2012 YAMAHA YZ125LC width

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

2-3
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

2-5
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

4-41
CRANKCASE AND CRANKSHAFT
REMOVING THE SEGMENT
1. Remove:
• Bolt (segment) "1"
• Segment "2"
Turn the segment counterclockwise
until it stops and loosen the bolt.
If the segment gets an impact, it
may be damaged. Take care not to
give an impact to the segment
when removing the bolt.
DISASSEMBLING THE
CRANKCASE
1. Remove:
• Crankcase (right) "1"
Use the flywheel puller "2".
• Make appropriate bolts "3" as
shown available by yourself and at-
tach the tool with them.
• Fully tighten the tool holding bolts,
but make sure the tool body is par-
allel with the case. If necessary,
one screw may be backed out
slightly to level tool body.
• As pressure is applied, alternately
tap on the engine mounting boss
and transmission shafts.
Use soft hammer to tap on the
case half. Tap only on reinforced
portions of case. Do not tap on
gasket mating surface. Work slow-
ly and carefully. Make sure the
case halves separate evenly. If one
end "hangs up", take pressure off
the push screw, realign, and start
over. If the cases do not separate,
check for a remaining case bolt or
fitting. Do not force.
REMOVING THE CRANKSHAFT
1. Remove:
• Crankshaft "1"
Use the crankcase separating
tool "2".
Make appropriate bolts "3" as shown
available by yourself and attach the
tool with them.
Do not use a hammer to drive out
the crankshaft.
REMOVING THE CRANKCASE
BEARING
1. Remove:
•Bearing "1"
• Remove the bearing from the
crankcase by pressing its inner race
as shown in "A".
• If the bearing is removed together
with the crankshaft, remove the
bearing using a general bearing
puller "2" as shown in "B".
• Do not use the removed bearing.
CHECKING THE CRANKCASE
1. Inspect:
• Contacting surface "a"
Scratches→Replace.
• Engine mounting boss "b", crank-
case
Cracks/damage→Replace.
2. Inspect:
• Bearing "1"
Rotate inner race with a finger.
Rough spot/seizure→Replace.
3. Inspect:
• Oil seal "1"
Damage→Replace.
CHECKING THE CRANKSHAFT
1. Measure:
• Runout limit "a"
• Small end free play limit "b"
• Connecting rod big end side
clearance "c"
• Crank width "d"
Out of specification→Replace.
Use the dial gauge and a thick-
ness gauge. Flywheel puller:
YU-1362-A/90890-
01362
Crankcase separating
tool:
YU-1135-A/90890-
01135
Dial gauge and stand:
YU-3097/90890-01252

4-42
CRANKCASE AND CRANKSHAFT
INSTALLING THE CRANKCASE
BEARING
1. Install:
• Bearing "1"
To left and right crankcase.
Install the bearing by pressing its out-
er race parallel.
INSTALLING THE OIL SEAL
1. Install:
• Oil seal (left) "1"
• Oil seal (right) "2"
• Apply the lithium soap base grease
on the oil seal lip.
• Install the oil seal with its manufac-
ture's marks or numbers facing out-
ward.
INSTALLING THE CRANKSHAFT
1. Install:
• Crankshaft "1"
Use the crankshaft installing tool
"2", "3", "4".
• Hold the connecting rod at top dead
center with one hand while turning
the nut of the installing tool with the
other. Operate the installing tool un-
til the crankshaft bottoms against
the bearing.
• Before installing the crankshaft,
clean the contacting surface of
crankcase.
• Apply molybdenum disulfide grease
to the surface "a" where the crank-
shaft and bearing come in contact.
• Apply the lithium soap base grease
on the oil seal lip.
Do not use a hammer to drive in
the crankshaft.
A. For USA and CDN
B. Except for USA and CDN2. Check:
• Shifter operation
• Transmission operation
Unsmooth operation→Repair.
3. Apply:
• Sealant
On the right crankcase "1".
Clean the contacting surface of left
and right crankcase before applying
the sealant.
4. Install:
• Dowel pin "1"
• O-ring "2"
5. Install:
• Right crankcase "1"
Use the crankshaft installing tool
"2", "3", "4". Standard
Runout
limit:0.03 mm
(0.0012 in)0.05 mm
(0.002 in)
Small
end free
play:0.8–1.0 mm
(0.031–0.03
9 in)2.0 mm
(0.08 in)
Side
clear-
ance:0.06–0.64
mm
(0.002–0.02
5 in)—
Crack
width:55.90–55.95
mm
(2.201–2.20
3 in)—
Crankshaft installing pot
"2":
YU-90050/90890-01274
Crankshaft installing bolt
"3":
YU-90050/90890-01275
Adapter "4":
YU-90063/90890-01278
YAMAHA Bond No.1215
(ThreeBond® No.1215):
90890-85505
Crankshaft installing pot
"2":
YU-90050/90890-01274
Crankshaft installing bolt
"3":
YU-90050/90890-01275
Adapter "4":
YM-01499/90890-01499