YAMAHA YZ250F TROUBLESHOOTING and SOLVING CHARTS

February 8, 2023January 3, 2023 by Fatih

GENERAL INFORMATION

: Troubleshooting information provided here does not cover all the trouble symptoms, possible causes, and remedial actions. Some items may not apply depending on the model. Use this information as a guide and quick reference matrix when performing basic troubleshooting. Refer to the each chapter for detailed information on checking, adjustment, and replacement.

TROUBLESHOOTING OF ENGINE (fault code not detected)

: If a fault code is detected, refer to the FUEL INJECTION SYSTEM.

Engine does not crank.

Symptom	Possible cause	Actions
Starter motor does not operate	Refer to TROUBLESHOOTING under ELECTRIC STARTING SYSTEM.
Starter motor operates, but the engine does not crank.	Starter clutch malfunction	Replace the starter clutch.
	Improper oil grade (starter clutch slipping)	Change to recommended engine oil.
	Stuck piston or seized crankshaft	Disassemble and check the engine. Replace defective parts.

Engine will not start or is difficult to start, but it cranks.

Symptom	Possible cause	Actions
Spark plug does not produce a spark	Refer to TROUBLESHOOTING under IGNITION SYSTEM.
Fuel not supplied	—	Measure the fuel pressure.
	Empty fuel tank	Fill the fuel tank with fuel.
	Clogged fuel tank cap breather hole	Clean the fuel tank cap.
	Clogged or damaged fuel hose	Clean, repair, or replace the fuel hose.
	Fuel leakage	Check the fuel passage. Repair or replace as necessary.
	Clogged fuel pump	Clean or replace the fuel pump.
	Cracks or damage in fuel pump	Replace the fuel pump.
	Fuel pump malfunction	Refer to TROUBLESHOOTING under FUEL PUMP SYSTEM.
	Failed or clogged fuel injector	Replace the fuel injector.
	ECU failure	Replace the ECU.
—	Water or foreign material in fuel, degraded fuel	Change fuel.
	Loose spark plug	Tighten the spark plug to the specified torque.
	Loose cylinder head or cylinder	Tighten bolts or nuts on cylinder head and cylinder to the specified torque.
	Damaged cylinder head gasket	Replace the cylinder head gasket.
	Incorrect valve timing	Adjust the valve timing.
	Incorrect valve clearance	Adjust the valve clearance.
	Worn valve guide	Replace the valve guide.
	Bent, damaged, or stuck valve	Replace the valve.
	Poor contact between valve and valve seat	Reface the valve-to-valve-seat contact.
	Fatigued or broken valve spring	Replace the valve spring.
	Worn, damaged, or stuck piston ring	Replace the piston and piston rings as a set.
	Seized or damaged piston	Replace the piston and piston rings as a set.
	Worn or damaged cylinder bore	Replace the cylinder, piston, and piston rings as a set.

Incorrect idling speed or mid-to-high speed

Symptom	Possible cause	Actions
Spark plug does not produce a spark	Incorrect spark plug gap	Adjust the spark plug gap.
	Worn or damaged spark plug	Replace the spark plug.
	Defective spark plug cap	Replace the spark plug cap.
	Defective ignition coil	Replace the ignition coil.
	ECU failure	Replace the ECU.
Low fuel pressure	—	Measure the fuel pressure.
	Fuel leakage	Check the fuel passage. Repair or replace as necessary.
	Clogged fuel pump	Clean or replace the fuel pump.
	Cracks or damage in fuel pump	Replace the fuel pump.
	Fuel pump malfunction	Refer to TROUBLESHOOTING under FUEL PUMP SYSTEM.
Fuel not supplied	Failed or clogged fuel injector	Replace the fuel injector.
Fuel not supplied	ECU failure	Replace the ECU.
—	Worn camshaft lobe	Replace the camshaft.
	Water or foreign material in fuel, degraded fuel	Change fuel.
	Contaminated throttle body or clogged internal passage	Clean the throttle body.
	Incorrectly adjusted throttle cable	Adjust the throttle grip free play.
	Incorrectly adjusted idling speed (idle screw)	Adjust the idle screw.
	Incorrect throttle position sensor angle	Adjust the throttle position sensor angle.
	Incorrect acceleration position sensor angle	Adjust the acceleration position sensor angle.
	Faulty ECU	Replace the ECU.
	Clogged vacuum hose	Clean the vacuum hose.
	Cracks and damage in vacuum hose	Replace the vacuum hose.
	Damaged throttle body joint	Replace the throttle body joint.
	Loose throttle body joint	Tighten the throttle body joint bolts to the specified torque.
	Clogged air filter element	Clean or replace the air filter element.
	Incorrect oil level (high)	Adjust the oil level to the specified level.

Excessive noise from engine

Symptom	Possible cause	Actions
Noise heard from around cylinder head	Incorrect valve clearance (too wide)	Adjust the valve clearance.
	Fatigued or broken valve spring	Replace the valve spring.
	Worn or damaged camshaft lobe	Replace the camshaft.
	Worn or damaged valve lifter	Replace the valve lifter and cylinder head as a set.
	Worn or damaged camshaft journal	Replace the camshaft.
	Worn or damaged cylinder head (camshaft journal)	Replace the cylinder head.
Noise heard from around timing chain	Worn or damaged timing chain	Replace the timing chain and camshaft sprocket as a set.
	Worn or damaged camshaft sprocket	Replace the timing chain and camshaft sprocket as a set.
	Worn or damaged timing chain guide	Replace the timing chain guide.
	Cracked, damaged, or faulty timing chain tensioner	Replace the timing chain tensioner.
Noise heard from around piston	Worn or damaged piston ring	Replace the piston and piston rings as a set.
	Worn or damaged piston	Replace the piston and piston rings as a set.
	Worn piston (piston pin hole)	Replace the piston and piston pin as a set.
	Worn or damaged piston pin	Replace the piston pin.
	Worn or damaged cylinder bore	Replace the cylinder, piston, and piston rings as a set.
	Carbon buildup in piston head and combustion chamber	Clean the piston head and combustion chamber.
Noise heard from around crankshaft	Worn or damaged crankshaft journal or crank pin	Replace the crankshaft.
	Cracked, worn, or damaged balancer shaft	Replace the balancer drive gear and balancer shaft as a set.
	Worn or damaged balancer drive gear	Replace the balancer drive gear and balancer shaft as a set.
	Worn or damaged big end bearing	Replace the big end bearing.
	Worn or damaged crankshaft journal bearing	Replace the crankshaft journal bearing.
	Worn or damaged balancer shaft journal bearing	Replace the balancer shaft journal bearing.

TROUBLESHOOTING OF CLUTCH

Manual clutch

Symptom	Possible cause	Actions
Clutch slippage	Improperly assembled clutch	Reassemble the clutch.
	Improperly adjusted clutch cable	Adjust the clutch lever free play.
	Loose clutch spring	Tighten the clutch spring bolts to the specified torque.
	Fatigued clutch spring	Replace the clutch springs as a set.
	Warped pressure plate	Replace the pressure plate.
	Worn friction plate	Replace the friction plates as a set.
	Warped or worn clutch plate	Replace the clutch plates as a set.
	Incorrect oil level	Adjust the engine oil level to the specified level.
	Incorrect oil viscosity (low)	Change to recommended engine oil.
	Deteriorated oil	Change to recommended engine oil.
Clutch drags	Faulty clutch spring	Replace the clutch springs as a set.
	Warped pressure plate	Replace the pressure plate.
	Swollen friction plate	Replace the friction plates as a set.
	Warped clutch plate	Replace the clutch plates as a set.
	Bent pull rod (outer pull type)	Replace the pull rod.
	Worn pull rod tooth (outer pull type)	Replace the pull rod and pull lever shaft as a set.
	Bent push rod (inner push type)	Replace the push rod.
	Damaged or worn clutch boss	Replace the clutch boss.
	Seized clutch housing bushing	Replace the clutch housing.
	Improperly installed pull lever	Align the match mark on the pull lever before installation.
	Incorrect oil level	Adjust the engine oil level to the specified level.
	Incorrect oil viscosity (high)	Change to recommended engine oil.
	Deteriorated oil	Change to recommended engine oil.
Clutch noise	Damaged or worn primary driven gear	Replace the primary drive gear or crankshaft, and the clutch housing as a set.
	Loose clutch boss nut	Tighten the clutch boss nut to the specified torque.
	Fatigued clutch damper	Replace the clutch housing.
	Worn clutch housing bearing	Replace the clutch housing bearing.
	Worn pressure plate bearing	Replace the pressure plate bearing.

TROUBLESHOOTING OF TRANSMISSION

Symptom	Possible cause	Actions
Difficult or impossible to shift transmission gear	Clutch drags	Refer to “Clutch drags”.
	Improperly adjusted shift rod	Adjust the shift rod installation length.
	Bent shift shaft	Replace the shift shaft.
	Foreign object in a shift drum groove	Remove foreign object from shift drum groove.
	Damaged shift drum	Replace the shift drum.
	Seized shift fork	Replace the shift fork and shift fork guide bar as a set.
	Bent shift fork guide bar	Replace the shift fork guide bar.
	Foreign object between transmission gears	Remove foreign object from transmission gears.
	Seized transmission gear	Replace the seized gear and the axle as a set.
	Improperly assembled transmission	Reassemble the transmission axle assembly.
Jumps out of gear	Incorrect shift pedal position	Adjust the shift pedal position.
	Improperly returned stopper lever	Replace the stopper lever spring.
	Bent or worn shift fork	Replace the shift fork.
	Shift drum incorrect axial play	Replace the shift drum.
	Worn shift drum groove	Replace the shift drum.
	Worn transmission gear dog	Replace the transmission gear.
Transmission noise	Damaged or worn transmission gear	Replace the transmission gear.
	Worn main axle spline	Replace the main axle.
	Worn drive axle spline	Replace the drive axle.
	Worn bearing	Replace the bearing.

TROUBLESHOOTING OF COOLING SYSTEM

Symptom	Possible cause	Actions
Overheating	Carbon buildup in piston head and combustion chamber	Clean the piston head and combustion chamber.
	Clogged engine cooling water passages	Check and clean the engine cooling water passages.
	Incorrect oil level	Adjust the oil level to the specified level.
	Incorrect oil viscosity	Change to recommended engine oil.
	Inferior oil quality	Change to recommended engine oil.
	Low coolant level	Add recommended coolant to the specified level.
	Damaged or leaking radiator	Replace the radiator.
	Faulty radiator cap	Replace the radiator cap.
	Clogged radiator fin	Clean the radiator fin.
	Bent or damaged radiator fin	Repair the radiator fin or replace the radiator.
	Damaged or faulty water pump	Replace the water pump.
	Damaged hoses or pipes	Replace the hose or pipe.
	Improperly connected hoses or pipes	Connect the hoses and pipes properly.
	Damaged throttle body joint	Replace the throttle body joint.
	Loose throttle body joint	Tighten the throttle body joint bolts to the specified torque.
	Clogged air filter element	Clean or replace the air filter element.
	Brake drags	Check the brake system and repair or replace faulty parts as necessary.
	Incorrect spark plug gap	Adjust to the specified spark plug gap.
	Incorrect spark plug heat range	Replace the spark plug with the one of the specified type.
	Faulty ECU	Replace the ECU.
Noise from water pump	Contact between the water pump housing cover and impeller	Disassemble the water pump and replace faulty parts.
Noise from water pump	Worn water pump housing bearing	Replace the water pump housing bearing.

TROUBLESHOOTING OF BRAKE

Symptom	Possible cause	Actions
Poor performance of disc brake	Worn brake pad	Replace the brake pads as a set.
	Worn or deflected brake disc	Replace the brake disc.
	Air in hydraulic brake system	Bleed the hydraulic brake system.
	Brake fluid leakage	Check the hydraulic brake system and repair or replace faulty parts as necessary.
	Incorrect brake fluid level (low)	Add brake fluid to the specified level.
	Stuck brake caliper piston	Replace the caliper piston seal.
	Stuck brake caliper and slide pin	Lubricate the caliper slide pin.
	Loose union bolt	Tighten the union bolt to the specified torque.
	Damaged brake hose and brake pipe	Replace the brake hose and brake pipe.
	Oil or grease on the brake disc or brake pad	Clean the brake disc or brake pad.
	Insufficient lubrication of brake lever or brake pedal pivot	Lubricate the brake lever or brake pedal pivot.

TROUBLESHOOTING OF SUSPENSION

Symptom	Possible cause	Actions
Front fork is hard	Bent or damaged inner tube	Replace the inner tube.
	Bent or damaged outer tube	Replace the outer tube.
	Damaged or worn slide metal	Replace the slide metal.
	Bent or damaged damper rod	Replace the damper rod.
	Bent wheel axle	Replace the wheel axle.
	Incorrect oil viscosity (high)	Change to recommended fork oil.
	Incorrect oil level (high)	Adjust to the specified oil level.
	Improperly adjusted spring preload (hard)	Adjust the spring preload.
	Improperly adjusted rebound damping (hard)	Adjust the rebound damping.
	Improperly adjusted compression damping (hard)	Adjust the compression damping.
Front fork is soft	Fatigued or broken fork spring	Replace the fork spring.
	Incorrect oil viscosity (low)	Change to recommended fork oil.
	Incorrect oil level (low)	Adjust to the specified oil level.
	Improperly adjusted spring preload (soft)	Adjust the spring preload.
	Improperly adjusted rebound damping (soft)	Adjust the rebound damping.
	Improperly adjusted compression damping (soft)	Adjust the compression damping.
Leaking oil from front fork	Bent, damaged, or corroded inner tube	Replace the inner tube.
	Cracked or damaged outer tube	Replace the outer tube.
	Improperly installed oil seal	Replace the oil seal.
	Damaged oil seal lip	Replace the oil seal.
	Incorrect oil level (high)	Adjust to the specified oil level.
	Loose damper rod assembly bolt	Tighten the damper rod assembly bolt to the specified torque.
	Damaged damper rod assembly bolt copper washer	Replace the damper rod assembly bolt copper washer.
	Cracked or damaged cap bolt O-ring	Replace the cap bolt O-ring.
Rear suspension is hard	Bent or damaged rear shock absorber rod	Replace the rear shock absorber.
	Bent swingarm pivot shaft	Replace the swingarm pivot shaft.
	Damaged or worn swingarm bearing or bushing	Replace the swingarm bearing or bushing.
	Damaged or worn relay arm bearing	Replace the relay arm bearing.
	Damaged or worn connecting arm bearing	Replace the connecting arm bearing.
	Improperly adjusted rear shock absorber spring preload (hard)	Adjust the spring preload.
	Improperly adjusted rear shock absorber rebound damping (hard)	Adjust the rebound damping.
	Improperly adjusted rear shock absorber compression damping (hard)	Adjust the compression damping.
Rear suspension is soft	Oil leaking from rear shock absorber	Replace the rear shock absorber.
	Gas leaking from rear shock absorber	Replace the rear shock absorber.
	Fatigued or damaged rear shock absorber spring	Replace the rear shock absorber.
	Improperly adjusted rear shock absorber spring preload (soft)	Adjust the spring preload.
	Improperly adjusted rear shock absorber rebound damping (soft)	Adjust the rebound damping.
	Improperly adjusted rear shock absorber compression damping (soft)	Adjust the compression damping.
Oil leaking from rear shock absorber	Bent, damaged, or corroded rear shock absorber rod	Replace the rear shock absorber.
Oil leaking from rear shock absorber	Damaged oil seal lip	Replace the rear shock absorber.

TROUBLESHOOTING OF STEERING/HANDLING

Symptom	Possible cause	Actions
Handlebar wobble	Loose lower ring nut	Tighten the lower ring nut to the specified torque.
	Worn bearing or bearing race	Replace the bearing and bearing race as a set.
	Warped front fork	Repair or replace the front fork.
	Bent front wheel axle	Replace the front wheel axle.
	Incorrect tire pressure	Adjust to the specified tire pressure.
	Worn, deformed, or incorrect tire	Replace the tire.
Heavy steering	Lower ring nut is tightened too tight.	Tighten the lower ring nut to the specified torque.
	Bent lower bracket	Replace the lower bracket.
	Broken bearing or bearing race	Replace the bearing and bearing race as a set.
	Incorrect tire pressure	Adjust to the specified tire pressure.
Front wheel vibration	Loose spoke	Tighten the spoke and adjust the runout.
	Damaged or worn wheel bearing	Replace the wheel bearing.
	Worn, deformed, or incorrect tire	Replace the tire.
	Loose wheel axle or wheel axle nut	Tighten the wheel axle or wheel axle nut to the specified torque.
	Loose wheel axle pinch bolt	Tighten the wheel axle pinch bolt to the specified torque.
	Incorrect front fork oil level	Adjust to the specified front fork oil level.
Rear wheel vibration	Loose spoke	Tighten the spoke and adjust the runout.
	Damaged or worn wheel bearing	Replace the wheel bearing.
	Worn, deformed, or incorrect tire	Replace the tire.
	Loose wheel axle nut	Tighten the wheel axle nut to the specified torque.
	Loose swingarm pivot shaft	Tighten the swingarm pivot shaft to the specified torque.
	Bent or damaged swingarm	Replace the swingarm bearing.
	Damaged or worn swingarm bearing or bushing	Replace the swingarm bearing or bushing.

TROUBLESHOOTING OF CHARGING SYSTEM

Symptom	Possible cause	Actions
Battery is not charged	Refer to TROUBLESHOOTING under CHARGING SYSTEM.

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