Yamaha YZ250 2022 Owner's Service Manual page 246

Symptom
—
Excessive noise from engine
Symptom
Noise heard from around piston
Noise heard from around crank-
shaft
Possible cause
Failed air induction system
Clogged vacuum hose
Cracks and damage in vacuum
hose
Damaged carburetor joint
Loose carburetor joint
Clogged air filter element
Possible cause
Worn or damaged piston ring
Worn or damaged piston
Worn piston (piston pin hole)
Worn or damaged piston pin
Worn or damaged cylinder bore
Carbon buildup in piston head and
combustion chamber
Worn or damaged crankshaft jour-
nal or crank pin
Worn or damaged big end bearing Replace the big end bearing.
Worn or damaged crankshaft jour-
nal bearing
Worn or damaged balancer shaft
journal bearing
9-5
TROUBLESHOOTING
Actions
Check the air induction system.
Repair or replace faulty parts.
Clean the vacuum hose.
Replace the vacuum hose.
Replace the carburetor joint.
Tighten the carburetor joint bolts
to the specified torque.
Clean or replace the air filter ele-
ment.
Actions
Replace the piston and piston
rings as a set.
Replace the piston and piston
rings as a set.
Replace the piston and piston pin
as a set.
Replace the piston pin.
Replace the cylinder, piston, and
piston rings as a set.
Clean the piston head and com-
bustion chamber.
Replace the crankshaft.
Replace the crankshaft journal
bearing.
Replace the balancer shaft journal
bearing.