Yamaha WR450F 2021 Owner's Service Manual page 374

Symptom
—
Excessive noise from engine
Symptom
Noise heard from around cylinder
head
Noise heard from around timing
chain
Possible cause
Worn camshaft lobe
Water or foreign material in fuel,
degraded fuel
Contaminated throttle body or
clogged internal passage
Incorrectly adjusted throttle cable
Incorrectly adjusted idling speed
(idle screw)
Incorrect throttle position sensor
angle
Incorrect acceleration position
sensor angle
Faulty ECU
Clogged vacuum hose
Cracks and damage in vacuum
hose
Damaged throttle body joint
Loose throttle body joint
Clogged air filter element
Incorrect oil level (high)
Possible cause
Incorrect valve clearance (too
wide)
Fatigued or broken valve spring
Worn or damaged camshaft lobe
Worn or damaged valve lifter
Worn or damaged camshaft jour-
nal
Worn or damaged cylinder head
(camshaft journal)
Worn or damaged timing chain
Worn or damaged camshaft
sprocket
Worn or damaged timing chain
guide
Cracked, damaged, or faulty tim-
ing chain tensioner
9-3
TROUBLESHOOTING
Actions
Replace the camshaft.
Change fuel.
Clean the throttle body.
Adjust the throttle grip free play.
Adjust the idle screw.
Adjust the throttle position sensor
angle.
Adjust the acceleration position
sensor angle.
Replace the ECU.
Clean the vacuum hose.
Replace the vacuum hose.
Replace the throttle body joint.
Tighten the throttle body joint bolts
to the specified torque.
Clean or replace the air filter ele-
ment.
Adjust the oil level to the specified
level.
Actions
Adjust the valve clearance.
Replace the valve spring.
Replace the camshaft.
Replace the valve lifter and cylin-
der head as a set.
Replace the camshaft.
Replace the cylinder head.
Replace the timing chain and cam-
shaft sprocket as a set.
Replace the timing chain and cam-
shaft sprocket as a set.
Replace the timing chain guide.
Replace the timing chain ten-
sioner.