Yamaha WR450F 2021, Owner'S Service Manual, Page: 103 / 402

ENGINE
3-13
2. Adjust:
• Throttle grip free play
a. Loosen the locknut “1”.
b. Turn the adjuster “2” until the specified
throttle grip free play is obtained.
c. Tighten the locknut.
WARNING
EWA18470
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. Remove:
• Seat
•
Air scoop (left/right)
Refer to “GENERAL CHASSIS” on page 4-1.
•
Fuel tank “1”
Refer to “FUEL TANK” on page 7-1.
NOTICE
ECA24400
Do not use too much force to pull the hose.
TIP
Remove the fuel tank, turn this 180

clockwise,
and put it in the frame “2” as shown.
2. Remove:
• Spark plug cap
•
Spark plug
Refer to “CAMSHAFT” on page 5-13.
NOTICE
ECA24410
In order not to allow the dirt accumulated
around the spark plug to drop from the spark
plug hole into the cylinder, clean it before re-
moving the spark plug.
3. Check:
•
Spark plug type
Wrong type

Replace.
4. Check:
• Electrode
Damage/wear

Replace the spark plug.
• Insulator
Abnormal color

Replace the spark plug.
Normal color is medium-to-light tan.
5. Clean:
• Spark plug
(with a spark plug cleaner or a wire brush)
6. Measure:
•
Spark plug gap “a”
Out of specification

Adjust the spark plug
gap.
7. Install:
•
Spark plug
TIP
Before installing the spark plug, clean the spark
plug and gasket surface.
8. Install:
•
Spark plug cap
•
Fuel tank
•
Air scoop (left/right)
•
Seat
1
2
1
1
2
Manufacturer/model
NGK/LMAR8G
Spark plug gap
0.7–0.8 mm (0.028–0.031 in)
Spark plug
13 N·m (1.3 kgf·m, 9.6 lb·ft)
T
R
.
.