Engine; Adjusting The Pilot Air Screw; Checking The Engine Idling Speed; Checking The Throttle Grip - Yamaha YZ125 2022 Owner's Service Manual

EAM20135

ENGINE

EAM30607

ADJUSTING THE PILOT AIR SCREW

1. Adjust:
• Pilot air screw "1"
TIP
To optimize the fuel flow at a smaller throttle
opening, each vehicle's pilot air screw has been
individually set at the factory. Before adjusting
the pilot air screw, turn it in fully and count the
number of turns. Record this number as the fac-
tory-set number of turns out.
a. Turn in the pilot air screw until it is lightly
seated.
b. Turn out the pilot air screw to the factory-
set number of turns.
Air screw turns out
2-5/8
EAM30412

CHECKING THE ENGINE IDLING SPEED

1. Start the engine and thoroughly warm it up.
2. Adjust:
• Engine idling speed
a. Turn the throttle stop screw "1" until the
engine runs at the lowest possible speed.
b. Tighten the locknut.
EAM30475

CHECKING THE THROTTLE GRIP

TIP
Prior to adjusting throttle grip free play, the en-
1 1 1
1 1 1
3-5
gine idling speed should be adjusted.
1. Check:
• Throttle grip free play "a"
Out of specification  Regulate.
Throttle grip free play
3.0–5.0 mm (0.12–0.20 in)
a
G088895
2. Adjust:
• Throttle grip free play
a. Slide the adjuster cover.
b. Loosen the locknut "1".
c. Turn the adjuster "2" until the specified
free play is obtained.
d. Tighten the locknut.
EWA18470
WARNING
After adjusting the throttle grip free play,
start the engine and turn the handlebar to the
right and to the left to ensure that this does
not cause the engine idling speed to change.
EAM30254

CHECKING THE SPARK PLUG

1. Disconnect:
• Spark plug cap
2. Remove:
• Spark plug
ECA13330
NOTICE
Before removing the spark plug, blow away
any dirt accumulated in the spark plug well
with compressed air to prevent it from falling
ENGINE