2017 YAMAHA WR 250F air filter

ELECTRICAL COMPONENTS
9-80
EAS2GBB401CHECKING THE THROTTLE POSITION
SENSOR INPUT VOLTAGE
1. Check:
• Throttle position sensor input voltage
Out of specification  Replace the ECU.
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a. Connect the test harness S-pressure sensor
(3P) to the throttle position sensor coupler
and the wire harness.
b. Connect the pocket tester (20 VDC) to the
test harness S-pressure sensor (3P).
c. Start the engine.
d. Measure the throttle position sensor input
voltage.
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EAS2GBB402CHECKING THE INTAKE AIR PRESSURE
SENSOR
1. Check:
• Intake air pressure sensor output voltage
Out of specification  Replace.
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a. Connect the pocket tester (20 VDC) to the
intake air pressure sensor coupler (wire har-
ness side).
b. Start the engine.
c. Measure the intake air pressure sensor out-
put voltage.
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EAS2GBB403CHECKING THE INTAKE AIR TEMPERA-
TURE SENSOR
1. Remove:
• Intake air temperature sensor
(from the air filter case)
EWA
WARNING
• Handle the intake air temperature sensor
with special care.
• Never subject the intake air temperature
sensor to strong shocks. If the intake air
temperature sensor is dropped, replace it.
2. Check:
• Intake air temperature sensor resistance
Out of specification  Replace. Throttle position sensor input
voltage
4–6 V
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
Test harness S– pressure sensor
(3P)
90890-03207
Test harness S– pressure sensor
(3P)
YU-03207
• Positive tester probe 
Blue “1”
• Negative tester probe 
Black/Blue “2”
21
Intake air pressure sensor output
voltage
3.61–3.67 V at 101.3 kPa (3.61–
3.67 V at 1.01kgf/cm
2, 3.61–3.67
V at 14.7 psi)
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
• Positive tester probe 
Pink “1”
• Negative tester probe 
Black/Blue “2”
12

TROUBLESHOOTING
10-1
EAS2GBB405
TROUBLESHOOTING
EAS2GBB406GENERAL INFORMATION
TIP
The following guide for troubleshooting does
not cover all the possible causes of trouble. It
should be helpful, however, as a guide to basic
troubleshooting. Refer to the relative procedure
in this manual for checks, adjustments, and re-
placement of parts.
EAS2GBB407STARTING FAILURES
Engine
1. Cylinder and cylinder head
• Loose spark plug
• Loose cylinder head or cylinder
• Damaged cylinder head gasket
• Damaged cylinder gasket
• Worn or damaged cylinder
• Incorrect valve clearance
• Improperly sealed valve
• Incorrect valve-to-valve-seat contact
• Incorrect valve timing
• Faulty valve spring
• Seized valve
2. Piston and piston ring(s)
• Improperly installed piston ring
• Damaged, worn or fatigued piston ring
• Seized piston ring
• Seized or damaged piston
3. Air filter
• Improperly installed air filter
• Clogged air filter element
4. Crankcase and crankshaft
• Improperly assembled crankcase
• Seized crankshaft
Fuel system
1. Fuel tank
• Empty fuel tank
• Clogged fuel tank breather hose
• Deteriorated or contaminated fuel
• Clogged or damaged fuel hose
2. Fuel pump
• Faulty fuel pump
3. Throttle body
• Deteriorated or contaminated fuel
• Sucked-in airElectrical system
1. Battery
• Discharged battery
• Faulty battery
2. Fuse
• Blown, damaged or incorrect fuse
• Improperly installed fuse
3. Spark plug
• Incorrect spark plug gap
• Incorrect spark plug heat range
• Fouled spark plug
• Worn or damaged electrode
• Worn or damaged insulator
4. Ignition coil
• Cracked or broken ignition coil body
• Broken or shorted primary or secondary
coils
5. Ignition system
• Faulty ECU
• Faulty crankshaft position sensor
• Broken generator rotor woodruff key
6. Switches and wiring
• Faulty ECU
• Faulty engine stop switch
• Broken or shorted wiring
• Faulty neutral switch
• Improperly grounded circuit
• Loose connections
7. Starting system
• Faulty starter motor
• Faulty starter relay
• Faulty starting circuit cut-off relay
• Faulty starter clutch
EAS2GBB408INCORRECT ENGINE IDLING SPEED
Engine
1. Cylinder and cylinder head
• Incorrect valve clearance
• Damaged valve train components
2. Air filter
• Clogged air filter element
Fuel system
1. Throttle body
• Damaged or loose throttle body joint
• Improperly synchronized throttle bodies
• Improper throttle cable free play
• Flooded throttle body

TROUBLESHOOTING
10-2
Electrical system
1. Battery
• Discharged battery
• Faulty battery
2. Spark plug
• Incorrect spark plug gap
• Incorrect spark plug heat range
• Fouled spark plug
• Worn or damaged electrode
• Worn or damaged insulator
• Faulty spark plug cap
3. Ignition coil
• Broken or shorted primary or secondary coil
• Cracked or broken ignition coil
4. Ignition system
• Faulty ECU
• Faulty crankshaft position sensor
• Broken generator rotor woodruff key
EAS2GBB409POOR MEDIUM-AND-HIGH-SPEED PER-
FORMANCE
Refer to “STARTING FAILURES” on page 10-
1.
Engine
1. Air filter
• Clogged air filter element
Fuel system
1. Fuel pump
• Faulty fuel pump
2. Throttle body
• Defective throttle body
3. ECU
• Faulty ECU
EAS2GBB410SHIFTING IS DIFFICULT
Refer to “CLUTCH” on page 6-42.
EAS2GBB411SHIFT PEDAL DOES NOT MOVE
Engine
1. Shift shaft
• Bent shift shaft
2. Shift drum and shift forks
• Foreign object in a shift drum groove
• Seized shift fork
• Bent shift fork guide bar
3. Transmission
• Seized transmission gear
• Foreign object between transmission gears
• Improperly assembled transmission
EAS2GBB412
JUMPS OUT OF GEAR
Engine
1. Shift shaft
• Incorrect shift pedal position
• Improperly returned stopper lever
2. Shift forks
• Worn shift fork
3. Shift drum
• Incorrect axial play
• Worn shift drum groove
4. Transmission
• Worn gear dog
EAS2GBB413CLUTCH SLIPS
Engine
1. Clutch
• Improperly assembled clutch
• Loose or fatigued clutch spring
• Worn friction plate
• Worn clutch plate
2. Engine oil
• Incorrect oil level
• Incorrect oil viscosity (low)
• Deteriorated oil
EAS2GBB414CLUTCH DRAGS
Engine
1. Clutch
• Unevenly tensioned clutch springs
• Warped pressure plate
• Bent clutch plate
• Swollen friction plate
• Bent clutch push rod
• Damaged clutch boss
• Burnt primary driven gear bushing
2. Engine oil
• Incorrect oil level
• Incorrect oil viscosity (high)
• Deteriorated oil
EAS2GBB415OVERHEATING
Engine
1. Cylinder head and piston
• Heavy carbon buildup
• Clogged coolant passages
2. Engine oil
• Incorrect oil level
• Incorrect oil viscosity
• Inferior oil quality

TROUBLESHOOTING
10-3
Cooling system
1. Coolant
• Low coolant level
2. Radiator
• Damaged or leaking radiator
• Faulty radiator cap
• Bent or damaged radiator fin
3. Water pump
• Damaged or faulty water pump
• Damaged hose
• Improperly connected hose
• Damaged pipe
• Improperly connected pipe
Fuel system
1. Throttle body
• Damaged or loose throttle body joint
2. Air filter
• Clogged air filter element
Chassis
1. Brake(s)
• Dragging brake
Electrical system
1. Spark plug
• Incorrect spark plug gap
• Incorrect spark plug heat range
2. Ignition system
• Faulty ECU
• Faulty coolant temperature sensor
EAS2GBB416OVERCOOLING
Cooling system
1. Coolant temperature sensor
• Faulty coolant temperature sensor
EAS2GBB417POOR BRAKING PERFORMANCE
Chassis
1. Brake(s)
• Worn brake pad
• Worn brake disc
• Air in hydraulic brake system
• Leaking brake fluid
• Defective master cylinder kit
• Faulty brake caliper kit
• Faulty brake caliper seal
• Loose union bolt
• Damaged brake hose
• Oil or grease on the brake disc
• Oil or grease on the brake pad
• Incorrect brake fluid level
EAS2GBB418FRONT FORK OIL LEAKING
Chassis
1. Front fork
• Bent, damaged, or rusty inner tube
• Cracked or damaged outer tube
• Improperly installed oil seal
• Damaged oil seal lip
• Incorrect oil level (high)
• Loose damper rod assembly bolt
• Damaged damper rod assembly bolt copper
washer
• Cracked or damaged cap bolt O-ring
EAS2GBB419FAULTY FRONT FORK LEGS
Chassis
1. Front fork
• Bent or damaged inner tube
• Bent or damaged outer tube
• Broken fork spring
• Bent or damaged damper rod
• Incorrect oil viscosity
• Incorrect oil level
EAS2GBB420UNSTABLE HANDLING
Chassis
1. Handlebar
• Bent or improperly installed handlebar
2. Steering head components
• Improperly installed upper bracket
• Improperly installed lower bracket
(improperly tightened ring nut)
• Bent steering stem
• Damaged ball bearing or bearing race
3. Front fork leg (s)
• Uneven oil levels (both front fork legs)
• Unevenly tensioned fork spring (both front
fork legs)
• Broken fork spring
• Bent or damaged inner tube
• Bent or damaged outer tube
4. Swingarm
• Worn bearing or bushing
• Bent or damaged swingarm
5. Rear shock absorber assembly (-ies)
• Faulty rear shock absorber spring
• Leaking oil or gas
6. Tire (s)
• Uneven tire pressures (front and rear)
• Incorrect tire pressure
• Uneven tire wear