, 3.6
ft•lb)
Brake pedal height "a":
Zero mm (Zero in)
Brake pad thickness:
4.4 mm (0.17 in)
: 1.0 mm (0.04
in)

3-13
CHASSIS
2. Remove:
• Master link clip
•Joint "1"
• Drive chain "2"
3. Clean:
• Drive chain
Place it in kerosene, and brush off
as much dirt as possible. Then re-
move the drive chain from the ker-
osene and dry the drive chain.
4. Check:
• Drive chain stiffness "a"
Clean and oil the drive chain and
hold as illustrated.
Stiff→Replace the drive chain.
5. Install:
• Drive chain "1"
•Joint "2"
• Master link clip "3"
Be sure to install the master link
clip to the direction as shown.
a. Turning direction6. Lubricate:
• Drive chain
ADJUSTING THE DRIVE CHAIN
SLACK
1. Elevate the rear wheel by placing
the suitable stand under the en-
gine.
2. Check:
• Drive chain slack "a"
Above the seal guard installation
bolt.
Out of specification→Adjust.
Before checking and/or adjusting, ro-
tate the rear wheel through several
revolutions and check the slack sev-
eral times to find the tightest point.
Check and/or adjust the drive chain
slack with the rear wheel in this "tight
chain" position.
3. Adjust:
• Drive chain slack
Drive chain slack adjustment
steps:
a. Loosen the axle nut "1" and lock-
nuts "2".
b. Adjust the drive chain slack by
turning the adjusters "3".c. Turn each adjuster exactly the
same amount to maintain correct
axle alignment. (There are marks
"a" on each side of the drive chain
puller alignment.) NOTICE: Im-
proper drive chain slack will
overload the engine as well as
other vital parts of the motorcy-
cle and can lead to chain slip-
page or breakage. To prevent
this from occurring, keep the
drive chain slack within the
specified limits.
Turn the adjuster so that the drive
chain is in line with the sprocket, as
viewed from the rear.
d. Tighten the axle nut while pushing
down the drive chain.
e. Tighten the locknuts.
CHECKING THE FRONT FORK
1. Inspect:
• Front fork smooth action
Operate the front brake and
stroke the front fork.
Unsmooth action/oil leakage→
Repair or replace.
Drive chain lubricant:
SAE 10W-40 motor oil
or suitable chain lubri-
cants
Drive chain slack:
48–58 mm (1.9–2.3 in)
To tighten→Turn the adjuster "3"
counterclockwise.
To loosen→Turn the adjuster "3"
clockwise and push wheel for-
ward.
Axle nut:
125 Nm (12.5 m•kg, 90
ft•lb)
Locknut:
19 Nm (1.9 m•kg, 13
ft•lb)

3-15
CHASSIS
3. Measure:
• Spring fitting length
• The I.D. mark "a" is marked at the
end of the spring.
• Spring specification varies accord-
ing to the difference in the produc-
tion lot.
4. Adjust:
• Spring preload
Adjustment steps:
a. Loosen the locknut "1".
b. Loosen the adjuster "2" until there
is some clearance between the
spring and adjuster.
c. Measure the spring free length
"a".
d. Turn the adjuster "2".
• Be sure to remove all dirt and mud
from around the locknut and adjust-
er before adjustment.
• The length of the spring (installed)
changes 1.5 mm (0.06 in) per turn
of the adjuster.
Never attempt to turn the adjuster
beyond the maximum or minimum
setting.
e. Tighten the locknut.
5. Install:
• Rear frame (upper)
• Rear frame (lower)
ADJUSTING THE REAR SHOCK
ABSORBER REBOUND DAMPING
FORCE
1. Adjust:
• Rebound damping force
By turning the adjuster "1".• STANDARD POSITION:
This is the position which is back
by the specific number of clicks
from the fully turned-in position.
(Which align the punch mark "a"
on the adjuster with the punch
mark "b" on the bracket.)
Do not force the adjuster past the
minimum or maximum extent of
adjustment. The adjuster may be
damaged.
ADJUSTING THE REAR SHOCK
ABSORBER LOW COMPRESSION
DAMPING FORCE
1. Adjust:
• Low compression damping force
By turning the adjuster "1". Standard fitting length:
I.D. MARK/
Q'TYLength
Red/1
Red/2
Red/3258 mm
(10.16 in)
*252 mm
(9.92 in)
264 mm
(10.39 in)
*258 mm
(10.16 in)
255.5 mm
(10.06 in)
*249.5 mm
(9.82 in)
*For EUROPE
Stiffer →Increase the spring pre-
load. (Turn the adjuster "2" in.)
Softer→Decrease the spring pre-
load. (Turn the adjuster "2"
out.)
Extent of adjustment:
Maximum Minimum
Position in
which the
spring is turned
in 18 mm (0.71
in) from its free
length.Position in
which the
spring is turned
in 1.5 mm (0.06
in) from its free
length.
Locknut:
30 Nm (3.0 m•kg, 22
ft•lb)
Rear frame (upper):
32 Nm (3.2 m•kg, 23
ft•lb)
Rear frame (lower):
29 Nm (2.9 m•kg, 21
ft•lb)
Stiffer "a" →Increase the re-
bound damping force. (Turn
the adjuster "1" in.)
Softer "b" →Decrease the re-
bound damping force. (Turn
the adjuster "1" out.)
Extent of adjustment:
Maximum Minimum
Fully turned in
position20 clicks out
(from maximum
position)
Standard position:
10–13 clicks out
* 11–14 clicks out
* For EUROPE
Stiffer "a" →Increase the low
compression damping force.
(Turn the adjuster "1" in.)
Softer "b" →Decrease the low
compression damping force.
(Turn the adjuster "1" out.)
Extent of adjustment:
Maximum Minimum
Fully turned in
position20 clicks out
(from maximum
position)

3-17
CHASSIS
CHECKING AND ADJUSTING THE
STEERING HEAD
1. Place a stand under the engine to
raise the front wheel off the
ground. WARNING! Securely
support the vehicle so that
there is no danger of it falling
over.
2. Check:
• Steering stem
Grasp the bottom of the forks and
gently rock the fork assembly
back and forth.
Free play→Adjust steering head.
3. Check:
• Steering smooth action
Turn the handlebar lock to lock.
Unsmooth action→Adjust steer-
ing ring nut.
4. Adjust:
• Steering ring nut
Steering ring nut adjustment
steps:
a. Remove the number plate.
b. Remove the handlebar and upper
bracket.
c. Loosen the steering ring nut "1"
using the steering nut wrench "2".
d. Tighten the steering ring nut "3"
using steering nut wrench "4".
• Apply the lithium soap base grease
on the thread of the steering stem.
• Set the torque wrench to the steer-
ing nut wrench so that they form a
right angle.
e. Loosen the steering ring nut one
turn.
f. Retighten the steering ring nut us-
ing the steering nut wrench.
Avoid over-tightening.
g. Check the steering stem by turn-
ing it lock to lock. If there is any
binding, remove the steering stem
assembly and inspect the steer-
ing bearings.
h. Install the washer "5", upper
bracket "6", washer "7", steering
stem nut "8", handlebar "9", han-
dlebar upper holder "10" and
number plate "11".
• The handlebar upper holder should
be installed with the punched mark
"a" forward.
• Install the handlebar so that the
marks "b" are in place on both
sides.
• Install the handlebar so that the pro-
jection "c" of the handlebar upper
holder is positioned at the mark on
the handlebar as shown.
• Insert the end of the fuel breather
hose "12" into the hole in the steer-
ing stem.
First tighten the bolts on the front
side of the handlebar upper holder,
and then tighten the bolts on the
rear side.
Steering nut wrench:
YU-33975/90890-01403
Steering nut wrench:
YU-33975/90890-01403
Steering ring nut (initial
tightening):
38 Nm (3.8 m•kg, 27
ft•lb)
Steering ring nut (final
tightening):
7 Nm (0.7 m•kg, 5.1
ft•lb)Steering stem nut:
145 Nm (14.5 m•kg, 105
ft•lb)
Handlebar upper holder:
28 Nm (2.8 m•kg, 20
ft•lb)
Pinch bolt (upper brack-
et):
21 Nm (2.1 m•kg, 15
ft•lb)
Number plate:
7 Nm (0.7 m•kg, 5.1
ft•lb)

3-19
ELECTRICAL
ELECTRICAL
CHECKING THE SPARK PLUG
1. Remove:
• Spark plug
2. Inspect:
• Electrode "1"
Wear/damage→Replace.
• Insulator color "2"
Normal condition is a medium to
light tan color.
Distinctly different color→Check
the engine condition.
When the engine runs for many hours
at low speeds, the spark plug insula-
tor will become sooty, even if the en-
gine and carburetor are in good
operating condition.
3. Measure:
• Plug gap "a"
Use a wire gauge or thickness
gauge.
Out of specification→Regap.
4. Clean the plug with a spark plug
cleaner if necessary.
5. Tighten:
• Spark plug
• Before installing a spark plug, clean
the gasket surface and plug sur-
face.
• Finger-tighten "a" the spark plug
before torquing to specification "b".
CHECKING THE IGNITION TIMING
1. Remove:
•Fuel tank
Refer to "SEAT, FUEL TANK
AND SIDE COVERS" section in
the CHAPTER 4.
• Spark plug
• Crankcase cover (left)
2. Attach:
• Dial gauge "1"
• Spark plug hole dial stand "2"
3. Rotate the magneto rotor "1" until
the piston reaches top dead cen-
ter (TDC). When this happens,
the needle on the dial gauge will
stop and reverse directions even
though the rotor is being turned in
the same direction.
4. Set the dial gauge to zero at TDC.
5. From TDC, rotate the rotor clock-
wise until the dial gauge indicates
that the piston is at a specified
distance from TDC.
6. Check:
• Ignition timing
Punch mark "a" on rotor should be
aligned with punch mark "b" on
stator.
Not aligned→Adjust.7. Adjust:
• Ignition timing
Adjustment steps:
a. Loosen the screws (stator) "1".
b. Align the punch mark on the rotor
with punch mark on the stator "2"
by moving the stator.
c. Tighten the screws (stator).
Spark plug gap:
0.6–0.7 mm (0.024–
0.028 in)
Standard spark plug:
BR9EVX/NGK (resistance type)
Spark plug:
20 Nm (2.0 m•kg, 14
ft•lb)
Dial gauge:
YU-3097/90890-01252
Spark plug hole dial
stand:
YU-1256
Ignition timing (B.T.D.C.):
0.48 mm (0.019 in)
Screw (stator):
7 Nm (0.7 m•kg, 5.1
ft•lb)

4-6
RADIATOR
HANDLING NOTE
Do not remove the radiator cap
when the engine and radiator are
hot. Scalding hot fluid and steam
may be blown out under pressure,
which could cause serious injury.
When the engine has cooled, open
the radiator cap by the following
procedure:
Place a thick rag, like a towel, over
the radiator cap, slowly rotate the
cap counterclockwise to the de-
tent. This procedure allows any re-
sidual pressure to escape. When
the hissing sound has stopped,
press down on the cap while turn-
ing counterclockwise and remove
it.
CHECKING THE RADIATOR
1. Inspect:
• Radiator core "1"
Obstruction→Blow out with com-
pressed air through rear of the ra-
diator.
Bent fin→Repair/replace.
INSTALLING THE RADIATOR
1. Install:
• Radiator breather hose "1"
• Radiator hose 3 "2"
• Radiator hose 1 "3"
To right radiator "4".
Clamp the radiator hose in the direc-
tion as shown.
2. Install:
• Right radiator "1"
• Washer "2"
• Bolt (right radiator) "3"
• Radiator hose 4 "4"
Refer to "CABLE ROUTING DIA-
GRAM" section in the CHAPTER
2.
3. Install:
• Left radiator "1"
• Washer "2"
• Bolt (left radiator) "3"
• Radiator hose 2 "4"
Refer to "CABLE ROUTING DIA-
GRAM" section in the CHAPTER
2.
4. Tighten:
• Radiator hose clamp 1, 3 "5"
5. Install:
• Radiator guard "1"
• Bolt (radiator guard) "2"
Fit the hook "a" on the inner side first
into the radiator.
Radiator hose 3:
2 Nm (0.2 m•kg, 1.4
ft•lb)
Radiator hose 1:
2 Nm (0.2 m•kg, 1.4
ft•lb)
Bolt (right radiator):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Radiator hose 4:
2 Nm (0.2 m•kg, 1.4
ft•lb)
Bolt (left radiator):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Radiator hose 2:
2 Nm (0.2 m•kg, 1.4
ft•lb)
Radiator hose clamp 1, 3:
2 Nm (0.2 m•kg, 1.4
ft•lb)
Bolt (radiator guard):
10 Nm (1.0 m•kg, 7.2
ft•lb)