2008 YAMAHA WR 250F ignition

3-27
ELECTRICAL
ELECTRICAL
CHECKING THE SPARK PLUG
1. Remove:• Spark plug
2. Inspect:
• Electrode "1"Wear/damage →Replace.
• Insulator color "2"
Normal condition is a medium to
light tan color.
Distinctly different color →Check
the engine condition.
When the engine runs for many hours
at low speeds, the spark plug insula-
tor will become sooty, even if the en-
gine and carburetor are in good
operating condition.
3. Measure: • Plug gap "a"Use a wire gauge or thickness
gauge.
Out of specification →Regap.
4. Clean the plug with a spark plug cleaner if necessary.
5. Tighten: • Spark plug
• Before installing a spark plug, clean the gasket surface and plug sur-
face.
• Finger-tighten "a" the spark plug before torquing to specification "b".
CHECKING THE IGNITION TIMING
1. Remove:• Timing mark accessing screw "1"
2. Attach: • Timing light
• Inductive tachometerTo the ignition coil lead (orange
lead"1").
3. Adjust: • Engine idling speedRefer to "ADJUSTING THE EN-
GINE IDLING SPEED" section.
4. Check: • Ignition timingVisually check the stationary
pointer "a" is within the firing
range "b" on the rotor.
Incorrect firing range →Check ro-
tor and pickup assembly.
5. Install: • Timing mark accessing screw
CHECKING AND CHARGING THE
BATTERY
Batteries generate explosive hy-
drogen gas and contain electrolyte
which is made of poisonous and
highly caustic sulfuric acid. There-
fore, always follow these preven-
tive measures:
• Wear protective eye gear when handling or working near batter-
ies. • Charge batteries
in a well-venti-
lated area.
• Keep batteries away from fire, sparks or open flames (e.g.,
welding equipment, lighted ciga-
rettes).
• DO NOT SMOKE when charging
or handling batteries.
• KEEP BATTERIES AND ELEC- TROLYTE OUT OF REACH OF
CHILDREN.
• Avoid bodily contact with elec- trolyte as it can cause severe
burns or permanent eye injury.
FIRST AID IN CASE OF BODILY
CONTACT:
EXTERNAL
• Skin — Wash with water.
• Eyes — Flush with water for 15
minutes and get immediate med-
ical attention.
INTERNAL
• Drink large quantities of water or milk followed with milk of magne-
sia, beaten egg or vegetable oil.
Get immediate medical attention.
Charging time, charging amperage
and charging voltage for an MF
battery are different from those of
conventional batteries. The MF
battery should be charged as ex-
plained in the charging method il-
lustrations. If the battery is
overcharged, the electrolyte level
will drop considerably. Therefore,
take special care when charging
the battery.
Since MF batteries are sealed, it is
not possible to check the charge state
of the battery by measuring the spe-
cific gravity of the electrolyte. There-
fore, the charge of the battery has to
be checked by measuring the voltage
at the battery terminals.
1. Remove:• Seat
2. Disconnect:
• Battery leads(from the battery terminals)
First, disconnect the negative bat-
tery lead "1", and then the positive
battery lead "2".
Spark plug gap: 0.7–0.8 mm (0.028–
0.031 in)
Spark plug: 13 Nm (1.3 m•kg, 9.4
ft•lb)
Timing light:
YM-33277-A/90890-
03141

5-53
ENGINE REMOVAL
ENGINE REMOVAL
REMOVING THE ENGINEOrder Part name Q'ty Remarks Hold the machine by placing the suitable stand
under the frame. Refer to "HANDLING NOTE".
Drain the engine oil. Refer to "CHANGING THE ENGINE OIL"
section in the CHAPTER 3.
Seat and fuel tank Refer to "REMOVING THE SEAT, FUEL
TANK AND SIDE COVERS" section in the
CHAPTER 3.
Carburetor Refer to "CARBURETOR" section.
Exhaust pipe and silencer Refer to "REMOVING THE EXHAUST PIPE
AND SILENCER" section in the CHAPTER 3.
Air cut-off valve assembly Refer to "AIR INDUCTION SYSTEM" section.
Clutch cable Disconnect at the engine side.
Radiator Refer to "RADIATOR" section.
Shift pedal Refer to "AC MAGNETO AND STARTER
CLUTCH" section.
Cylinder head breather hose Refer to "CAMSHAFTS" section.
Oil hose and oil tank breather ho seRefer to "OIL PUMP" section.
Ignition coil

7-1
ELECTRICAL COMPONENTS AND WIRING DIAGRAM
ELECTRICAL
ELECTRICAL COMPONENTS AND WIRING DIAGRAM
ELECTRICAL COMPONENTS1. Headlight
2. Multi-function display
3. Engine stop switch
4. Clutch switch
5. Diode
6. Starter relay diode
7. Throttle position sensor
8. Starter relay
9. Fuse
10. Starting circuit cut-off relay
11. CDI unit 12. Taillight
13. Neutral switch
14. Starter motor
15. AC magneto
16. Rectifier/regulator
17. Ignition coil
18. Spark plug
19. Start switch
20. Main switch
21. Speed sensor
22. Battery

7-2
ELECTRICAL COMPONENTS AND WIRING DIAGRAM
WIRING DIAGRAM
1. Headlight
2. Multi-function display
3. Engine stop switch
4. Clutch switch
5. Diode
6. Starter relay diode
7. Throttle position sensor
8. Starter relay
9. Fuse
10. Starting circuit cut-off relay
11. CDI unit
12. Taillight
13. Neutral switch
14. Starter motor
15. AC magneto
16. Rectifier/regulator
17. Ignition coil
18. Spark plug
19. Start switch
20. Main switch
21. Speed sensor
22. Battery
*1: For USA
*2: Except for USACOLOR CODE
BBlack
Br Brown
Ch Chocolate
Dg Dark green
GGreen
Gy Gray
LBlue
O Orange
RRed
Sb Sky blue
WWhite
YYellow
B/L Black/Blue
B/W Black/White
L/B Blue/Black
L/R Blue/Red
L/Y Blue/Yellow
L/W Blue/White
R/B Red/Black
R/W Red/White


7

7-3
IGNITION SYSTEM
IGNITION SYSTEM
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.
*1 marked: Refer to "CHECKING TH E FUSE" section in the CHAPTER 3.
*2 marked: Refer to "CHECKING AND CHARGIN G THE BATTERY" section in the CHAPTER 3.
*3 marked: Only when the ignition checker is used.
• Remove the following parts before inspection.
1. Seat
2. Fuel tank
• Use the following special tools in this inspection.
*1 Check fuse. No good→Replace fuse and check wire harness.
OK ↓
*2 Check battery. No good→Recharge or replace.
OK ↓
Spark gap test Spark→ *3 Clean or replace spark plug.
No spark ↓
Check entire ignition system for connection.
(couplers, leads and ignition coil) No good
→
Repair or replace.
OK ↓
Check engine stop switch. No good→Replace.
OK ↓
Check main switch. No good→Replace.
OK ↓
Check ignition coil. (primary coil and secondary
coil) No good
→
Replace.
OK ↓
Check AC magneto. (pickup coil) No good→Replace.
OK ↓
Check neutral switch. No good→Repair or replace.
OK ↓
Replace CDI unit.
Dynamic spark tester: YM-34487
Ignition checker: 90890-06754
Pocket tester: YU-3112-C/90890-03112

7-4
IGNITION SYSTEM
SPARK GAP TEST
1. Disconnect the ignition coil from spark plug.
2. Remove the ignition coil cap.
3. Connect the dynamic spark tester "1" (ignition ch ecker "2") as
shown.
• Ignition coil "3"
• Spark plug "4"
A. For USA and CDN
B. Except for USA and CDN
4. Kick the kickstarter crank.
5. Check the ignition spark gap.
6. Start engine, and increase spark gap until misfire occurs. (for USA
and CDN only)
CHECKING THE COUPLERS,
LEADS AND IGNITION COIL
CONNECTION
1. Check: • Couplers and leads connection
Rust/dust/looseness/short-circuit
→ Repair or replace.
• Ignition coil and spark plug as
they are fitted
Push in the ignition coil until it
closely contacts the spark plug
hole in the cylinder head cover.
CHECKING THE ENGINE STOP
SWITCH
1. Inspect: • Engine stop switch conduction Not conductive while it is pushed
→
Replace.
Conductive while it is freed →Re-
place.
Set the tester selection position to " Ω
× 1".
2. Inspect: • Rubber part "a"
Tears/damage → Replace.
CHECKING THE MAIN SWITCH
1. Inspect: • Main switch conduction
Not conductive while the main switch
is moved to "ON" →Replace.
Conductive while the main switch is
moved to "OFF" →Replace.
Set the tester selection position to
"Ω×1".
2. Inspect:
• Main switch indicator lightUse 12 V battery.
Indicator light does not come on →
Replace.
3. Inspect:
• Rubber part "a"Tears/damage →Replace.
CHECKING THE IGNITION COIL
1. Remove the ignition coil cap.
2. Inspect: • Primary coil resistance
Out of specification →Replace.
3. Inspect: • Secondary coil resistanceOut of specification →Replace.
Minimum spark gap:
6.0 mm (0.24 in)
Tester (+) lead →Black lead "1"
Tester (-) lead →Black lead "2"Result
Conductive (while the
engine stop switch is
pushed)
Tester (+) lead →Red lead "1"
Tester (-) lead →Brown lead "2"
Result Conductive (while the
main switch is moved
to "ON")
Battery (+) lead →Red/Black lead
"1"
Battery (-) lead →Black lead "2"
Tester (+) lead →Orange lead "1"
Tester (-) lead →Black lead "2"
Primary
coil resis-
tance Tester se-
lector posi-
tion
0.08–0.10
Ω at 20 °C (68 °F) Ω × 1
Tester (+) lead →Orange lead "1"
Tester (-) lead →Spark plug termi-
nal "2"

7-5
ELECTRIC STARTING SYSTEM
4. Inspect:• Sealed portion of ignition coil "a"
• Spark plug terminal pin "b"
• Threaded portion of spark plug "c"Wear →Replace.
CHECKING THE AC MAGNETO
1. Inspect: • Pickup coil resistanceOut of specification →Replace. CHECKING THE NEUTRAL
SWITCH
1. Inspect:
• Neutral switch conduction
Not conductive while it is in neutral →
Replace.
Conductive while it is engaged →Re-
place.Set the tester selection position to " Ω
× 1".
CHECKING THE CDI UNIT
Check all electrical components. If no
fault is found, replace the CDI unit.
Then check the electrical compo-
nents again.
ELECTRIC STARTING
SYSTEM
STARTING CIRCUIT CUT-OFF
SYSTEM OPERATION
If the main switch is set to "ON", the
starter motor can only operate if at
least one of the following conditions is
met:
• The transmission is in neutral (the neutral switch is closed).
• The clutch lever is pulled to the han- dlebar (the clutch switch is closed).
The starting circuit cut-off relay pre-
vents the starter motor from operating
when neither of these conditions has
been met. In this instance, the start-
ing circuit cut-off relay is open so cur-
rent cannot reach the starter motor.
When at least one of the above con-
ditions has been met the starting cir-
cuit cut-off relay is closed and the
engine can be started by pressing the
start switch.
WHEN THE TRANSMISSION IS IN
NEUTRAL
WHEN THE CLUTCH LEVER IS
PULLED TO THE HANDLEBAR 1. Battery
2. Main fuse
3. Main switch
4. Starting circuit cut-off relay
5. Start switch
6. Diode
7. Clutch switch
8. Neutral switch
9. Starter relay
10. Starter motor
Secondary
coil resis- tance Tester se-
lector posi- tion
4.6–6.8
k Ωat 20 °C
(68 °F) k
Ω × 1
Tester (+) lead →Red lead "1"
Tester (-) lead →White lead "2"
Pickup coil resistance Tester se-
lector posi- tion
248–372 Ω
at 20 °C (68
°F) Ω × 100
Tester (+) lead
→Sky blue lead "1"
Tester (-) lead →Ground "2"
Result Conductive (while gear
is in neutral)

7-15
THROTTLE POSITION SENSOR SYSTEM
THROTTLE POSITION SENSOR SYSTEM
INSPECTION STEPS
If the throttle position sensor will not operate, use the following inspection steps.
Use the following special tools in this inspection.
Check entire ignition system for connection. No good →Repair or replace.
OK ↓
Check throttle position sensor.(Throttle position
sensor coil) No good
→
Replace.
OK ↓
Check CDI unit.(Throttle position sensor input
voltage) No good
→
Replace.
Pocket tester:
YU-3112-C/90890-03112