fuel YAMAHA YZ125LC 2004 User Guide

1-14
GEN
INFO
STARTING AND BREAK-IN
EC194001
BREAK-IN PROCEDURES
1. Before starting the engine, fill the fuel tank
with a break-in oil-fuel mixture as follows.
2. Perform the pre-operation checks on the
machine.
3. Start and warm up the engine. Check the
idle speed, and check the operation of the
controls and the “ENGINE STOP” button.
4. Operate the machine in the lower gears at
moderate throttle openings for five to eight
minutes. Stop and check the spark plug
condition; it will show a rich condition during
break-in.
5. Allow the engine to cool. Restart the engine
and operate the machine as in the step
above for five minutes. Then, very briefly
shift to the higher gears and check full-throt-
tle response. Stop and check the spark
plug.
6. After again allowing the engine to cool,
restart and run the machine for five more
minutes. Full throttle and the higher gears
may be used, but sustained full-throttle op-
eration should be avoided. Check the spark
plug condition.
7. Allow the engine to cool, remove the top
end, and inspect the piston and cylinder.
Remove any high spots on the piston with
#600 grit wet sandpaper. Clean all compo-
nents and carefully reassemble the top end.
8. Drain the break-in oil-fuel mixture from the
fuel tank and refill with the specified mix.
9. Restart the engine and check the operation
of the machine throughout its entire operat-
ing range. Stop and check the spark plug
condition. Restart the machine and operate
it for about 10 to 15 more minutes. The ma-
chine will now be ready to race.
Mixing oil: Mixing ratio:
Yamalube “2-R” 15:1
5XE-9-30-1B 3/24/03 11:06 PM Page 6

1-16
GEN
INFO
TORQUE-CHECK POINTS
EC1A0013
TORQUE-CHECK POINTS
Frame construction Frame to rear frame
Combined seat and tank Fuel tank to frame
Engine mounting Frame to engine
Engine bracket to engine
Engine bracket to frame
Steering Steering shaft to Steering shaft to frame
handlebar Steering shaft to handle crown
Handle crown to handlebar
Suspension Front Steering shaft to Front fork to handle crown
front fork Front fork to under bracket
Rear For link type Assembly of links
Link to frame
Link to shock absorber
Link to swingarm
Rear Installation of shock Shock absorber to frame
absorber
Rear Installation of swingarm Tightening of pivot shaft
Wheel Installation of wheel Front Tightening of front axle
Tightening of axle holder
Rear Tightening of rear axle
Wheel to sprocket
Brake Front Caliper to front fork
Brake disc to wheel
Tightening of union bolt
Master cylinder to handlebar
Tightening of air bleeder
Rear Brake pedal to frame
Brake disc to wheel
Tighening of union bolt
Master cylinder to frame
Tightening of air bleeder
Fuel system Fuel tank to fuel cock
NOTE:
Concerning the tightening torque, refer to “
MAINTENANCE SPECIFICATIONS” section in
the CHAPTER 2.
5XE-9-30-1B 3/24/03 11:06 PM Page 10

1-18
GEN
INFO
CLEANING AND STORAGE
EC1B2001
STORAGE
If your machine is to be stored for 60 days or
more, some preventive measures must be taken
to avoid deterioration. After cleaning the ma-
chine thoroughly, prepare it for storage as fol-
lows:
1. Drain the fuel tank, fuel lines, and the carbu-
retor float bowl.
2. Remove the spark plug, pour a tablespoon
of SAE 10W-30 motor oil in the spark plug
hole, and reinstall the plug. With the engine
stop switch pushed in, kick the engine over
several times to coat the cylinder walls with
oil.
3. Remove the drive chain, clean it thoroughly
with solvent, and lubricate it. Reinstall the
chain or store it in a plastic bag tied to the
frame.
4. Lubricate all control cables.
5. Block the frame up to raise the wheels off
the ground.
6. Tie a plastic bag over the exhaust pipe out-
let to prevent moisture from entering.
7. If the machine is to be stored in a humid or
salt-air environment, coat all exposed metal
surfaces with a film of light oil. Do not apply
oil to rubber parts or the seat cover.
NOTE:
Make any necessary repairs before the machine
is stored.
5XE-9-30-1B 3/24/03 11:06 PM Page 16

2-1
SPECGENERAL SPECIFICATIONS
Model name: YZ125LC (EUROPE)
YZ125S (USA)
YZ125(S) (CDN, AUS, NZ, ZA)
Model code number: 5XE1 (USA, CDN, ZA)
5XE2 (EUROPE)
5XE4 (AUS, NZ)
Dimensions:USA, ZAAUS, NZ EUROPE CDN
Overall length 2,134 mm←2,130 mm←
(84.0 in) (83.9 in)
Overall width 827 mm←←←
(32.6 in)
Overall height 1,318 mm 1,315 mm 1,311 mm 1,315 mm
(51.9 in) (51.8 in) (51.6 in) (51.8 in)
Seat height 993 mm←992 mm←
(39.1 in) (39.1 in)
Wheelbase 1,438 mm←←←
(56.6 in)
Minimum ground clearance 400 mm←398 mm←
(15.7 in) (15.7 in)
Dry weight:
Without oil and fuel 87.0 kg (191.8 lb)
Engine:
Engine type Liquid cooled 2-stroke, gasoline
Cylinder arrangement Single cylinder, forward inclined
Displacement 124 cm
3(4.36 lmp oz, 4.19 US oz)
Bore ×Stroke 54 ×54.5 mm (2.126 ×2.146 in)
Compression ratio 8.7~11.0 : 1
Starting system Kick starter
Lubrication system: Premix (30 : 1)(Yamalube 2-R)
Oil type or grade (2-Cycle):
Transmission oil Yamalube 4 (10W-30) or SAE 10W-30 type SE
motor oil
Periodic oil change 0.65 L (0.57 Imp qt, 0.69 US qt)
Total amount 0.70 L (0.62 Imp qt, 0.74 US qt)
Coolant capacity (including all routes): 0.95 L (0.84 Imp qt, 1.00 US qt)
Air filter: Wet type element
Fuel:
Type Except for ZA: Premium unleaded gasoline
only with a research octane
number of 95 or higher
For ZA: Premium gasoline
Tank capacity 8.0 L (1.76 Imp gal, 2.11 US gal)
EC200000
SPECIFICATIONSEC211000
GENERAL SPECIFICATIONS
5XE-9-30-2A 5/10/03 1:57 PM Page 2

2-4
SPECMAINTENANCE SPECIFICATIONS
Item Standard Limit
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, ZA
EUROPE
AUS, NZ
Type/Manufacturer TMXχ
38SS←
/MIKUNI
I.D. mark 5XE1 00 5XE2 10…
Main jet (M.J.) #410←…
Jet needle-clip position (J.N.) 6CHY6-81-3 6CHY6-80-3…
Cutaway (C.A.) 4.0←…
Pilot jet (P.J.) #40 #37.5…
Pilot air screw (P.A.S.) 1-3/4 2…
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)
Cooling:
Radiator core size:
Width 107.8 mm (4.24 in)…
Height (left) 240 mm (9.45 in)…
(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) 0.63 L (0.55 Imp qt, 0.67 US qt)…
Water pump:
Type Single-suction centrifugal pump…
5XE-9-30-2A 5/10/03 1:57 PM Page 5

2-10
SPECMAINTENANCE SPECIFICATIONS
Part to be tightened Thread size Q'tyT ightening torqueNm m•kg ft•lb
Rear brake master cylinder and frame M 6 ×1.0 2 10 1.0 7.2
Rear brake master cylinder cap M 4 ×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 nut M20 ×1.5 1 125 12.5 90
Nipple (spoke) – 72 3 0.3 2.2
Driven sprocket and wheel hub M 8 ×1.25 6 42 4.2 30
Disc cover and rear brake caliper M 6 ×1.0 2 7 0.7 5.1
Protector and rear brake caliper M 6 ×1.0 2 7 0.7 5.1
Chain puller adjust bolt and locknut M 8 ×1.25 2 16 1.6 11
Engine mounting:
Engine and frame (front) M10 ×1.25 1 64 6.4 46
Engine and frame (lower) M10 ×1.25 1 64 6.4 46
Engine bracket and frame M 8 ×1.25 2 34 3.4 24
Engine bracket and engine M 8 ×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 80 8.0 58
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) M 8 ×1.25 1 32 3.2 23
Rear frame and frame (lower) M 8 ×1.25 2 29 2.9 21
Swingarm and brake hose holder M 5 ×0.8 4 1 0.1 0.7
Swingarm and patch M 4 ×0.7 4 2 0.2 1.4
Chain tensioner mounting M 8 ×1.25 2 19 1.9 13
Chain support and swingarm M 6 ×1.0 3 7 0.7 5.1
Seal guard and swingarm M 5 ×0.8 4 6 0.6 4.3
Fuel tank mounting M 6 ×1.0 2 10 1.0 7.2
Fuel tank and fuel cock M 6 ×1.0 2 7 0.7 5.1
Fuel tank and seat set bracket M 6 ×1.0 1 7 0.7 5.1
Fuel tank and hooking screw (fitting band) M 6 ×1.0 1 7 0.7 5.1
Fuel tank and fuel tank bracket M 6 ×1.0 4 7 0.7 5.1
Air scoop mounting M 6 ×1.0 6 4 0.4 2.9
Front fender mounting M 6 ×1.0 4 7 0.7 5.1
Rear fender mounting (front) M 6 ×1.0 2 7 0.7 5.1
Rear fender mounting (rear) M 6 ×1.0 2 12 1.2 8.7
Side cover mounting M 6 ×1.0 2 7 0.7 5.1
Seat mounting M 8 ×1.25 2 19 1.9 13
Number plate M 6 ×1.0 1 7 0.7 5.1
NOTE:

- marked portion shall be checked for torque tightening after break-in or before each race.


 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5XE-9-30-2A 5/10/03 1:57 PM Page 11

2-13
SPECCABLE ROUTING DIAGRAM
EC240000
CABLE ROUTING DIAGRAM
1Brake hose
2Cable guide
3“ENGINE STOP” button lead
4Fuel tank breather hose
5Clamp
6Throttle cable
7Wireharness
8YPVS breather hose
9Radiator breather hose
0CDI magneto lead
q“ENGINE STOP” button lead
connector
wAir vent hose (left)
eOverflow hose
rAir vent hose (right)
tTransmission oil breather hoseAFasten the ground lead
together with the front
installation portion of the
ignition coil.
BPass the throttle cable and
“ENGINE STOP” button lead
into the cable guide. Align
with the cable guide the
front end of the tape on the
throttle cable.
CPass the fuel tank breather
hose between the handlebar
and tension bar, then insert
its end into the hole of the
number plate.
DPass the throttle cable and
“ENGINE STOP” button lead
over the radiator hose.
EClamp the throttle cable,
“ENGINE STOP” button lead
and wireharness to the main
pipe.FPass the wireharness on the
outside of the “ENGINE STOP”
button lead.
GClamp the throttle cable and
wireharness to the main pipe.
HPass the transmission oil
breather hose, air vent hoses
and overflow hose between
the frame and connecting rod.
IPass the radiator breather
hose and YPVS breather hose
outside the engine bracket
and inside the down tube. Then
pass the radiator breather
hose inside the YPVS
breather hose.
JClamp the radiator breather
hose and CDI magneto lead
on the rear of the down-tube.
5XE-9-30-2B 5/10/03 1:57 PM Page 26

3-2
MAINTENANCE INTERVALS
INSP
ADJ
Item Remarks
COOLING SYSTEM
Check coolant level and leakage
Check radiator cap operation
Replace coolantEvery two years
Inspect hoses
OUTSIDE NUTS AND BOLTS Refer to “STARTING
RetightenAND BREAK-IN” section
in the CHAPTER 1.
AIR FILTER
Clean and lubricateUse foam air-filter oil or
Replaceequivalent oil
FRAME
Clean and inspect
FUEL TANK, COCK
Clean and inspect
BRAKES
Adjust lever position and pedal height
Lubricate pivot point
Check brake disc surface
Check fluid level and leakage
Retighten brake disc bolts, caliper bolts,

master cylinder bolts and union bolts
Replace pads
Replace brake fluidEvery one year
FRONT FORKS
Inspect and adjust
Replace oilSuspension oil “01”
Replace oil seal
FRONT FORK OIL SEAL AND DUST SEAL
Clean and lubeLithium base grease
REAR SHOCK ABSORBER
(After
Inspect and adjustrain ride)
Lube Molybdenum disulfide grease
Retighten
CHAIN GUARD AND ROLLERS
Inspect
SWINGARM
Inspect, lube and retightenMolybdenum disulfide grease
RELAY ARM, CONNECTING ROD
Inspect, lube and retightenMolybdenum disulfide grease
STEERING HEAD
Inspect free play and retighten
Clean and lubeLithium base grease
Replace bearing
TIRE, WHEELS
Inspect air pressure, wheel run-out,

tire wear and spoke looseness
Retighten sprocket bolt
Inspect bearings
Replace bearings
LubricateLithium base grease
THROTTLE, CONTROL CABLE
Check routing and connectionYamaha cable lube or
LubricateSAE 10W-30 motor oil
After
break-
inEvery
raceEvery
thirdEvery
fifthAs re-
quired
3
5XE-9-30-3A 4/28/03 5:55 PM Page 3

3-4
PRE-OPERATION INSPECTION AND MAINTENANCE
INSP
ADJ
EC320000
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.
EC321000
GENERAL INSPECTION AND MAINTENANCE
Item Routine Page
Coolant Check that coolant is filled up to the radiator filler cap.
Check the cooling system for leakage.P3-5~9
Fuel Check that a fresh mixture of oil and gasoline is filled in
the fuel tank. Check the fuel line for leakage.P1-12
Transmission oil Check that the oil level is correct. Check the crankcase
for leakage.P3-12~14
Gear shifter and clutch Check that gears can be shifted correctly in order and
that the clutch operates smoothly.P3-9
Throttle grip/Housing Check that the throttle grip operation and free play
are correctly adjusted. Lubricate the throttle grip and P3-10~11
housing, if necessary.
Brakes Check the play of front brake and effect of front and
rear brake.P3-17~23
Chain Check chain slack and alignment. Check that the chain
is lubricated properly.P3-24~26
Wheels Check for excessive wear and tire pressure. Check for
loose spokes and have no excessive play.P3-34~35
Steering Check that the handlebar can be turned smoothly and
have no excessive play.P3-35~36
Front forks and Check that they operate smoothly and there is no oil
rear shock absorber leakage.P3-26~33
Cables (wires) Check that the clutch and throttle cables move smooth-
ly. 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.P3-15~16
Sprocket Check that the driven sprocket tightening bolt is
not loose.P3-24
Lubrication Check for smooth operation. Lubricate if necessary. P3-37
Bolts and nuts Check the chassis and engine for loose bolts and nuts. P1-16
Lead connectors Check that the CDI magneto, CDI unit, and ignition coil
are connected tightly.P1-6
Settings Is the machine set suitably for the condition of the
racing course and weather or by taking into account the
P7-1~25
results of test runs before racing? Are inspection and
maintenance completely done?
5XE-9-30-3A 4/28/03 5:55 PM Page 14

3-36
STEERING HEAD INSPECTION AND ADJUSTMENT
INSP
ADJ
9Loosen the ring nut one turn.
9Retighten the ring nut using the ring nut
wrench.
w
Avoid over-tightening.
9Check the steering shaft by turning it lock to
lock. If there is any binding, remove the
steering shaft assembly and inspect the
steering bearings.
9Install the plain washer 5, handle crown 6,
plain washer 7, steering shaft nut 8, han-
dlebar 9, handlebar holder 0 and number
plate q.
NOTE:
9The upper handlebar holder should be
installed with the punched mark aforward.
9Insert the end of fuel breather hose winto
the hole of the number plate.
cC
First tighten the bolts on the front side of
the handlebar holder, and then tighten the
bolts on the rear side.
Ring nut wrench:
YU-33975/90890-01403
Ring nut (initial tightening):
38 Nm (3.8 m•kg, 27ft•lb)
Steering shaft nut:
145 Nm (14.5 m•kg, 105 t•lb)
Handlebar upper holder:
28 Nm (2.8 m•kg, 20 ft•lb)
Pinch bolt (handle crown):
23 Nm (2.3 m•kg, 17 ft•lb)
Number plate:
7 Nm (0.7 m•kg, 5.1 ft•lb)
Ring nut (final tightening):
7 Nm (0.7 m•kg, 5.1 ft•lb)
5XE-9-30-3B 4/16/03 10:24 AM Page 36