2012 YAMAHA YZ125LC Owners Manual

2-1
GENERAL SPECIFICATIONS
SPECIFICATIONS
GENERAL SPECIFICATIONS
Model name: YZ125B (USA, CDN, AUS, NZ)
YZ125 (EUROPE, ZA)
Model code number: 1SR1 (USA, CDN)
1SR2 (EUROPE)
1SR4 (AUS, NZ, ZA)
Dimensions: USA, AUS, NZ, ZA EUROPE, CDN
Overall length 2,135 mm (84.1 in) 2,139 mm (84.2 in)
Overall width 827 mm (32.6 in)←
Overall height 1,315 mm (51.8 in) 1,318 mm (51.9 in)
Seat height 997 mm (39.3in) 998 mm (39.3 in)
Wheelbase 1,443 mm (56.8 in)←
Minimum ground clearance 386 mm (15.2 in) 388 mm (15.3 in)
Weight:
Curb weight 94 kg (207 lb)
Engine:
Engine type Liquid cooled 2-stroke, gasoline
Cylinder arrangement Single cylinder
Displacement 124 cm
3 (4.36 Imp oz, 4.19 US oz)
Bore × stroke 54 × 54.5 mm (2.126 × 2.146 in)
Compression ratio 8.6–10.7 : 1
Starting system Kick starter
Lubrication system: Premix (30 : 1)(Yamalube 2-R)
Oil type or grade (2-stroke):
Transmission oil Recommended brand: YAMALUBE
SAE10W-40
API service SG type or higher
JASO standard MA
Periodic oil change 0.66 L (0.58 Imp qt, 0.69 US qt)
Total amount 0.70 L (0.62 Imp qt, 0.74 US qt)
Coolant capacity (including all routes): 0.9 L (0.79 Imp qt, 0.95 US qt)
Air filter: Wet type element
Fuel:
Type Premium unleaded gasoline only with a research octane
number of 95 or higher.
Tank capacity 8.0 L (1.76 Imp gal, 2.11 US gal)
Carburetor:
Type/Manufacturer TMXχ38SS/MIKUNI
Spark plug:
Type/Manufacturer BR9EVX/NGK (resistance type)
Gap 0.6–0.7 mm (0.024–0.028 in)
Clutch type: Wet, multiple-disc
2

2-2
MAINTENANCE SPECIFICATIONS
MAINTENANCE SPECIFICATIONS
ENGINETransmission:
Primary reduction system Gear
Primary reduction ratio 3.368 (64/19)
Final drive Chain
Secondary reduction ratio 3.692 (48/13)
Transmission type Constant mesh, 6-speed
Operation Left foot operation
Gear ratio:
1st 2.385 (31/13)
2nd 1.933 (29/15)
3rd 1.588 (27/17)
4th 1.353 (23/17)
5th 1.200 (24/20)
6th 1.095 (23/21)
Chassis: USA, ZA, AUS, NZ EUROPE, CDN
Frame type Semi double cradle←
Caster angle 25.50 ° 25.60 °
Trail 105 mm (4.13 in) 107 mm (4.21 in)
Tire:
Type With tube
Size (front) 80/100-21 51M
Size (rear) 100/90-19 57M
Tire pressure (front and rear) 100 kPa (1.0 kgf/cm
2, 15 psi)
Brake:
Front brake type Single disc brake
Operation Right hand operation
Rear brake type Single disc brake
Operation Right foot operation
Suspension:
Front suspension Telescopic fork
Rear suspension Swingarm (link type monocross suspension)
Shock absorber:
Front shock absorber Coil spring/oil damper
Rear shock absorber Coil spring/gas, oil damper
Wheel travel:
Front wheel travel 300 mm (11.8 in)
Rear wheel travel 315 mm (12.4 in)
Electrical:
Ignition system CDI magneto
Item Standard Limit
Cylinder head:
Combustion chamber volume 8.4 cm
3 (0.296 Imp oz, 0.284 US oz) ----
Warp limit ---- 0.03 mm
(0.0012 in)

2-3
MAINTENANCE SPECIFICATIONS
Cylinder:
Bore size 54.000–54.014 mm (2.1260–2.1265 in) 54.1 mm
(2.130 in)
Taper limit ---- 0.05 mm
(0.0020 in)
Out of round limit ---- 0.01 mm
(0.0004 in)
Piston:
Piston size/ 53.957–53.972 mm (2.1243–2.1249 in) ----
Measuring point "H" 17.5 mm (0.69 in) ----
Piston clearance 0.040–0.045 mmm (0.0016–0.0018 in) 0.1 mm (0.004
in)
Piston offset 0.5 mm (0.019 in)/EX-side ----
Piston pin:
Piston pin outside diameter 14.995–15.000 mm (0.5904–0.5906 in) 14.975 mm
(0.5896 in)
Piston ring:
Sectional sketch Plain ----
B=1.0 mm (0.039 in) ----
T=2.35 mm (0.093 in) ----
End gap (installed) 0.5–0.7 mm (0.020–0.028 in) 1.2 mm (0.047
in)
Side clearance (installed) 0.035–0.070 mm (0.0014~0.0028 in) 0.1 mm (0.004
in)
Crankshaft:
Crank width "A" 55.90–55.95 mm (2.201–2.203 in) ----
Runout limit "C" 0.03 mm (0.0012 in) 0.05 mm
(0.0020 in)
Connecting rod big end side clearance "D" 0.06–0.64 mm (0.002–0.025 in) ----
Small end free play "F" 0.8–1.0 mm (0.031–0.039 in) 2.0 mm (0.08
in) Item Standard Limit

2-4
MAINTENANCE SPECIFICATIONS
Clutch:
Friction plate thickness 2.9–3.1 mm (0.114–0.122 in) 2.8 mm (0.110
in)
Quantity 8 ----
Clutch plate thickness 1.5–1.7 mm (0.059–0.067 in) ----
Quantity 7 ----
Warp limit ---- 0.2 mm (0.008
in)
Clutch spring free length 40.1 mm (1.579 in) 38.1 mm
(1.500 in)
Quantity 5 ----
Clutch housing thrust clearance 0.15–0.26 mm (0.006–0.010 in) ----
Clutch housing radial clearance 0.014–0.046 mm (0.0006–0.0018 in) ----
Clutch release methodInner push, cam push ----
Transmission:
Main axle deflection limit ---- 0.01 mm
(0.0004 in)
Drive axle deflection limit ---- 0.01 mm
(0.0004 in)
Shifter:
Shifting type Cam drum and guide bar ----
Guide bar bending limit ---- 0.05 mm
(0.0020 in)
Kick starter type: Kick and mesh type ----
Kick clip friction force P=0.8–1.2 kg (1.8–2.6 lb) ----
Air filter oil grade (oiled filter): Foam-air-filter oil or equivalent oil ----
Carburetor: USA, CDN EUROPE AUS, NZ, ZA
Type/Manufacturer TMXχ38SS/
MIKUNI←←
I.D. mark 1C37 51 1C36 41←----
Main jet (M.J.) #430←←----
Jet needle-clip position (J.N.) 6BFY43-74-3←←----
Cutaway (C.A.) 4.0←←----
Pilot jet (P.J.) #40 #45←----
Pilot air screw (P.A.S.) 2-1/4←←----
Valve seat size (V.S.) ø3.8 mm (0.15
in)←←----
Starter jet (G.S.) #80←←----
Fuel level (F.L.) 9.5–10.5 mm
(0.37–0.41 in)←←----
Reed valve:
Thickness 0.47 mm (0.019 in) ----
Valve stopper height 8.2–8.6 mm (0.323–0.339 in) ----
Valve bending limit ---- 0.2 mm (0.008
in) Item Standard Limit

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
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

2-6
MAINTENANCE SPECIFICATIONS
Swingarm:
Swingarm free play limit
End ---- 1.0 mm (0.04
in)
Side clearance ---- 0.2–0.9 mm
(0.008–0.035
in)
Wheel:
Front wheel type Spoke wheel ----
Rear wheel typeSpoke wheel ----
Front rim size/material 21 × 1.60/Aluminum ----
Rear rim size/material 19 × 1.85/Aluminum ----
Rim runout limit:
Radial ---- 2.0 mm (0.08
in)
Lateral ---- 2.0 mm (0.08
in)
Drive chain:
Type/manufacturer DID520DMA2 SDH G&B/DAIDO ----
Number of links 111 links + joint ----
Chain slack 48–58 mm (1.9–2.3 in) ----
Chain length (15 links) ---- 242.9 mm
(9.563 in)
Front disc brake:
Disc outside dia.×Thickness 250 × 3.0 mm (9.84 × 0.12 in) 250 × 2.5 mm
(9.84 × 0.10 in)
Pad thickness 4.4 mm (0.17 in) 1.0 mm (0.04
in)
Master cylinder inside dia. 9.52 mm (0.375 in) ----
Caliper cylinder inside dia. 22.65 mm (0.892 in) × 2 ----
Brake fluid type DOT #4 ----
Rear disc brake:
Disc outside dia.×Thickness 245 × 4.0 mm (9.65 × 0.16 in) 245 × 3.5 mm
(9.65 × 0.14 in)
Deflection limit ---- 0.15 mm
(0.006 in)
Pad thickness 6.4 mm (0.25 in) 1.0 mm (0.04
in)
Master cylinder inside dia. 11.0 mm (0.433 in) ----
Caliper cylinder inside dia. 25.4 mm (1.000 in) × 1 ----
Brake fluid type DOT #4 ----
Brake lever and brake pedal:
Brake lever position 95 mm (3.74 in) ----
Brake pedal height (vertical height above footrest
top)Zero mm (Zero in) ----
Clutch lever free play (lever end) 8–13 mm (0.31–0.51 in) ----
Throttle grip free play3–5 mm (0.12–0.20 in) ---- Item Standard Limit

2-7
TIGHTENING TORQUES
ELECTRICAL
TIGHTENING TORQUES
ENGINE
△- marked portion shall be checked for torque tightening after break-in or before each race.
Item Standard Limit
Ignition system:
Ignition timing (B.T.D.C.) 0.48 mm (0.019 in) ----
Advancer type Electrical ----
CDI:
Magneto-model (stator)/Manufacturer 1C3-10/YAMAHA ----
Charging coil 1 resistance (color) 720–1,080 Ωat 20 °C (68 °F) (Green/
White-Black/Red)----
Charging coil 2 resistance (color) 44–66 Ωat 20 °C (68 °F) (Black-Green/
Blue)----
Pickup coil resistance (color) 248–372 Ωat 20 °C (68 °F) (White/Blue-
White/Red)----
CDI unit-model/manufacturer 1C3-10/YAMAHA ----
Ignition coil:
Model/manufacturer 1C3-00/YAMAHA ----
Minimum spark gap 6 mm (0.24 in) ----
Primary winding resistance 0.24–0.36 Ωat 20 °C (68 °F) ----
Secondary winding resistance 5.7–8.5 kΩat 20 °C (68 °F) ----
Spark plug cap:
Resistance 4–6 kΩat 20 °C (68 °F) ----
ItemThread
sizeQ'ty Tightening torque Remarks
Spark plug M14S 1 20 Nm (2.0 m•kg, 14 ft•lb)
Cylinder head (nut) M8 5 28 Nm (2.8 m•kg, 20 ft•lb)Copper
washer
Cylinder head (stud) M8 5 13 Nm (1.3 m•kg, 9.4 ft•lb)
Cylinder (nut) M8 4 30 Nm (3.0 m•kg, 22 ft•lb)
Cylinder (stud) M10 4 13 Nm (1.3 m•kg, 9.4 ft•lb)
Power valve:
Cover M5 4 5 Nm (0.5 m•kg, 3.6 ft•lb) YPVS
Link lever M4 1 4 Nm (0.4 m•kg, 2.9 ft•lb) YPVS
Holder (power valve) M5 4 8 Nm (0.8 m•kg, 5.8 ft•lb) YPVS
Push rod M5 1 5 Nm (0.5 m•kg, 3.6 ft•lb) YPVS
Thrust plate M5 1 4 Nm (0.4 m•kg, 2.9 ft•lb) YPVS
Governor fork M4 2 5 Nm (0.5 m•kg, 3.6 ft•lb) YPVS
Housing M5 3 4 Nm (0.4 m•kg, 2.9 ft•lb) YPVS
Water pump housing cover M6 4 10 Nm (1.0 m•kg, 7.2 ft•lb)
Coolant drain bolt M6 1 10 Nm (1.0 m•kg, 7.2 ft•lb)Copper
washer
Radiator M6 6 10 Nm (1.0 m•kg, 7.2 ft•lb)
Radiator panel M6 2 10 Nm (1.0 m•kg, 7.2 ft•lb)
Radiator hose clamp M6 8 2 Nm (0.2 m•kg, 1.4 ft•lb)

2-8
TIGHTENING TORQUES
Air filter element M6 1 2 Nm (0.2 m•kg, 1.4 ft•lb)
Carburetor joint M6 4 10 Nm (1.0 m•kg, 7.2 ft•lb)
Carburetor joint clamp M4 1 2 Nm (0.2 m•kg, 1.4 ft•lb)
Air filter joint clamp M4 1 2 Nm (0.2 m•kg, 1.4 ft•lb)
△Air filter case M6 4 8 Nm (0.8 m•kg, 5.8 ft•lb)
Air filter guide clamp M5 1 4 Nm (0.4 m•kg, 2.9 ft•lb)
Reed valve M3 6 1 Nm (0.1 m•kg, 0.7 ft•lb)
Throttle cable adjust bolt and locknut M8 1 7 Nm (0.7 m•kg, 5.1 ft•lb)
Throttle cable M6 1 4 Nm (0.4 m•kg, 2.9 ft•lb)
Crankcase M6 12 14 Nm (1.4 m•kg, 10 ft•lb)
Right crankcase cover M6 8 10 Nm (1.0 m•kg, 7.2 ft•lb)
Left crankcase cover M6 4 5 Nm (0.5 m•kg, 3.6 ft•lb)
Drive chain sprocket cover M6 2 5 Nm (0.5 m•kg, 3.6 ft•lb)
Bearing plate cover M6 4 10 Nm (1.0 m•kg, 7.2 ft•lb)
Holder M6 1 10 Nm (1.0 m•kg, 7.2 ft•lb)
Oil check bolt M6 1 10 Nm (1.0 m•kg, 7.2 ft•lb)Copper
washer
Oil drain bolt M10 1 20 Nm (2.0 m•kg, 14 ft•lb)Copper
washer
Kickstarter crank M6 1 10 Nm (1.0 m•kg, 7.2 ft•lb)
Clutch cover M6 6 10 Nm (1.0 m•kg, 7.2 ft•lb)
Primary drive gear M8 1 48 Nm (4.8 m•kg, 35 ft•lb)
Clutch boss M16 1 80 Nm (8.0 m•kg, 58 ft•lb) Lock washer
Clutch spring M6 5 10 Nm (1.0 m•kg, 7.2 ft•lb)
Clutch cable adjust bolt and locknutM6 1 4 Nm (0.4 m•kg, 2.9 ft•lb)
Drive sprocket M18 1 75 Nm (7.5 m•kg, 54 ft•lb) Lock washer
Shift pedal M6 1 12 Nm (1.2 m•kg, 8.7 ft•lb)
Bearing plate cover (shift cam) M6 2 10 Nm (1.0 m•kg, 7.2 ft•lb)
Shift guide M6 2 10 Nm (1.0 m•kg, 7.2 ft•lb)
Stopper lever M6 1 10 Nm (1.0 m•kg, 7.2 ft•lb)
Segment M8 1 30 Nm (3.0 m•kg, 22 ft•lb)
△Exhaust pipe M6 2 12 Nm (1.2 m•kg, 8.7 ft•lb)
△Exhaust pipe stay (front) M6 1 12 Nm (1.2 m•kg, 8.7 ft•lb)
△Exhaust pipe stay (rear) M6 1 12 Nm (1.2 m•kg, 8.7 ft•lb)
Silencer:
△Silencer and frame M6 2 12 Nm (1.2 m•kg, 8.7 ft•lb)
Fiber M6 4 10 Nm (1.0 m•kg, 7.2 ft•lb)ItemThread
sizeQ'ty Tightening torque Remarks