Yamaha YZ 2019 Series, Owner'S Service Manual, Page: 33 / 398

STARTING AND BREAK-IN
1-21
NOTICE
ECA25920
If the starter motor will not turn when the
start switch is pushed, stop pushing it imme-
diately in order to avoid placing extra load on
the starter motor.
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.
4. When the engine starts running, warm this up
one or two minutes at a steady speed (of
3000 to 5000 r/min), and then return the start-
er knob/idle screw to its original position.
WARNING
EWA19030
Since exhaust gas contains harmful ingredi-
ents, do not start or warm it up at an illventi-
lated place or a closed narrow place.
5. To stop the engine, push the engine stop
switch “1”.
TIP
Continue pushing the engine stop switch till the
engine comes to a full stop.
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.
NOTICE
ECA25811
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.
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.
NOTICE
ECA25821
After a break-in or after each race, always
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.