2002 YAMAHA YZ250LC ignition

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.):
0.18 mm (0.007 in)
5NX-9-30-3B 6/5/01 4:06 PM Page 46

3-40
IGNITION TIMING CHECK
INSP
ADJ
7. Adjust:
9Ignition timing
Adjustment steps:
9Loosen the screws (stator) 1.
9Align the punch mark on the rotor with
punch mark on the stator 2by moving the
stator.
9Tighten the screws (stator).
Screw (stator):
8 Nm (0.8 m•kg, 5.8 ft•lb)
5NX-9-30-3B 6/5/01 4:06 PM Page 48

4-58
CDI MAGNETOENG
5. Tighten:
9Screw (stator) 1
6. Check:
9Ignition timing
Re-check the ignition timing.
3. Install:
9Plain washer 1
9Nut (rotor) 2
Use the rotor holding tool 3.
4. Adjust:
9Ignition timing
Refer to “IGNITION TIMING CHECK” sec-
tion in the CHAPTER 3. 2. Install:
9Woodruff key 1
9Rotor 2
NOTE:
9Clean the tapered portions of the crankshaft
and rotor.
9When installing the woodruff key, make sure
that its flat surface ais in parallel with the
crankshaft center line b.
9When installing the rotor, align the keyway c
of the rotor with the woodruff key.
8 Nm (0.8 m•kg, 5.8 ft•lb)
Rotor holding tool:
YU-1235/90890-01235
Ignition timing (B.T.D.C.):
0.18 mm (0.007 in)
41 Nm (4.1 m•kg, 30 ft•lb)
5NX-9-30-4C 6/5/01 4:25 PM Page 18

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

6-3
IGNITION SYSTEMELEC
EC622001
SPARK GAP TEST
1. Disconnect the spark plug cap from spark
plug.
2. Connect the dynamic spark tester 1(igni-
tion checker 2) as shown.
9Spark plug cap 3
9Spark plug 4
AFor USA and CDN
BExcept for USA and CDN
3. Kick the kick starter.
4. Check the ignition spark gap.
5. Start engine, and increase spark gap until
misfire occurs. (for USA and CDN only)
EC624000
COUPLERS AND LEADS CONNECTION
INSPECTION
1. Check:
9Couplers and leads connection
Rust/ Dust/ Looseness/Short-circuit 
Repair or replace.
EC625002
“ENGINE STOP” BUTTON INSPECTION
1. Inspect:
9“ENGINE STOP” button conduct
Not continuous while being pushed Replace.
Continuous while being freed Replace.
Minimum spark gap:
6.0 mm (0.24 in)
Tester (+) leadBlack/White lead 1
Tester (–) lead
Black lead 2
B/W B
12
PUSH IN
FREE
Tester selec-
tor position
Ω× 1
å å
B
5NX-9-30-6 6/5/01 4:44 PM Page 8

6-4
IGNITION SYSTEMELEC
EC626002
IGNITION COIL INSPECTION
1. Inspect:
9Primary coil resistance
Out of specification Replace.
2. Inspect:
9Secondary coil resistance
Out of specification Replace.
NOTE:
When inspecting the secondary coil resistance,
remove the spark plug cap.
EC627011
CDI MAGNETO INSPECTION
1. Inspect:
9Pick-up coil resistance
Out of specification Replace.
Tester (+) leadOrange lead 1
Tester (–) lead
Black lead 2
Tester (+) leadSpark plug lead 1
Tester (–) lead
Orange lead 2
Primary coil Tester selector
resistance position
0.20~0.30Ωat
Ω× 1
20°C (68°F)
Secondary coil Tester selector
resistance position
9.5~14.3kΩat
kΩ× 1
20°C (68°F)
Tester (+) leadWhite/Red lead 1
Tester (–) lead
White/Blue lead 2
Pick–up coil Tester selector
resistance position
248~372Ωat
Ω× 100
20°C (68°F)
5NX-9-30-6 6/5/01 4:44 PM Page 10

6-5
IGNITION SYSTEMELEC
2. Inspect:
9Source coil 1 resistance
Out of specification Replace.
3. Inspect:
9Source coil 2 resistance
Out of specification Replace.
EC628000
CDI UNIT INSPECTION
Check all electrical components. If no fault is
found, replace the CDI unit. Then check the
electrical components again.
Tester (+) leadBlack/Red lead 1
Tester (–) lead
Blacklead 2
Source coil 1 Tester selector
resistance position
720~1,080Ωat
Ω× 100
20°C (68°F)
Tester (+) leadGreen/Blue lead 1
Tester (–) lead
Green/White lead 2
Source coil 2 Tester selector
resistance position
44~66Ωat
Ω× 10
20°C (68°F)
5NX-9-30-6 6/5/01 4:44 PM Page 12