2012 YAMAHA YZ125LC seat adjustment

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.

3-19
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)

4-1
SEAT, FUEL TANK AND SIDE COVERS
ENGINE
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.
SEAT, FUEL TANK AND SIDE COVERS
REMOVING THE SEAT, FUEL TANK AND SIDE COVERS
Order Part name Q'ty Remarks
Turn the fuel cock to "OFF".
Disconnect the fuel hose.
1Seat 1
2 Air scoop (left and right) 2
3 Fitting band 1 Remove on fuel tank side.
4 Bolt (fuel tank) 2
5 Fuel tank 1
6 Left side cover 1 Refer to removal section.
7 Right side cover 1 Refer to removal section.
8 Number plate 1 Refer to removal section.
19 Nm (1.9 m kg, 13 ft lb)
7 Nm (0.7 m kg, 5.1 ft lb)
7 Nm (0.7 m kg, 5.1 ft lb)
7 Nm (0.7 m kg, 5.1 ft lb)
7 Nm (0.7 m kg, 5.1 ft lb)
7 Nm (0.7 m kg, 5.1 ft lb)
7 Nm (0.7 m kg, 5.1 ft lb)
7 Nm (0.7 m kg, 5.1 ft lb)
19 Nm (1.9 m kg, 13 ft lb)
6 Nm (0.6 m kg, 4.3 ft lb)
6 Nm (0.6 m kg, 4.3 ft lb)
10 Nm (1.0 m kg, 7.2 ft lb)
4 Nm (0.4 m kg, 2.9 ft lb)
4

7-7
CHASSIS
Adjust the oil amount in 5 cm3 (0.2
Imp oz, 0.2 US oz) increments or
decrements. Too small oil amount
causes the front fork to produce a
noise at full rebound or the rider to
feel some pressure on his hands
or body. Alternatively, too large oil
amount will cause the air spring
characteristics to have a tendency
to be stiffer with the consequent
deteriorated performance and
characteristics. Therefore, adjust
the front fork within the specified
range.
A. Air spring characteristics in
relation to oil amount change
B. Load
C. Stroke
1. Max. oil amount
2. Standard oil amount
3. Min. oil amount
SETTING OF SPRING AFTER
REPLACEMENT
As the front fork setting can be easily
affected by rear suspension, take
care so that the machine front and
rear are balanced (in position, etc.)
when setting the front fork.
1. Use of soft spring
• Change the rebound damping.
Turn out one or two clicks.
• Change the compression damp-
ing.
Turn in one or two clicks.
Generally a soft spring gives a soft
riding feeling. Rebound damping
tends to become stronger and the
front fork may sink deeply over a se-
ries of gaps.
2. Use of stiff spring
• Change the rebound damping.
Turn in one or two clicks.
• Change the compression damp-
ing.
Turn out one or two clicks.
Generally a stiff spring gives a stiff
riding feeling. Rebound damping
tends to become weaker, resulting in
lack of a sense of contact with the
road surface or in a vibrating handle-
bar.
FRONT FORK SETTING PARTS
• Front fork spring "1"
The I.D. mark (slits) "a" is proved on
the end of the spring.
REAR SUSPENSION SETTING
The rear suspension setting should
be made depending on the rider's
feeling of an actual run and the circuit
conditions.
The rear suspension setting includes
the following two factors:
1. Setting of spring preload
• Change the set length of the
spring.
• Change the spring.
2. Setting of damping force
• Change the rebound damping.
• Change the compression damp-
ing.
CHOOSING SET LENGTH
1. Place a stand or block under the
engine to put the rear wheel
above the floor, and measure the
length "a" between the rear wheel
axle center and the rear fender
holding bolt.
2. Remove the stand or block from
the engine and with a rider astride
the seat, measure the sunken
length "b" between the rear wheel
axle center and the rear fender
holding bolt.
3. Loosen the locknut "1" and make
adjustment by turning the spring
adjuster "2" to achieve the stan-
dard figure from the subtraction of
the length "b" from the length "a".
• If the machine is new and after it is
broken in, the same set length of
the spring may change because of
the initial fatigue, etc. of the spring.
Therefore, be sure to make reeval-
uation.
• If the standard figure cannot be
achieved by adjusting the spring
adjuster and changing the spring Standard oil amount:
333 cm
3 (11.72 Imp oz,
11.26 US oz)
*335 cm
3 (11.79 Imp oz,
11.33 US oz)
Extent of adjustment:
300–375 cm
3 (10.6–13.2
Imp oz, 10.1–12.7 US
oz)
* For EUROPE
TY
PESPRIN
G
RATESPRING
PART NUM-
BER (-23141-)I.D.
MA
RK
(slit
s)
SO
FT0.398 1C3-A1 |
0.408 1C3-B1 ||
ST
D0.418 1C3-P0 —
STI
FF0.428 1C3-D1 ||||
0.438 1C3-E1 |||||
0.449 1C3-F1 |-|
0.459 1C3-G1 |-||
0.469 1C3-H1 |-|||
0.479 1C3-J1 |-||||
Standard figure:
90–100 mm (3.5–3.9 in)

7-10
CHASSIS
SUSPENSION SETTING (FRONT FORK)
• If any of the following symptoms is experienced with the standard position as the base, make resetting by reference to
the adjustment procedure given in the same chart.
• Before any change, set the rear shock absorber sunken length to the standard figure 90–100 mm (3.5–3.9 in).
SymptomSection
Check Adjust
JumpLarge
gapMedi-
um
gapSmall
gap
Stiff over entire
range○○○Compression damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Oil amount Decrease oil amount by about 5–10 cm
3 (0.2–0.4
Imp oz, 0.2–0.3 US oz).
Spring Replace with soft spring.
Unsmooth move-
ment over entire
range○○○○Outer tube Check for any bends, dents, and other noticeable
scars, etc. If any, replace affected parts.
Inner tube
Slide metal Replace with a new one for extended use.
Piston metal Replace with a new one for extended use.
Under bracket tighten-
ing torqueRetighten to specified torque.
Poor initial move-
ment○Rebound damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Oil seal Apply grease in oil seal wall.
Soft over entire
range, bottoming
out○○Compression damping Turn adjuster clockwise (about 2 clicks) to in-
crease damping.
Oil amount Increase oil amount by about 5–10 cm
3 (0.2–0.4
Imp oz, 0.2–0.3 US oz).
Spring Replace with stiff spring.
Stiff toward stroke
end○Oil amountDecrease oil amount by about 5 cm
3 (0.2 Imp
oz,0.2 US oz).
Soft toward stroke
end, bottoming out○Oil amountIncrease oil amount by about 5 cm
3 (0.2 Imp
oz,0.2 US oz).
Stiff initial move-
ment○○○○Compression dampingTurn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Low front, tending to
lower front posture○○Compression damping Turn adjuster clockwise (about 2 clicks) to in-
crease damping.
Rebound damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Balance with rear end Set sunken length for 95–100 mm (3.7–3.9 in)
when one passenger is astride seat (lower rear
posture).
Oil amount Increase oil amount by about 5 cm
3 (0.2 Imp oz,
0.2 US oz).
"Obtrusive" front,
tending to upper
front posture○○Compression damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Balance with rear end Set sunken length for 90–95 mm (3.5–3.7 in)
when one passenger is astride seat (upper rear
posture).
Spring Replace with soft spring.
Oil amount Decrease oil amount by about 5–10 cm
3 (0.2–0.4
Imp oz, 0.2–0.3 US oz).

7-11
CHASSIS
SUSPENSION SETTING (REAR SHOCK ABSORBER)
• If any of the following symptoms is experienced with the standard position as the base, make resetting by reference to
the adjustment procedure given in the same chart.
• Adjust the rebound damping in 2-click increments or decrements.
• Adjust the low compression damping in 1-click increments or decrements.
• Adjust the high compression damping in 1/6 turn increments or decrements.
SymptomSection
Check Adjust
JumpLarge
gapMedi-
um
gapSmall
gap
Stiff, tending to sink○○Rebound damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Spring set length Set sunken length for 90–100 mm (3.5–3.9 in)
when one passenger is astride seat.
Spongy and unsta-
ble○○Rebound damping Turn adjuster clockwise (about 2 clicks) to in-
crease damping.
Low compression
dampingTurn adjuster clockwise (about 1 click) to increase
damping.
Spring Replace with stiff spring.
Heavy and dragging○○Rebound damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Spring Replace with soft spring.
Poor road gripping○Rebound damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Low compression
dampingTurn adjuster clockwise (about 1 clicks) to in-
crease damping.
High compression
dampingTurn adjuster clockwise (about 1/6 turn) to in-
crease damping.
Spring set length Set sunken length for 90–100 mm (3.5–3.9 in)
when one passenger is astride seat.
Spring Replace with soft spring.
Bottoming out○○High compression
dampingTurn adjuster clockwise (about 1/6 turn) to in-
crease damping.
Spring set length Set sunken length for 90–100 mm (3.5–3.9 in)
when one passenger is astride seat.
Spring Replace with stiff spring.
Bouncing○○Rebound damping Turn adjuster clockwise (about 2 clicks) to in-
crease damping.
Spring Replace with soft spring.
Stiff travel○○High compression
dampingTurn adjuster counterclockwise (about 1/6 turn) to
decrease damping.
Spring set length Set sunken length for 90–100 mm (3.5–3.9 in)
when one passenger is astride seat.
Spring Replace with soft spring.