Poor Medium-And-High-Speed Performance; Faulty Gear Shifting; Shift Pedal Does Not Move; Jumps Out Of Gear - Yamaha WR250R Service Manual

Faulty spark plug cap
G
3. Ignition coil (s)
Faulty ignition coil
G
Cracked or broken ignition coil
G
4. Ignition system
ECU failure.
G
Faulty crankshaft position sensor
G
EAS28520
POOR MEDIUM-AND-HIGH-SPEED
PERFORMANCE
Refer to "STARTING FAILURES" on page 9-1.
Engine
1. Air filter
Clogged air filter element
G
Fuel system
1. Fuel pump
Faulty fuel pump
G
2. Throttle body
Defective throttle body
G
3. ECU
ECU failure.
G
EAS28530

FAULTY GEAR SHIFTING

Shifting is difficult
Refer to "Clutch drags".
EAS28540

SHIFT PEDAL DOES NOT MOVE

Shift shaft
Bent shift shaft
G
Shift drum and shift forks
Foreign object in a shift drum groove
G
Seized shift fork
G
Bent shift fork guide bar
G
Transmission
Seized transmission gear
G
Foreign object between transmission gears
G
Improperly assembled transmission
G
EAS28550

JUMPS OUT OF GEAR

Shift shaft
Incorrect shift pedal position
G
Improperly returned stopper lever
G
Shift forks
Worn shift fork
G
Shift drum
Incorrect axial play
G
Worn shift drum groove
G
Transmission
Worn gear dog
G
TROUBLESHOOTING
EAS28560

FAULTY CLUTCH

Clutch slips
1. Clutch
Improperly assembled clutch
G
Loose or fatigued clutch spring
G
Worn friction plate
G
Worn clutch plate
G
2. Engine oil
Incorrect oil level
G
Incorrect oil viscosity (low)
G
Deteriorated oil
G
Clutch drags
1. Clutch
Unevenly tensioned clutch springs
G
Warped pressure plate
G
Bent clutch plate
G
Swollen friction plate
G
Bent clutch push rod
G
Broken clutch boss
G
Burnt primary driven gear bushing
G
2. Engine oil
Incorrect oil level
G
Incorrect oil viscosity (high)
G
Deteriorated oil
G
EAS28590

OVERHEATING

Engine
1. Cylinder head (s) and piston (s)
Heavy carbon buildup
G
2. Engine oil
Incorrect oil level
G
Incorrect oil viscosity
G
Inferior oil quality
G
Cooling system
1. Coolant
Low coolant level
G
2. Radiator
Damaged or leaking radiator
G
Faulty radiator cap
G
Bent or damaged radiator fin
G
3. Water pump
Damaged or faulty water pump
G
Faulty thermostat
G
Damaged fan motor or disconnected coupler
G
Damaged hose
G
Improperly connected hose
G
Damaged pipe
G
Improperly connected pipe
G
Fuel system
1. Throttle body
Air intake in throttle body joint
G
2. Air filter
9-2