Yamaha YZ250 2021 User Manual

ENGINE
3-5
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.
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.
EAM30475
CHECKING THE THROTTLE GRIP
TIP
Prior to adjusting throttle grip free play, the en-
gine idling speed should be adjusted.
1. Check:
• Throttle grip free play “a”
Out of specification  Regulate.
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.
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. Disconnect:
• Spark plug cap
2. Remove:
• Spark plug
NOTICE
ECA13330
Before removing the spark plug, blow away
any dirt accumulated in the spark plug well
with compressed air to prevent it from falling
Air screw turns out
1-1/4
Throttle grip free play
3.0–5.0 mm (0.12–0.20 in)
a
G088895

Yamaha YZ250 2021 Specifications

General

Engine Type	249cc liquid-cooled 2-stroke; reed-valve inducted
Bore x Stroke	66.4mm x 72.0mm
Compression Ratio	8.9~10.6:1
Ignition	CDI
Transmission	5-speed; multiplate wet clutch
Final Drive	Chain
Suspension Rear	KYB® single shock; fully adjustable, 12.4-in travel
Brakes Front	Hydraulic disc, 270mm
Tires Front	80/100-21
Tires Rear	110/90-19
Width	32.5 in
Height	50.8 in
Wheelbase	58.5 in
Ground Clearance	14.2 in
Fuel Capacity	2.1 gal
Wet Weight	227 lb
Fuel Delivery	Keihin PWK38S carburetor
Suspension Front	KYB® Speed-Sensitive System inverted fork; fully adjustable, 11.8-in travel
Brakes Rear	Hydraulic disc, 245mm