Chassis; Changing The Transmission Oil; Adjusting The Pilot Air Screw; Adjusting The Engine Idling Speed - Yamaha YZ250 Owner's Service Manual

CHANGING THE TRANSMISSION
OIL
1. Start the engine and warm it up
for several minutes and wait for
five minute.
2. Place the machine on a level
place and hold it on upright posi-
tion by placing the suitable stand
under the engine.
3. Place a suitable container under
the engine.
4. Remove:
• Oil drain bolt "1"
• Oil filler cap "2"
Drain the transmission oil.
5. Install:
• Aluminum washer
• Oil drain bolt "1"
Oil drain bolt:
23 Nm (2.3 m•kg, 17
ft•lb)
6. Fill:
• Transmission oil
Recommended oil:
Yamalube 4 (10W-40)
or SAE 10W-40 type SE
motor oil
Oil capacity (periodic oil
change):
0.75 L (0.66 Imp qt, 0.79
US qt)
7. Check:
• Oil leakage
8. Check:
• Transmission oil level
9. Install:
• Oil filler cap "2"
ADJUSTING THE PILOT AIR
SCREW
1. Adjust:
• Pilot air screw "1"
Adjustment steps:
a. Turn in the pilot air screw until it is
lightly seated.
b. Turn out the pilot air screw by the
factory-set number of turns.
To optimize the fuel flow at a smaller
throttle opening, each machine'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 factory-set number of turns
out.
Pilot air screw:
1 turn out
* 2-1/4 turns out
(for reference only)
* Except for USA and CDN
ADJUSTING THE ENGINE IDLING
SPEED
1. Start the engine and thoroughly
warm it up.
2. Adjust:
• Engine idling speed
Adjustment steps:
a. Turn the throttle stop screw "1"
until the engine runs at the lowest
possible speed.
To increase idle speed→Turn the
throttle stop screw "1" in.
To decrease idle speed→Turn the
throttle stop screw "1" out.

CHECKING THE EXHAUST PIPE

1. Inspect:
• O-ring "1"
Damage → Replace.
Install the O-rings with their de-
pressed "a" facing outward.
3-8

CHASSIS

CHASSIS
BLEEDING THE HYDRAULIC
BRAKE SYSTEM
Bleed the brake system if:
• The system has been disassem-
bled.
• A brake hose has been loosened
or removed.
• The brake fluid is very low.
• The brake operation is faulty.
A dangerous loss of braking per-
formance may occur if the brake
system is not properly bled.
1. Remove:
• Brake master cylinder cap
• Diaphragm
• Reservoir float (front brake)
• Protector (rear brake)
2. Bleed:
• Brake fluid
Air bleeding steps:
a. Add proper brake fluid to the res-
ervoir.
b. Install the diaphragm. Be careful
not to spill any fluid or allow the
reservoir to overflow.
c. Connect the clear plastic tube "2"
tightly to the caliper bleed screw
"1".
A. Front
B. Rear
d. Place the other end of the tube
into a container.
e. Slowly apply the brake lever or
pedal several times.