fuel YAMAHA YZ125LC 2002 Owner's Manual

3-39
IGNITION TIMING CHECK
INSP
ADJ
EC372012
IGNITION TIMING CHECK
1. Remove:
9Fuel tank
Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section in the CHAPTER 4.
9Spark plug
9Crankcase cover (left)
2. Attach:
9Dial gauge 1
9Spark plug hole dial stand 2
3. Rotate the magneto rotor 1until the
piston reaches top dead center (TDC).
When this happens, the needle on the dial
gauge will stop and reverse directions even
though the rotor is being turned in the same
direction.
4. Set the dial gauge to zero at TDC.
5. From TDC, rotate the rotor clockwise
until the dial gauge indicates that the
piston is at a specified distance from TDC.
6. Check:
9Ignition timing
Punch mark aon rotor should be aligned
with punch mark bon stator.
Not aligned Adjust.
Dial gauge:
YU-3097/90890-01252
Spark plug hole dial stand:
YU-1256
Ignition timing (B.T.D.C.):
0.52 mm (0.020 in)
5NY-9-30-3B 5/23/01 8:34 PM Page 42

4-1
ENGSEAT, FUEL TANK AND SIDE COVERS
EC400000
ENGINE
EC4R0000
SEAT, FUEL TANK AND SIDE COVERS
Extent of removal Order Part name Q’ty Remarks
SEAT, FUEL TANK AND SIDE
COVERS REMOVAL
Preparation for Turn the fuel cock to “OFF”.
removal Disconnect the fuel hose.
1 Seat 1
2 Air scoop (left and right) 2
3 Fitting band 1 Remove on fuel tank side.
4 Bolt (fuel tank) 2
5 Fuel tank 1
6 Side cover (left) 1
Refer to “REMOVAL POINTS”.
7 Side cover (right) 1
8 Number plate 1
1
4
Extent of removal:1Seat removal2Fuel tank removal
3Side covers removal4Number plate removal
2


 

3
4
7 Nm (0.7 m•kg, 5.1 ft•lb)
4 Nm (0.4 m•kg, 2.9 ft•lb)
4 Nm (0.4 m•kg, 2.9 ft•lb)
7 Nm (0.7 m•kg, 5.1 ft•lb)
7 Nm (0.7 m•kg, 5.1 ft•lb)
7 Nm (0.7 m•kg, 5.1 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
7 Nm (0.7 m•kg, 5.1 ft•lb)
19 Nm (1.9 m•kg, 13 ft•lb)
19 Nm (1.9 m•kg, 13 ft•lb)
5NY-9-30-4A 5/23/01 8:40 PM Page 2

4-2
ENGSEAT, FUEL TANK AND SIDE COVERS
EC4R3000
REMOVAL POINTS
EC413110
Side cover
1. Remove:
9Bolt (side cover)
9Side cover (left and right) 1
NOTE:
Draw the side cover downward to remove it
because its claws aare inserted in the air
cleaner case.
5NY-9-30-4A 5/23/01 8:40 PM Page 4

4-3
ENGEXHAUST PIPE AND SILENCER
EC4S0000
EXHAUST PIPE AND SILENCER
Extent of removal Order Part name Q’ty Remarks
EXHAUST PIPE AND
SILENCER REMOVAL
Preparation for Side cover (right) Refer to “SEAT, FUEL TANK AND
removal SIDE COVERS” section.
1 Bolt (silencer) 2
2 Silencer 1
3 Collar [D=ø10.5 mm (0.41 in)] 1
4 Collar [D=ø10.0 mm (0.39 in)] 1
5 Grommet (front) 1
6 Grommet (rear) 1
7 Tension spring 2
8 Bolt (exhaust pipe) 2
9 Exhaust pipe 1
1
Extent of removal:1Silencer removal2Exhaust pipe removal
2
12 Nm (1.2 m•kg, 8.7 ft•lb)
12 Nm (1.2 m•kg, 8.7 ft•lb)
12 Nm (1.2 m•kg, 8.7 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
7 Nm (0.7 m•kg, 5.1 ft•lb)
2
5NY-9-30-4A 5/23/01 8:40 PM Page 6

4-4
ENGRADIATOR
Extent of removal Order Part name Q’ty Remarks
RADIATOR REMOVAL
Preparation for Drain the coolant.
Refer to “COOLANT REPLACEMENT“
removal section in the CHAPTER 3.
Seat and fuel tank Refer to “SEAT, FUEL TANK AND
SIDE COVERS” section.
1 Panel 2
2 Clamp (radiator hose 1, 3) 2 Only loosening.
3 Radiator hose 2 1
4 Radiator (left) 1
5 Radiator hose 4 1
6 Radiator (right) 1
7 Radiator hose 1 1
8 Radiator hose 3 1
9 Radiator breather hose 1
EC450001
RADIATOR
Extent of removal:1Radiator removal
1
10 Nm (1.0 m•kg, 7.2 ft•lb)
1 Nm (0.1 m•kg, 0.7 ft•lb)
1 Nm (0.1 m•kg, 0.7 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
5NY-9-30-4A 5/23/01 8:40 PM Page 8

4-7
ENGCARBURETOR AND REED VALVE
EC460000
CARBURETOR AND REED VALVE
Extent of removal Order Part name Q’ty Remarks
CARBURETOR AND
REED VALVE REMOVAL
Preparation for Fuel tank Refer to “SEAT, FUEL TANK AND
removal SIDE COVERS” section.
1 Clamp (carburetor joint) 2
Loosen the screws (carburetor joint).
2 Carburetor 1
3 Carburetor joint 1
4 Reed valve assembly 1
5 Stopper (reed valve) 2
6 Reed valve 21
Extent of removal:1Carburetor removal2Reed valve removal
2
10 Nm (1.0 m•kg, 7.2 ft•lb)
1 Nm (0.1 m•kg, 0.7 ft•lb)
5NY-9-30-4A 5/23/01 8:40 PM Page 14

4-11
ENGCARBURETOR AND REED VALVE
Measurement and adjustment steps:
9Remove the drain plug.
9Connect the fuel level gauge adapter 2
and fuel level gauge 1to the float chamber.
Fuel level gauge adapter:
YM-01470/90890-01470
Fuel level gauge:
YM-1312-A/90890-01312
9Hold the fuel level gauge vertically next to
the float chamber mating surface.
9Measure the fuel level with the fuel level
gauge.
NOTE:
Keep the carburetor and fuel level gauge ver-
tically when measuring the fuel level.
9If the fuel level is not within specification, in-
spect the valve seat and needle valve.
9If either is worn, replace them both.
9If both are fine, adjust the fuel level by
bending the float tab bon the float.
9Recheck the fuel level.
EC464802
Fuel level
1. Measure:
9Fuel level a
Out of specification Adjust.
*For EUROPE
Fuel level:
9.5~10.5 mm (0.37~0.41 in)
*11.5~12.5 mm (0.45~0.49 in)
Above the float chamber
mating surface
EC464A00
Filter
1. Inspect:
9Filter 1
Damage  Replace.
NOTE:
Inspect the filter as it is assembled to the carbu-
retor. Do not remove the filter except when
replacing it.
5NY-9-30-4A 5/23/01 8:40 PM Page 22

4-17
ENGCYLINDER HEAD, CYLINDER AND PISTON
EC470000
CYLINDER HEAD, CYLINDER AND PISTONEC478000
CYLINDER HEAD AND CYLINDER
Extent of removal Order Part name Q’ty Remarks
CYLINDER HEAD AND
CYLINDER REMOVAL
Preparation for Seat and fuel tank Refer to “SEAT, FUEL TANK AND
removal SIDE COVERS” section.
Exhaust pipe and silencer Refer to ”EXHAUST PIPE AND
SILENCER” section.
Radiator hose 2 Disconnect at cylinder head side.
Bolt (radiator) Refer to “RADIATOR” section.
Radiator hose 3 Disconnect at right side radiator,
then shift the radiators forward.
1 Spark plug 1
2 Engine bracket 2
3 Nut (cylinder head) 5
Loosen each nut 1/4 turn, and remove
them after all nuts are loosened.
4 Cylinder head 1
5 Power valve housing 1
6 Push rod 1 Refer to “REMOVAL POINTS”.
7 Nut (cylinder) 4
8 Cylinder 1
Extent of removal:1Cylinder head removal2Cylinder removal
1
2
34 Nm (3.4 m•kg, 24 ft•lb)
20 Nm (2.0 m•kg, 14 ft•lb)
28 Nm (2.8 m•kg, 20 ft•lb)
5 Nm (0.5 m•kg, 3.6 ft•lb)
5 Nm (0.5 m•kg, 3.6 ft•lb)
30 Nm (3.0 m•kg, 22 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
5NY-9-30-4A 5/23/01 8:40 PM Page 34

4-53
ENGCDI MAGNETO
Extent of removal Order Part name Q’ty Remarks
CDI MAGNETO REMOVAL
Preparation for Seat and fuel tank Refer to “SEAT, FUEL TANK AND
removal SIDE COVERS” section.
Bolt [Radiator (left)] Refer to “RADIATOR” section.
Disconnect the CDI magneto lead.
1 Crankcase cover (left) 1
2 Nut (rotor) 1 Use special tool.
3 Rotor 1 Refer to “REMOVAL POINTS”.
4 Stator 1
5 Woodruff key 1
EC4L0000
CDI MAGNETO
1
Extent of removal:1CDI magneto removal



8 Nm (0.8 m•kg, 5.8 ft•lb)
33 Nm (3.3 m•kg, 24 ft•lb)
5 Nm (0.5 m•kg, 3.6 ft•lb)
5NY-9-30-4C 5/23/01 8:56 PM Page 32

4-57
ENGENGINE REMOVAL
Extent of removal Order Part name Q’ty Remarks
ENGINE REMOVAL
Preparation for
Hold the machine by placing the
removalsuitable stand under the engine.
Seat and fuel tankRefer to “SEAT, FUEL TANK AND
SIDE COVERS” section.
Carburetor Refer to “CARBURETOR AND REED
VALVE” section.
Exhaust pipe and silencer Refer to “EXHAUST PIPE AND
SILENCER” section.
Clutch cable Disconnect at engine side.
Radiator hose 2 Disconnect at cylinder head side.
Radiator hose 4 Disconnect at water pump side.
Bolt (radiator) Refer to “RADIATOR” section.
Radiator hose 3 Disconnect at right side radiator,
then shift the radiators forward.
Spark plug cap
Disconnect the CDI magneto lead.
EC4M0000
ENGINE REMOVAL
w
Support the machine securely so there is no dan-
ger of it falling over.
26 Nm (2.6 m•kg, 19 ft•lb)
34 Nm (3.4 m•kg, 24 ft•lb)
69 Nm (6.9 m•kg, 50 ft•lb)
69 Nm (6.9 m•kg, 50 ft•lb)
85 Nm (8.5 m•kg, 61 ft•lb)
60 Nm (6.0 m•kg, 43 ft•lb)
5 Nm (0.5 m•kg, 3.6 ft•lb)
5NY-9-30-4D 5/24/01 8:33 PM Page 2