steering YAMAHA YZ125LC 2010 Owners Manual

CONTENTS
CHAPTER 1
GENERAL INFOR-
MATION
LOCATION OF IMPORTANT
LABELS............................ 1-1
DESCRIPTION ................. 1-5
CONSUMER
INFORMATION................. 1-6
INCLUDED PARTS .......... 1-6
IMPORTANT
INFORMATION................. 1-6
CHECKING OF
CONNECTION .................. 1-7
SPECIAL TOOLS ............. 1-8
CONTROL
FUNCTIONS ................... 1-11
STARTING AND
BREAK-IN ...................... 1-12
TORQUE-CHECK
POINTS........................... 1-13
CLEANING AND
STORAGE ...................... 1-14
CHAPTER 2
SPECIFICATIONS
GENERAL
SPECIFICATIONS ............ 2-1
MAINTENANCE
SPECIFICATIONS ............ 2-2
TIGHTENING TORQUES . 2-7
CABLE ROUTING
DIAGRAM ....................... 2-12
CHAPTER 3
REGULAR INSPEC-
TION AND AD-
JUSTMENTS
MAINTENANCE
INTERVALS ...................... 3-1
PRE-OPERATION
INSPECTION AND
MAINTENANCE................ 3-5
ENGINE ............................ 3-6
CHASSIS .......................... 3-9
ELECTRICAL ................. 3-19
CHAPTER 4
ENGINE
SEAT, FUEL TANK AND
SIDE COVERS.................. 4-1
EXHAUST PIPE AND
SILENCER ........................ 4-3
RADIATOR ....................... 4-5
CARBURETOR AND
REED VALVE ................... 4-7
CYLINDER HEAD, CYLIN-
DER AND PISTON ......... 4-12
CLUTCH ......................... 4-19
KICK SHAFT AND
SHIFT SHAFT ................. 4-23
YPVS GOVERNOR......... 4-28
WATER PUMP................ 4-30
CDI MAGNETO............... 4-33
ENGINE REMOVAL ....... 4-35
CRANKCASE AND
CRANKSHAFT ............... 4-39
TRANSMISSION, SHIFT
CAM AND SHIFT
FORK .............................. 4-44
CHAPTER 5
CHASSIS
FRONT WHEEL AND
REAR WHEEL ..................5-1
FRONT BRAKE AND
REAR BRAKE ..................5-6
FRONT FORK .................5-16
HANDLEBAR..................5-24
STEERING ......................5-29
SWINGARM ....................5-33
REAR SHOCK
ABSORBER ....................5-38
CHAPTER 6
ELECTRICAL
ELECTRICAL
COMPONENTS AND
WIRING DIAGRAM ...........6-2
IGNITION SYSTEM...........6-3
CHAPTER 7
TUNING
ENGINE.............................7-1
CHASSIS ..........................7-6

1-6
CONSUMER INFORMATION
CONSUMER INFORMATION
There are two significant reasons for
knowing the serial number of your
machine:
1. When ordering parts, you can
give the number to your Yamaha
dealer for positive identification of
the model you own.
2. If your machine is stolen, the au-
thorities will need the number to
search for and identify your ma-
chine.
VEHICLE IDENTIFICATION
NUMBER
The vehicle identification number "1"
is stamped on the right of the steering
head pipe.
ENGINE SERIAL NUMBER
The engine serial number "1" is
stamped into the elevated part of the
right-side of the engine.
MODEL LABEL
The model label "1" is affixed to the
frame under the rider's seat. This in-
formation will be needed to order
spare parts.INCLUDED PARTS
DETACHABLE SIDESTAND
This sidestand "1" is used to support
only the machine when standing or
transporting it.
• Never apply additional force to
the sidestand.
• Remove this sidestand before
starting out.
VALVE JOINT
This valve joint "1" prevents fuel from
flowing out and is installed to the fuel
tank breather hose.
In this installation, make sure the
arrow faces the fuel tank and also
downward.
COLLAR (tool for YPVS)
This collar "1" is used to remove and
install the push rod of the engine.
NIPPLE WRENCH
This nipple wrench "1" is used to
tighten the spoke.
IMPORTANT INFORMATION
PREPARATION FOR REMOVAL
AND DISASSEMBLY
1. Remove all dirt, mud, dust, and
foreign material before removal
and disassembly.
• When washing the machine with
high pressured water, cover the
parts follows.
Silencer exhaust port
Side cover air intake port
Crankcase cover hole at the bot-
tom
Water pump housing hole at the
bottom
End of each hose
2. Use proper tools and cleaning
equipment. Refer to "SPECIAL
TOOLS" section.
3. When disassembling the ma-
chine, keep mated parts together.
They include gears, cylinders,
pistons, and other mated parts
that have been "mated" through
normal wear. Mated parts must
be reused as an assembly or re-
placed.

1-9
SPECIAL TOOLS
Fuel level gauge "1"
YM-1312-A, 90890-01312
Fuel level gauge adaptor "2"
YM-01470, 90890-01470This gauge is used to measure the
fuel level in the float chamber.
Radiator cap tester
YU-24460-01, 90890-01325
Radiator cap tester adapter
YU-33984, 90890-01352These tools are used for checking
the cooling system.
Flywheel puller
YU-33270-B, 90890-01362 These tool is used to split the crank-
case.
Steering nut wrench
YU-33975, 90890-01403 This tool is used when tighten the
steering ring nut to specification.
Cap bolt wrench
YM-01500, 90890-01500This tool is used to loosen or tighten
the base valve.
Cap bolt ring wrench
YM-01501, 90890-01501This tool is used to loosen or tighten
the damper assembly. Tool name/Part number How to use Illustration

1-13
TORQUE-CHECK POINTS
TORQUE-CHECK POINTS
Concerning the tightening torque, refer to "TIGHTENING TORQUES" section in the CHAPTER 2.
Frame construction Frame to rear frame
Combined seat and fuel tank Fuel tank to frame
Exhaust system Silencer to rear frame
Engine mounting Frame to engine
Engine bracket to engine
Engine bracket to frame
Steering Steering stem to handlebar Steering stem to frame
Steering stem to upper bracket
Upper bracket to handlebar
Suspension Front Steering stem to front fork Front fork to upper bracket
Front fork to lower bracket
Rear For link type Assembly of links
Link to frame
Link to rear shock absorber
Link to swingarm
Installation of rear shock absorber Rear shock absorber to frame
Installation of swingarm Tightening of pivot shaft
Wheel Installation of wheel Front Tightening of wheel axle
Tightening of axle holder
Rear Tightening of wheel axle
Wheel to rear wheel sprocket
Brake Front Brake caliper to front fork
Brake disc to wheel
Tightening of union bolt
Brake master cylinder to handlebar
Tightening of bleed screw
Tightening of brake hose holder
Rear Brake pedal to frame
Brake disc to wheel
Tightening of union bolt
Brake master cylinder to frame
Tightening of bleed screw
Tightening of brake hose holder
Fuel system Fuel tank to fuel cock

2-5
MAINTENANCE SPECIFICATIONS
CHASSISCooling:
Radiator core size:
Width 107.8 mm (4.24 in) ----
Height (left) 240 mm (9.45 in) ----
Height (right) 220 mm (8.66 in) ----
Thickness 32 mm (1.26 in) ----
Radiator cap opening pressure 95–125 kPa (0.95–1.25 kg/cm
2, 13.5–17.8 psi) ----
Radiator capacity (total) 0.56 L (0.49 Imp qt, 0.59 US qt) ----
Water pump:
Type Single-suction centrifugal pump ----
Item Standard Limit
Steering system:
Steering bearing typeTaper roller bearing ----
Front suspension: USA, CDN, ZA, AUS,
NZEUROPE
Front fork travel 300 mm (11.8 in)←----
Fork spring free length 454 mm (17.9 in)←449 mm (17.7
in)
Spring rate, STD K=4.1 N/mm (0.418 kg/
mm, 23.4 lb/in)←----
Optional spring Yes←----
Oil capacity 524 cm
3 (18.4 Imp oz,
17.7 US oz)526 cm3 (18.5 Imp oz,
17.8 US oz)----
Oil grade Suspension oil "S1"←----
Inner tube outer diameter 48 mm (1.89 in)←----
Front fork top end 5 mm (0.2 in)←----
Rear suspension: USA, CDN, ZA, AUS,
NZEUROPE
Shock absorber travel 131.5 mm (5.18 in)←----
Spring free length Approx.265 mm (10.43
in)←----
Fitting length*----
I.D. mark (Red/1) 258 mm (10.16 in) 252 mm (9.92 in) ----
I.D. mark (Red/2) 264 mm (10.39 in) 258 mm (10.16 in) ----
I.D. mark (Red/3) 255.5 mm (10.06 in) 249.5 mm (9.82 in) ----
Preload length
<Min.–Max> 1.5–18 mm (0.06–0.71
in)←----
Spring rate, STD K=46.0 N/mm (4.70 kg/
mm, 263.2 lb/in)←----
Optional spring Yes←----
Enclosed gas pressure 1,000 kPa (10 kg/cm
2,
142 psi)←----
* Spring specification varies according to the differ-
ence in the production lot.Item Standard Limit

2-8
TIGHTENING TORQUES
CHASSIS
△- marked portion shall be checked for torque tightening after break-in or before each race.
Carburetor joint M6 × 1.0 4 10 1.0 7.2
Carburetor joint clamp M4 × 0.7 1 2 0.2 1.4
Air filter joint clamp M4 × 0.7 1 2 0.2 1.4
△Air filter case M6 × 1.0 4 8 0.8 5.8
Air filter guide clamp M5 × 0.8 1 4 0.4 2.9
Reed valve M3 × 0.5 6 1 0.1 0.7
Throttle cable adjust bolt and locknut M8 × 1.25 1 7 0.7 5.1
Throttle cable M6 × 0.75 1 4 0.4 2.9
Crankcase M6 × 1.0 12 14 1.4 10
Right crankcase cover M6 × 1.0 8 10 1.0 7.2
Left crankcase cover M6 × 1.0 4 5 0.5 3.6
Drive chain sprocket cover M6 × 1.0 2 5 0.5 3.6
Bearing plate cover M6 × 1.0 4 10 1.0 7.2
Holder M6 × 1.0 1 10 1.0 7.2
Oil check bolt M6 × 1.0 1 10 1.0 7.2
Oil drain bolt M10 × 1.25 1 20 2.0 14
Kickstarter crank M6 × 1.0 1 10 1.0 7.2
Clutch cover M6 × 1.0 6 10 1.0 7.2
Primary drive gear M8 × 1.25 1 48 4.8 35
Clutch boss M16 × 1.0 1 80 8.0 58
Clutch spring M6 × 1.0 5 10 1.0 7.2
Clutch cable adjust bolt and locknut M6 × 0.75 1 4 0.4 2.9
Drive sprocket M18 × 1.0 1 75 7.5 54
Shift pedal M6 × 1.0 1 12 1.2 8.7
Bearing plate cover (shift cam) M6 × 1.0 2 10 1.0 7.2
Shift guide M6 × 1.0 2 10 1.0 7.2
Stopper lever M6 × 1.0 1 10 1.0 7.2
Segment M8 × 1.25 1 30 3.0 22
△Exhaust pipe M6 × 1.0 2 12 1.2 8.7
△Exhaust pipe stay (front) M6 × 1.0 1 12 1.2 8.7
△Exhaust pipe stay (rear) M6 × 1.0 1 12 1.2 8.7
Silencer:
△Silencer and frame M6 × 1.0 2 12 1.2 8.7
Fiber (For USA and CDN) M6 × 1.0 2 10 1.0 7.2
Fiber (Except for USA and CDN) M6 × 1.0 4 10 1.0 7.2Part to be tightened Thread size Q'tyTightening torque
Nm m•kg ft•lb
Part to be tightened Thread size Q'tyTightening torque
Nm m•kg ft•lb
△Upper bracket and outer tube M8 × 1.25 4 21 2.1 15
△Lower bracket and outer tube M8 × 1.25 4 21 2.1 15
△Upper bracket and steering stem M24 × 1.0 1 145 14.5 105
△Handlebar upper holder M8 × 1.25 4 28 2.8 20

2-9
TIGHTENING TORQUES
△Handlebar lower holder M12 × 1.25 2 40 4.0 29
△Steering ring nut M28 × 1.0 1 Refer to TIP.
Front fork and damper assembly M51 × 1.5 2 30 3.0 22
Front fork and adjuster M22 × 1.25 2 55 5.5 40
Damper assembly and base valve M42 × 1.5 2 29 2.9 21
Adjuster and damper assembly M12 × 1.25 2 29 2.9 21
Bleed screw (front fork) and base valve M5 × 0.8 2 1 0.1 0.7
△Front fork and front fork protector M6 × 1.0 6 5 0.5 3.6
△Cable guide (front brake hose) and lower bracket M6 × 1.0 1 4 0.4 2.9
△Front fork protector and brake hose holder M6 × 1.0 2 8 0.8 5.8
Throttle cable cap M4 × 0.7 2 1 0.1 0.7
△Front brake master cylinder and bracket M6 × 1.0 2 9 0.9 6.5
Brake lever mounting bolt M6 × 1.0 1 6 0.6 4.3
Brake lever mounting nut M6 × 1.0 1 6 0.6 4.3
Brake lever position locknut M6 × 1.0 1 5 0.5 3.6
Clutch lever mounting nut M6 × 1.0 1 4 0.4 2.9
Clutch lever holder M5 × 0.8 2 4 0.4 2.9
Front brake master cylinder cap M4 × 0.7 2 2 0.2 1.4
△Front brake hose union bolt (brake master cylinder) M10 × 1.25 1 30 3.0 22
△Front brake hose union bolt (caliper) M10 × 1.25 1 30 3.0 22
△Front brake caliper and front fork M8 × 1.25 2 28 2.8 20
Grip cap upper and lower M6 × 1.0 2 4 0.4 2.9
Brake caliper (front and rear) and pad pin plug M10 × 1.0 2 3 0.3 2.2
△Brake caliper (front and rear) and pad pin M10 × 1.0 2 18 1.8 13
△Brake caliper (front and rear) and bleed screw M8 × 1.25 2 6 0.6 4.3
△Front wheel axle and axle nut M16 × 1.5 1 105 10.5 75
△Front wheel axle holder M8 × 1.25 4 21 2.1 15
△Front brake disc and wheel hub M6 × 1.0 6 12 1.2 8.7
△Rear brake disc and wheel hub M6 × 1.0 6 14 1.4 10
Footrest bracket and frame M10 × 1.25 4 55 5.5 40
△Brake pedal mounting M8 × 1.25 1 26 2.6 19
△Rear brake master cylinder and frame M6 × 1.0 2 10 1.0 7.2
Rear brake master cylinder cap M4 × 0.7 2 2 0.2 1.4
△Rear brake hose union bolt (caliper) M10 × 1.25 1 30 3.0 22
△Rear brake hose union bolt (master cylinder) M10 × 1.25 1 30 3.0 22
△Rear wheel axle and axle nut M20 × 1.5 1 125 12.5 90
△Nipple (spoke) — 72 3 0.3 2.2
△Driven sprocket and wheel hub M8 × 1.25 6 42 4.2 30
△Disc cover and rear brake caliper M6 × 1.0 2 10 1.0 7.2
△Protector and rear brake caliper M6 × 1.0 2 7 0.7 5.1
Drive chain puller adjust bolt and locknut M8 × 1.25 2 19 1.9 13
Engine :
△Engine and frame (front) M10 × 1.25 1 64 6.4 46
△Engine and frame (lower) M10 × 1.25 1 64 6.4 46Part to be tightened Thread size Q'tyTightening torque
Nm m•kg ft•lb

2-10
TIGHTENING TORQUES
1. First, tighten the steering ring nut approximately 38 Nm (3.8 m•kg, 27 ft•lb) by using the steering nut wrench, then loosen
the steering ring nut one turn.
2. Retighten the steering ring nut 7 Nm (0.7 m•kg, 5.1 ft•lb).
ELECTRICAL △Engine bracket and frame M8 × 1.25 2 34 3.4 24
△Engine bracket and engine M8 × 1.25 1 34 3.4 24
△Pivot shaft and nut M16 × 1.5 1 85 8.5 61
△Relay arm and swingarm M14 × 1.5 1 70 7.0 50
△Relay arm and connecting rod M14 × 1.5 1 80 8.0 58
△Connecting rod and frame M14 × 1.5 1 80 8.0 58
△Rear shock absorber and frame M10 × 1.25 1 56 5.6 40
△Rear shock absorber and relay arm M10 × 1.25 1 53 5.3 38
△Rear frame and frame (upper) M8 × 1.25 1 32 3.2 23
△Rear frame and frame (lower) M8 × 1.25 2 29 2.9 21
△Swingarm and brake hose holder M5 × 0.8 4 3 0.3 2.2
Swingarm and patch M4 × 0.7 4 2 0.2 1.4
Drive chain tensioner M8 × 1.25 2 16 1.6 11
Drive chain support and swingarm M6 × 1.0 3 7 0.7 5.1
Seal guard and swingarm M5 × 0.8 4 6 0.6 4.3
Cable guide and frame M5 × 0.8 2 4 0.4 2.9
△Fuel tank boss and frame M10 × 1.25 2 20 2.0 14
△Fuel tank M6 × 1.0 2 10 1.0 7.2
△Fuel tank and fuel cock M6 × 1.0 2 4 0.4 2.9
Fuel tank and seat set bracket M6 × 1.0 1 7 0.7 5.1
Fuel tank and hooking screw (fitting band) M6 × 1.0 1 7 0.7 5.1
Fuel tank and fuel tank bracket M6 × 1.0 4 7 0.7 5.1
△Air scoop and fuel tank M6 × 1.0 4 7 0.7 5.1
△Air scoop and radiator guard (lower) M6 × 1.0 2 6 0.6 4.3
△Front fender M6 × 1.0 4 7 0.7 5.1
△Rear fender (front) M6 × 1.0 2 7 0.7 5.1
△Rear fender (rear) M6 × 1.0 2 12 1.2 8.7
△Side cover M6 × 1.0 2 7 0.7 5.1
Seat M8 × 1.25 2 19 1.9 13
△Number plate M6 × 1.0 1 7 0.7 5.1Part to be tightened Thread size Q'tyTightening torque
Nm m•kg ft•lb
Part to be tightened Thread size Q'tyTightening torque
Nm m•kg ft•lb
Stator M6 × 1.0 3 7 0.7 5.1
Rotor M12 × 1.25 1 56 5.6 40
Ignition coil M6 × 1.0 2 7 0.7 5.1

3-3
MAINTENANCE INTERVALS
BRAKES
Adjust lever position and
pedal height●●
Lubricate pivot point●●
Check brake disc surface●●
Check fluid level and leak-
age●●
Retighten brake disc bolts,
caliper bolts, master cylin-
der bolts and union bolts●●
Replace pads●
Replace brake fluid●Every one year
FRONT FORKS
Inspect and adjust●●
Replace oil●●Suspension oil "S1"
Replace oil seal●
FRONT FORK OIL SEAL
AND DUST SEAL
Clean and lube●●Lithium base grease
PROTECTOR GUIDE
Replace●
REAR SHOCK ABSORBER
Inspect and adjust●●
Lube●(After rain
ride)●Molybdenum disulfide grease
Replace spring seat●Every one year
Retighten●●
DRIVE CHAIN GUIDE AND
ROLLERS
Inspect●●
SWINGARM
Inspect, lube and retighten●●Molybdenum disulfide grease
RELAY ARM, CONNECT-
ING ROD
Inspect, lube and retighten●●Molybdenum disulfide grease
STEERING HEAD
Inspect free play and re-
tighten●●
Clean and lube●Lithium base grease
Replace bearing● ItemAfter
break-in
Every
race
(about
2.5
hours)Every
third
(about
7.5
hours)Every
fifth
(about
12.5
hours)
As re-
quiredRemarks

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