YAMAHA YZ250F 2014 Owners Manual

FUEL PUMP SYSTEM
8-35
EAS1SM1333

ELECTRICAL COMPONENTS
8-36 ELECTRICAL COMPONENTS
EAS1SM1334
9
10
1
2
3
4
56
7
8

ELECTRICAL COMPONENTS
8-37
EAS1SM1335
1. Rectifier/regulator
2. Intake air pressure sensor
3. Throttle position sensor
4. Injector
5. Intake air temperature sensor
6. ECU
7. Ignition coil
8. Condenser
9. Neutral switch
10.Coolant temperature sensor

ELECTRICAL COMPONENTS
8-38
CHECKING THE SWITCHES
B/Y P
Sb
21

ELECTRICAL COMPONENTS
8-39
1. Engine stop switch
2. Neutral switch

ELECTRICAL COMPONENTS
8-40
Check each switch for continuity with the pocket tester. If the continuity reading is incorrect, check
the wiring connections and if necessary, replace the switch.
ECA14370
NOTICE
Never insert the tester probes into the coupler terminal slots “1”. Always insert the probes
from the opposite end of the coupler, taking care not to loosen or damage the leads.
TIP
• Before checking for continuity, set the pocket tester range to “ 1” to make a “0” adjustment.
• When checking for continuity, switch back and forth between the switch positions a few times.
Terminal connections of the switch are shown in the terminal connection diagram below.
The switch positions “a” are shown in the far left column and the switch lead colors are shown in the
top row in the switch illustration.
TIP
“ ” indicates continuity between switch terminals (i.e., a closed circuit at each switch posi-
tion).
The example illustration below shows that:
There is continuity between red and brown when the switch is “ON”.Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
a

ELECTRICAL COMPONENTS
8-41
EAS1SM1336CHECKING THE IGNITION SPARK GAP
1. Check:
• Ignition spark gap
Out of specification  Perform the ignition
system troubleshooting.
Refer to “TROUBLESHOOTING” on page 8-
4.
TIP
If the ignition spark gap is within specification,
the ignition system circuit is operating normally.
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a. Remove the spark plug cap from the spark
plug.
b. Connect the ignition checker “1”.
c. Crank the engine, and measure the ignition
spark gap “a”.
d. Crank the engine, and gradually increase
the spark gap until a misfire occurs.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲EAS1SM1337CHECKING THE SPARK PLUG CAP
1. Remove:
• Spark plug cap
(from the spark plug lead)
2. Check:
• Spark plug cap resistance
Out of specification  Replace.
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a. Connect the pocket tester ( 1k) to the
spark plug cap.
b. Measure the spark plug cap resistance.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲EAS1SM1338CHECKING THE IGNITION COIL
1. Disconnect:
• Ignition coil terminal
(from the sub wire harness)
• Spark plug cap
(from the ignition coil)
2. Check:
• Primary coil resistance
Out of specification  Replace.
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Connect the pocket tester ( 1) to the igni-
tion coil. Minimum ignition spark gap
6.0 mm (0.24 in)
Ignition checker
90890-06754
Oppama pet-4000 spark checker
YM-34487
2. Spark plug cap
Spark plug cap resistance
10 k
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
Primary coil resistance
2.16–2.64 
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
• Positive tester probe 
Ignition coil terminal 1 “1”
• Negative tester probe 
Ignition coil terminal 2 “2”

ELECTRICAL COMPONENTS
8-42
b. Measure the primary coil resistance.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
3. Check:
• Secondary coil resistance
Out of specification  Replace.
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Connect the pocket tester ( 1k) to the ig-
nition coil.
b. Measure the secondary coil resistance.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲EAS1SM1339
CHECKING THE CRANKSHAFT POSITION
SENSOR
1. Disconnect:
• Crankshaft position sensor coupler
(from the wire harness)
2. Check:
• Crankshaft position sensor resistance
Out of specification  Replace.
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Connect the pocket tester ( 100) to the
crankshaft position sensor coupler.
b. Measure the crankshaft position sensor re-
sistance.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲EAS1SM1340
Secondary coil resistance
8.64–12.96 k
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
• Positive tester probe 
Ignition coil terminal 1 “1”
• Negative tester probe 
Spark plug lead “2”
Crankshaft position sensor resis-
tance
228–342 
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
• Positive tester probe 
Gray “1”
• Negative tester probe 
Black “2”
12
Gy B

ELECTRICAL COMPONENTS
8-43
CHECKING THE ECU
1. Check:
• Mounted condition of ECU.
Improperly mounted  Remount.
TIP
• The lean angle sensor is built into the ECU.
• The lean angle sensor stops the engine in
case of a turnover.
• To ensure that the lean angle sensor operates
correctly, do not change the installed condi-
tion of the ECU.
EAS1SM1341CHECKING THE STATOR COIL
1. Disconnect:
• Stator coil coupler
(from the wire harness)
2. Check:
• Stator coil resistance
Out of specification  Replace.
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Connect the pocket tester ( 1) to the sta-
tor coil coupler.
b. Measure the stator coil resistance.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲EAS1SM1342
CHECKING THE RECTIFIER/REGULATOR
1. Check:
• Rectifier/regulator output voltage
Out of specification  Replace.
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Set the digital tachometer to the ignition coil.
b. Connect the pocket tester (20 VDC) to the
rectifier/regulator coupler.
c. Start the engine and let it run at about 5000
r/min.
d. Measure the output voltage.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲EAS1SM1343
Stator coil resistance
0.624–0.936 
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
• Positive tester probe 
White “1”
• Negative tester probe 
White “2”
12
Output voltage
14 V or more at 5000 r/min
Digital tachometer
90890-06760
YU-39951-B
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
• Positive tester probe 
Red “1”
• Negative tester probe 
Black “2”
21
B
WWR

ELECTRICAL COMPONENTS
8-44
CHECKING THE COOLANT TEMPERATURE
SENSOR
1. Remove:
• Coolant temperature sensor
EWA14130
WARNING
• Handle the coolant temperature sensor
with special care.
• Never subject the coolant temperature
sensor to strong shocks. If the coolant
temperature sensor is dropped, replace it.
2. Check:
• Coolant temperature sensor resistance
Out of specification  Replace.
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Connect the pocket tester ( 1k/100) to
the coolant temperature sensor.
b. Immerse the coolant temperature sensor in
a container filled with coolant.
TIP
Make sure the coolant temperature sensor ter-
minals do not get wet.c. Place a thermometer in the coolant.
d. Slowly heat the coolant, and then let it cool
to the specified temperature indicated in the
table.
e. Check the coolant temperature sensor for
continuity at the temperatures indicated in
the table.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲EAS1SM1344CHECKING THE THROTTLE POSITION
SENSOR
1. Remove:
• Throttle position sensor
(from the throttle body)
EWA1DX1009
WARNING
• Handle the throttle position sensor with
special care.
• Never subject the throttle position sensor
to strong shocks. If the throttle position
sensor is dropped, replace it. Coolant temperature sensor re-
sistance
2.51–2.78 k at 20 °C (68 °F)
210–221  at 100 °C (212 °F)
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
• Positive tester probe 
Green/White “1”
• Negative tester probe 
Black/Blue “2”12
G/W B/L
B/L G/W