2012 YAMAHA YZ125LC engine

2-13
CABLE ROUTING DIAGRAM
CABLE ROUTING DIAGRAM
1. "ENGINE STOP" button lead
2. Throttle cable
3. Clutch cable
4. Ground lead
5. High tension cord
6. Clamp
7. Air vent hose
8. Radiator breather hose
9. CDI magneto lead10. YPVS breather hose
11. Engine bracket (right)
12. Engine bracket (left)
13. Crankcase breather hose
14. Overflow hose
15. Connector cover
A. Pass the clutch cable on the out-
side of the throttle cable and
"ENGINE STOP" button lead.B. Align the throttle cable locating
tape with the cable guide.
C. Pass the throttle cable, clutch
cable and "ENGINE STOP" but-
ton lead above the radiator
hose.

2-14
CABLE ROUTING DIAGRAM
D. Install the ignition coil, side core
and ground lead together to the
frame. Take care to fasten the
ground lead so that its terminal
is within the indicated range.
E. Clamp the throttle cable and
high tension cord to the frame.
F. Clamp the clutch cable to the left
engine bracket. Clamp the
clutch cable below the position-
ing grommet.
G. Pass the air vent hose back of
the throttle cable.
H. Pass the air vent hose, overflow
hose and crankcase breather
hose between the frame and
connecting rod.
I. Pass the radiator breather hose
and YPVS breather hose out-
side the engine bracket and in-
side the down tube. Then pass
the radiator breather hose inside
the YPVS breather hose.
J. Clamp the CDI magneto lead,
radiator breather hose and
YPVS breather hose to the
frame.
K. Clamp to the frame the CDI
magneto lead and radiator
breather hose. Take care to
clamp them above the projection
on the frame.
L. Locate the clamp ends in the ar-
rowed range.
M. Direct the clip with its finger grip
facing forward.
N. Tighten the clamp with its bolt
head facing the left side of the
chassis (on both sides of the
carburetor joint and the air filter
joint).
O. Pass the air vent hose, overflow
hose and crankcase breather
hose so that they do not contact
the rear shock absorber.
P. Bring the connector cover into
contact with the coupler.

2-15
CABLE ROUTING DIAGRAM
1. High tension cord
2. "ENGINE STOP" button lead
3. Ignition coil lead
4. Clamp
5. CDI unit
6. CDI unit band
7. Radiator breather hose
8. CDI magneto lead
9. Connector cover
10. Throttle cable
11. Clutch cable12. CDI unit stay
A. Pass the high tension cord to the
left of the radiator hose.
B. Using a plastic locking tie, clamp
the "ENGINE STOP" button
lead, ignition coil lead and CDI
magneto lead together with the
clamp ends backward and then
cut off the tie end.C. Clamp to the frame the throttle
cable, clutch cable, ignition coil
lead and "ENGINE STOP" but-
ton lead. In so doing, clamp the
ignition coil lead and "ENGINE
STOP" button lead at their pro-
tecting tubes. Tighten the clamp
so that the "ENGINE STOP" but-
ton lead is not pulled when the
handlebar is turned to the right
and left.

2-18
CABLE ROUTING DIAGRAM
1. Brake hose
2. Master cylinder
3. "ENGINE STOP" button lead
4. "ENGINE STOP" button
5. Throttle cable
6. Clutch cable
7. Clamp
8. Cable guideA. Install the brake hose so that its
pipe portion directs as shown
and lightly touches the projec-
tion on the master cylinder.
B. Pass the "ENGINE STOP" but-
ton lead in the middle of the
clutch holder.
C. Clamp the "ENGINE STOP" but-
ton lead to the handlebar.D. Pass the brake hose in front of
the number plate and through
the cable guide.
E. Pass the clutch cable through
the cable guide on the number
plate.

3-5
PRE-OPERATION INSPECTION AND MAINTENANCE
PRE-OPERATION INSPECTION AND MAINTENANCE
Before riding for break-in operation, practice or a race, make sure the machine is in good operating condition.
Before using this machine, check the following points.
GENERAL INSPECTION AND MAINTENANCE
Item Routine Page
CoolantCheck that coolant is filled up to the radiator cap. Check the cool-
ing system for leakage.P. 3-6 – 7
FuelCheck that a fresh mixture of oil and gasoline is filled in the fuel
tank. Check the fuel line for leakage.P. 1-12
Transmission oilCheck that the oil level is correct. Check the crankcase for leak-
age.P. 3-8 – 9
Gear shifter and clutchCheck that gears can be shifted correctly in order and that the
clutch operates smoothly.P. 3-7
Throttle grip/HousingCheck that the throttle grip operation and free play are correctly
adjusted. Lubricate the throttle grip and housing, if necessary.P. 3-7 – 8
Brakes Check the play of front brake and effect of front and rear brake. P. 3-9 – 12
Drive chainCheck drive chain slack and alignment. Check that the drive chain
is lubricated properly.P. 3-12 – 13
WheelsCheck for excessive wear and tire pressure. Check for loose
spokes and have no excessive play.P. 3-16
SteeringCheck that the handlebar can be turned smoothly and have no ex-
cessive play.P. 3-17
Front forks and rear shock
absorberCheck that they operate smoothly and there is no oil leakage.
P. 3-13 – 16
Cables (wires)Check that the clutch and throttle cables move smoothly. Check
that they are not caught when the handlebars are turned or when
the front forks travel up and down.—
Muffler Check that the muffler is tightly mounted and has no cracks. P. 4-3 – 4
Rear wheel sprocket Check that the rear wheel sprocket tightening bolt is not loose. P. 3-12
Lubrication Check for smooth operation. Lubricate if necessary. P. 3-18
Bolts and nuts Check the chassis and engine for loose bolts and nuts. P. 1-13
Lead connectorsCheck that the CDI magneto, CDI unit, and ignition coil are con-
nected tightly.P. 1-7
SettingsIs the machine set suitably for the condition of the racing course
and weather or by taking into account the results of test runs be-
fore racing? Are inspection and maintenance completely done?P. 7-1 – 11

3-6
ENGINE
ENGINE
CHECKING THE COOLANT LEVEL
Do not remove the radiator cap
"1", drain bolt and hoses when the
engine and radiator are hot. Scald-
ing hot fluid and steam may be
blown out under pressure, which
could cause serious injury. When
the engine has cooled, place a
thick towel over the radiator cap,
slowly rotate the cap counter-
clockwise to the detent. This pro-
cedure allows any residual
pressure to escape. When the
hissing sound has stopped, press
down on the cap while turning
counterclockwise and remove it.
Hard water or salt water is harmful
to the engine parts. You may use
distilled water, if you can't get soft
water.
1. Place the machine on a level
place, and hold it in an upright po-
sition.
2. Remove:
• Radiator cap
3. Check:
• Coolant level "a"
Coolant level low→Add coolant.
1. Radiator
CHANGING THE COOLANT
Do not remove the radiator cap
when the engine is hot.
Take care so that coolant does not
splash on painted surfaces. If it
splashes, wash it away with water.
1. Place a container under the en-
gine.
2. Remove:
• Coolant drain bolt "1"
3. Remove:
• Radiator cap
Drain the coolant completely.
4. Clean:
• Cooling system
Thoroughly flush the cooling sys-
tem with clean tap water.
5. Install:
• Copper washer
• Coolant drain bolt
6. Fill:
• Radiator
•Engine
To specified level.
• Do not mix more than one type of
ethylene glycol antifreeze con-
taining corrosion inhibitors for
aluminum engine.
• Do not use water containing im-
purities or oil.
Handling notes of coolant:
The coolant is harmful so it should be
handled with special care.
• When coolant splashes to your
eye.
Thoroughly wash your eye with
water and see your doctor.
• When coolant splashes to your
clothes.
Quickly wash it away with water
and then with soap.
• When coolant is swallowed.
Quickly make him vomit and take
him to a doctor.
7. Install:
• Radiator cap
Start the engine and warm it up
for a several minutes.
8. Check:
• Coolant level
Coolant level low→Add coolant.
CHECKING THE RADIATOR CAP
1. Inspect:
• Seal (radiator cap) "1"
• Valve and valve seat "2"
Crack/damage→Replace.
Exist fur deposits "3" →Clean or
replace.
CHECKING THE RADIATOR CAP
OPENING PRESSURE
1. Attach:
• Radiator cap tester "1" and adapt-
er "2"
Apply water on the radiator cap seal.
Coolant drain bolt:
10 Nm (1.0 m•kg, 7.2
ft•lb)
Recommended coolant:
High quality ethylene
glycol anti-freeze con-
taining anti-corrosion
for aluminum engine
Coolant "1" and water
(soft water) "2" mixing ra-
tio:
50%/50%
Coolant capacity:
0.9 L (0.79 Imp qt, 0.95
US qt)
Radiator cap tester:
YU-24460-01/90890-
01325
Radiator cap tester
adapter:
YU-33984/90890-01352

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)

3-8
ENGINE
LUBRICATING THE THROTTLE
1. Remove:
• Cap cover "1"
• Throttle cable cap "2"
2. Apply:
• Lithium soap base grease
On the throttle cable end "a", tube
guide cable winding portion "b"
and roller sliding surface "c".
3. Install:
• Throttle cable cap
• Cap cover
CLEANING THE AIR FILTER
ELEMENT
Proper air filter maintenance is the
biggest key to preventing premature
engine wear and damage.
Never run the engine without the
air filter element in place; this
would allow dirt and dust to enter
the engine and cause rapid wear
and possible engine damage.
1. Remove:
• Seat
• Fitting bolt "1"
• Washer "2"
• Air filter element "3"
• Air filter guide "4"2. Clean:
• Air filter element
Clean them with solvent.
After cleaning, remove the remaining
solvent by squeezing the element.
• Do not twist the element when
squeezing the element.
• Leaving too much of solvent in
the element may result in poor
starting.
3. Inspect:
• Air filter element
Damage→Replace.
4. Apply:
• Foam-air-filter oil or equivalent oil
to the element
Squeeze out the excess oil. Element
should be wet but not dripping.
5. Install:
• Air filter guide "1"
Align the projection "a" on filter guide
with the hole "b" in air filter element.
6. Apply:
• Lithium soap base grease
On the matching surface "a" on air
filter element.7. Install:
• Air filter element "1"
• Washer
• Fitting bolt
Align the projection "a" on filter guide
with the hole "b" in air filter case.
CHECKING THE TRANSMISSION
OIL LEVEL
1. Start the engine, warm it up for
several minutes and wait for five
minutes.
2. Place the machine on a level
place and hold it up on upright po-
sition by placing the suitable
stand under the engine.
3. Check:
• Transmission oil level
Transmission oil level checking
steps:
a. Remove the oil check bolt "1".
b. Inspect the oil level.
Be sure the machine is positioned
straight up when inspecting the oil
level.
Never attempt to remove the oil
check bolt just after high speed
operation. The heated oil could
spout out, causing danger. Wait
until the oil cools down.
Oil flows out→Oil level is correct.
Oil does not flow out→Oil level is
low. Add transmission oil until oil
flows out. Throttle cable cap:
1 Nm (0.1 m•kg, 0.7
ft•lb)
Fitting bolt:
2 Nm (0.2 m•kg, 1.4
ft•lb)
Recommended brand:
YAMALUBE
Recommended engine
oil type
SAE10W-40
Recommended engine
oil grade
API service SG type or
higher
JASO standard MA