2014 YAMAHA YZ250F Owners Manual

IGNITION SYSTEM
8-3
EAS1SM1323
1. Crankshaft position sensor
2. AC magneto
3. Rectifier/regulator
4. Joint connector
5. Condenser
7. Engine stop switch
9. ECU
10.Ignition coil
11.Spark plug

IGNITION SYSTEM
8-4
TROUBLESHOOTING
The ignition system fails to operate (no spark or intermittent spark).
TIP
Before troubleshooting, remove the following part(s):
1. Side cover (left/right)
2. Seat
3. Fuel tank
4. Air scoop (left/right)
5. Air filter case cover
1. Check the ignition system wire har-
ness connections.NG 
Reconnect.
OK 
2. Check the spark plug.
Refer to “CHECKING THE SPARK
PLUG” on page 3-35.NG 
Correct or replace the spark plug.
OK 
3. Check the ignition spark gap.
Refer to “CHECKING THE IGNI-
TION SPARK GAP” on page 8-41.OK 
The ignition system circuit is OK.
NG 
4. Check the ignition coil.
Refer to “CHECKING THE IGNI-
TION COIL” on page 8-41.NG 
Replace the ignition coil.
OK 
5. Check the engine stop switch.
Refer to “CHECKING THE
SWITCHES” on page 8-38.NG 
Replace the engine stop switch.
OK 
6. Check the crankshaft position sen-
sor.
Refer to “CHECKING THE CRANK-
SHAFT POSITION SENSOR” on
page 8-42.NG 
Replace the crankshaft position sensor.
OK 
7. Check the stator coil.
Refer to “CHECKING THE STA-
TOR COIL” on page 8-43.NG 
Replace the stator coil.
OK 

IGNITION SYSTEM
8-5
8. Check the ignition system wire har-
ness.
Refer to “CIRCUIT DIAGRAM” on
page 8-2.NG 
Repair or replace the wire harness.
OK 
Replace the ECU.

CHARGING SYSTEM
8-6
EAS27200
CHARGING SYSTEM
EAS1SM1324CIRCUIT DIAGRAM
B/LGy
BR
A
A
AA
B
RR R R R R R
B
B
B
RR
R
Lg
LgB/WB/Y
B/YB
B
BP
PP
Sb
B/LP/B
P/B
YL
YL
L
G/WBr/W
G/WBr/W
B/LB/L
B/L
B/L
B/R
B/R
R/B
R/B
O
OROR
OR
R
R
SbB
GyR
B/W
P L B/L
B/L Gy B/L B/L B/L B/L B/L
LL
PP
BBBB
PP
Sb
RB
B/RR
RB
B/Y PSb
BB
RR/B
LYB/L
B/W RLg
B/LBr/W
B/L P/B LB/LG/W
BB/Y
BB/L B/L B/L B/L B/L B/LBBBBRR
PPPL L LRR RR R
B
O P
Gy
R
B/Y Sb
P/B
R/B Lg B/RG/WBr/WB/L L Y
RB
B/L
Gy
R
O
O
R(BLACK) (BLACK)
B/W
4
1
3
2
5
67
8
10
9
1211
13
1415
16
17

CHARGING SYSTEM
8-7
EAS1SM1325
2. AC magneto
3. Rectifier/regulator
4. Joint connector
5. Condenser

CHARGING SYSTEM
8-8
TROUBLE SHOOTING
The condenser is not being charged.
TIP
Before troubleshooting, remove the following part (s):
1. Seat
2. Air scoop (left)
1. Check the entire charging system’s
wiring.NG 
Reconnect.
OK 
2. Check the rectifier/regulator.
Refer to “CHECKING THE RECTI-
FIER/REGULATOR” on page 8-43.NG 
Replace the rectifier/regulator.
OK 
3. Check the stator coil.
Refer to “CHECKING THE STA-
TOR COIL” on page 8-43.NG 
Replace the stator coil.
OK 
4. Check the charging system wire
harness.
Refer to “CIRCUIT DIAGRAM” on
page 8-6.NG 
Repair or replace the wire harness.
OK 
Replace the condenser.

CHARGING SYSTEM
8-9
EAS1SM1326

FUEL INJECTION SYSTEM
8-10
FUEL INJECTION SYSTEM
EAS1SM1327CIRCUIT DIAGRAM
B/LGy
BR
A
A
AA
B
RR R R R R R
B
B
B
RR
R
Lg
LgB/WB/Y
B/YB
B
BP
PP
Sb
B/LP/B
P/B
YL
YL
L
G/WBr/W
G/WBr/W
B/LB/L
B/L
B/L
B/R
B/R
R/B
R/B
O
OROR
OR
R
R
SbB
GyR
B/W
P L B/L
B/L Gy B/L B/L B/L B/L B/L
LL
PP
BBBB
PP
Sb
RB
B/RR
RB
B/Y PSb
BB
RR/B
LYB/L
B/W RLg
B/LBr/W
B/L P/B LB/LG/W
BB/Y
BB/L B/L B/L B/L B/L B/LBBBBRR
PPPL L LRR RR R
B
O P
Gy
R
B/Y Sb
P/B
R/B Lg B/RG/WBr/WB/L L Y
RB
B/L
Gy
R
O
O
R(BLACK) (BLACK)
B/W
4
1
3
2
5
67
8
10
9
1211
13
1415
16
17