2002 YAMAHA YZ250LC engine oil

4-65
CRANKCASE AND CRANKSHAFTENG
Extent of removal Order Part name Q’ty Remarks
CRANKCASE AND CRANKSHAFT
REMOVAL
Preparation for Engine Refer to “ENGINE REMOVAL”section.
removal Piston Refer to “
CYLINDER HEAD, CYLINDER
AND PISTON
” section.
Primary drive gear
Kick idle gearRefer to “
KICK AXLE, SHIFT SHAFT AND
Stopper leverPRIMARY DRIVE GEAR”section.
Rotor and stator Refer to “CDI MAGNETO” section.
1 Segment 1 Refer to “REMOVAL POINTS”.
2 Bolt [L=50 mm (1.97 in)] 7
3 Bolt [L=60 mm (2.36 in)] 1
4 Bolt [L=70 mm (2.76 in)] 3
5 Holder 2
6 Crankcase (right) 1 Use special tool.
7 Crankcase (left) 1 Refer to “REMOVAL POINTS”.
8 Crankshaft 1 Use special tool.
Refer to “REMOVAL POINTS”.
9 Oil seal 2
10 Bearing 2 Refer to “REMOVAL POINTS”.




EC4N0000
12
3
Extent of removal:1Crankcase separation2Crankshaft removal
3Crankshaft bearing removal



10 Nm (1.0 m•kg, 7.2 ft•lb)30 Nm (3.0 m•kg, 22 ft•lb)
14 Nm (1.4 m•kg, 10 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
5NX-9-30-4C 6/5/01 4:25 PM Page 32

4-71
CRANKCASE AND CRANKSHAFTENG
8. Tighten:
9Segment 1
9Bolt (segment) 2
NOTE:
9When installing the segment onto the shift cam
3, align the punch mark awith the dowel pin
b.
9Turn the segment clockwise until it stops and
tighten the bolt.
30 Nm (3.0 m•kg, 22 ft•lb)
7. Install:
9Tension spring 1
9Holder 2
9Bolt (holder) 3
NOTE:
Install the holder so that it contacts the projec-
tion aon the crankcase (right).
10 Nm (1.0 m•kg, 7.2 ft•lb)
9. Remove:
9Sealant
Forced out on the cylinder mating surface.
10. Apply:
9Engine oil
To the crank pin, bearing, oil delivery hole
and connecting rod big end washer.
11. Check:
9Crankshaft and transmission operation
Unsmooth operation
Repair.
5NX-9-30-4C 6/5/01 4:26 PM Page 44

5-1
CHASFRONT WHEEL AND REAR WHEEL
Extent of removal Order Part name Q’ty Remarks
FRONT WHEEL REMOVAL
Preparation for
Hold the machine by placing the
removalsuitable stand under the engine.
1 Hose cover 1
2 Bolt (brake hose holder) 2 Only loosening.
3 Bolt (axle holder) 4 Only loosening.
4 Nut (front wheel axle) 1
5 Front wheel axle 1
6 Front wheel 1
7 Collar 2
8 Oil seal 2
9 Bearing 2 Refer to “REMOVAL POINTS”.
10 Brake disk 1
EC500000
CHASSISEC590000
FRONT WHEEL AND REAR WHEELEC598000
FRONT WHEEL
2
13
3
Extent of removal:1Front wheel removal2Wheel bearing removal3Brake disc removal
w
Support the machine securely so there is no dan-
ger of it falling over.
5
23 Nm (2.3 m•kg, 17 ft•lb)
23 Nm (2.3 m•kg, 17 ft•lb)
105 Nm (10.5 m•kg, 75 ft•lb)
16 Nm (1.6 m•kg, 11 ft•lb)
7 Nm (0.7 m•kg, 5.1 ft•lb)12 Nm (1.2 m•kg, 8.7 ft•lb)
10 Nm (1.0 m•kg, 7.2 ft•lb)
5NX-9-30-5A 6/7/01 2:00 PM Page 2

5-2
CHASFRONT WHEEL AND REAR WHEEL
EC598100
REAR WHEEL
Extent of removal:1Rear wheel removal2Wheel bearing removal3Brake disc removal
Extent of removal Order Part name Q’ty Remarks
REAR WHEEL REMOVAL
Preparation for
Hold the machine by placing the
removalsuitable stand under the engine.
1 Nut (rear wheel axle) 1
2 Rear wheel axle 1
3 Chain puller 2
4 Rear wheel 1 Refer to “REMOVAL POINTS”.
5 Collar 2
6 Driven sprocket 1
7 Oil seal 2
8 Circlip 1
9 Bearing 2 Refer to “REMOVAL POINTS”.
10 Brake disk 1
2
13
3
w
Support the machine securely so there is no dan-
ger of it falling over.
125 Nm (12.5 m•kg, 90 ft•lb)
14 Nm (1.4 m•kg, 10 ft•lb)
42 Nm (4.2 m•kg, 30 ft•lb)
5NX-9-30-5A 6/7/01 2:00 PM Page 4

6-1
ELECTRICAL COMPONENTS AND WIRING DIAGRAMELEC
EC600000
ELECTRICAL
EC610000
ELECTRICAL COMPONENTS AND WIRING DIAGRAM
EC611000
ELECTRICAL COMPONENTS
1CDI unit
2“ENGINE STOP” button
3Ignition coil
4TPS (throttle position sensor)
5Solenoid valve
6CDI magneto
7Spark plug
EC612000
WIRING DIAGRAM
COLOR CODE
B...................Black
L ...................Blue
O ..................Orange
R ..................Red
Y...................Yellow
B/L................Black/Blue
B/R ...............Black/Red
B/W ..............Black/White
G/L ..............Green/Blue
G/W ..............Green/White
W/L...............White/Blue
W/R ..............White/Red
6
L
Y
B/LYL
B/LY LL
Y
B
B/W
B B/W
B
R
BB
RR
RR
R
B
B/R
G/L
G/W
W/R
W/L W/L B/R
G/L
W/R
B G/W G/L B/R W/L
G/W B W/R
O
B G/W G/L
Y B/L
L
W/R
W/L
B
R
B/R
B/W
O G/L
B/L
L
W/L
B
R
B/R
B/WG/W
Y
W/R
OB/L
5NX-9-30-6 6/5/01 4:44 PM Page 2

6-2
IGNITION SYSTEMELEC
EC620000
IGNITION SYSTEM
EC621002
INSPECTION STEPS
Use the following steps for checking the possibility of the malfunctioning engine being attributable to
ignition system failure and for checking the spark plug which will not spark.
*Clean or replace
spark plug.
Primary coil
Secondary coil
Repair or replace.
Spark
Check entire ignition
system for connection.
Spark gap test
No good
No good
No good
No good
No good
No good No Spark
Check “ENGINE STOP”
button.
Pick-up coil
Source coil
Check ignition coil.
Check CDI magneto.
Replace CDI unit.
Replace.
Replace.
Replace.
Replace.
Replace.
*marked: Only when the ignition checker is used.
NOTE:
9Remove the following parts before inspection.
1) Seat
2) Fuel tank
9Use the following special tools in this inspection.
Dynamic spark tester:
YM-34487
Ignition checker:
90890-06754Pocket tester:
YU-3112-C/90890-03112
OK
OK
OK
OK
5NX-9-30-6 6/5/01 4:44 PM Page 4

6-8
TPS (THROTTLE POSITION SENSOR) SYSTEMELEC
Check entire ignition
system for connection.Repair or replace.
OK
OKTPS coil
No goodReplace.Check TPS.
OKSource coil
No goodReplace.*Check CDI magneto.
TPS input
voltageNo goodReplace.Check CDI unit.
No good
EC690000
TPS (THROTTLE POSITION SENSOR) SYSTEM
EC691001
INSPECTION STEPS
If the TPS will not operate, use the following inspection steps.
*marked: Refer to “IGNITION SYSTEM” section.
NOTE:
9Remove the following parts before inspection.
1) Seat
2) Fuel tank
9Use the following special tools in this inspection.
Inductive tachometer:
YU-8036-B
Engine tachometer:
90890-03113Pocket tester:
YU-3112-C/90890-03112
5NX-9-30-6 6/5/01 4:44 PM Page 20

6-9
TPS (THROTTLE POSITION SENSOR) SYSTEMELEC
L
Y
B1
21
2
EC624000
COUPLERS AND LEADS CONNECTION
INSPECTION
1. Check:
9Couplers and leads connection
Rust/ Dust/ Looseness/Short-circuit 
Repair or replace.
EC692000
TPS COIL INSPECTION
1. Remove:
9Carburetor
9Mixing chamber top
Refer to “CARBURETOR AND REED
VALVE” section in the CHAPTER 4.
2. Inspect:
9TPS coil resistance
Out of specification Replace.
Tester (+) leadBluelead 1
Tester (–) lead
Blacklead 2
TPS coil Tester selector
resistance position
4~6kΩat
kΩ×1
20°C (68°F)
EC69A000
HANDLING NOTE
cC
Do not loosen the screws {TPS (throttle
position sensor)} except when changing
the TPS (throttle position sensor) due to
failure because it will cause a drop in
engine performance.
5NX-9-30-6 6/5/01 4:44 PM Page 24