Starting A Warm Engine; Break-In Procedures; Engine Starting Precaution - Yamaha YZ450FN 2022 Owner's Service Manual

EAM30197

STARTING A WARM ENGINE

Follow the same procedure as for starting a cold
engine with the exception that the starter is not
required when the engine is warm.
TIP
If the engine fail to start, fully open the throttle
grip and push the start switch few seconds to
clear the engine of the rich air-fuel mixture re-
tained in it.
EAM30198

BREAK-IN PROCEDURES

A break-in is important so that rotating portion,
sliding surfaces, and mounted areas may fit one
another, and that the rider may become accus-
tomed to the machine.
ECA25811
NOTICE
Before running, do maintenance on the air
filter element.
1. After warming up the engine, drive it for about
20 minutes at a throttle opening of 1/2 or less.
TIP
This model is equipped with an engine auto-stop
system. The engine stops automatically if left
idling for 7 minutes. If the engine stops, push the
start switch to restart the engine.
2. Make a pit stop, and check mounted areas for
looseness, oil leaks, or other problems.
3. Then, drive it for about 40 minutes at a throt-
tle opening of 3/4 or less.
4. Make a pit stop again, and thoroughly check
mounted areas for looseness, oil leaks, or
other problems. Thorough checks and ad-
justments are required in particular for stretch
of cables, free play of the brake, stretch of the
drive chain, looseness of the spoke, and so
on.
ECA25821
NOTICE
After a break-in or after each race, always
1
1-25
STARTING AND BREAK-IN
check the points shown in "TORQUE-
CHECK POINTS" for tightening torques and
retighten them.
Also when the following parts are replaced, a
break-in is required.
• Cylinder and Crankshaft: A break-in is re-
quired for about an hour.
• Piston, Piston ring, Valve, Camshaft, and
Gear: A break-in is required for about 30
minutes at a throttle opening of 1/2 or less.
Observe the condition of the engine carefully
during a break-in.
For checkpoints for a break-in, see "MAIN-
TENANCE AFTER BREAK-IN". If any prob-
lem is found, immediately stop the engine
and make a checkup.
EAM30468

ENGINE STARTING PRECAUTION

• Make sure the transmission is in neutral or be
sure to pull the clutch lever before pressing the
start switch.
EWA20540
WARNING
If the clutch lever is not pulled and the start
switch is pressed with the transmission in
gear, the starter motor will cause the rear
wheel to spin, which may cause injury.
• When starting the engine, if only the starter
motor is turning but the engine does not crank,
this is a malfunction most likely due to a worn-
out starter clutch. Replace the starter clutch.