2003 YAMAHA YZ250LC fuel

5. GASOLINE IS HIGHLY FLAMMABLE.
Always turn off the engine while refuel-
ing. Take care to not spill any gasoline
on the engine or exhaust system.
Never refuel in the vicinity of an open
flame, or while smoking.
6. GASOLINE CAN CAUSE INJURY.
If you should swallow some gasoline,
inhale excess gasoline vapors, or allow
any gasoline to get into your eyes, con-
tact a doctor immediately. If any gaso-
line spills onto your skin or clothing,
immediately wash skin areas with soap
and water, and change your clothes.
7. ONLY OPERATE THE MACHINE IN AN
AREA WITH ADEQUATE VENTILATION.
Never start the engine or let it run for
any length of time in an enclosed area.
Exhaust fumes are poisonous. These
fumes contain carbon monoxide, which
by itself is odorless and colorless.
Carbon monoxide is a dangerous gas
which can cause unconsciousness or
can be lethal.
8. PARK THE MACHINE CAREFULLY;
TURN OFF THE ENGINE.
Always turn off the engine if you are
going to leave the machine. Do not
park the machine on a slope or soft
ground as it may fall over.
9. PROPERLY SECURE THE MACHINE
BEFORE TRANSPORTING IT.
When transporting the machine in
another vehicle, always be sure it is
properly secured and in an upright
position and that the fuel cock is in the
“OFF” position. Otherwise, fuel may
leak out of the carburetor or fuel tank.
5UP-9-30-0 5/24/02 5:13 PM Page 6

EC050000
TO THE NEW OWNER
This manual will provide you with a good basic
understanding of features, operation, and basic
maintenance and inspection items of this
machine. Please read this manual carefully and
completely before operating your new machine.
If you have any questions regarding the opera-
tion or maintenance of your machine, please
consult your Yamaha dealer.
NOTE:
This manual should be considered a permanent
part of this machine and should remain with it
even if the machine is subsequently sold.
EC060000
NOTICE
Some data in this manual may become out-
dated due to improvements made to this
model in the future. If there is any question
you have regarding this manual or your
machine, please consult your Yamaha
dealer.
Weights of machines without fuel
The minimum weights for motocross
machines are:
for the class 125 cc ........................minimum
88 kg (194 lb)
for the class 250 cc ........................minimum
98 kg (216 lb)
for the class 500 cc ........................minimum
102 kg (225 lb)
In modifying your machine (e.g., for weight
reduction), take note of the above limits of
weight.
EC070001
F.I.M. MACHINE WEIGHTS:
5UP-9-30-0 5/24/02 5:13 PM Page 8

EC0A0000
CONTENTS
CHAPTER 1
GENERAL INFORMATION
DESCRIPTION............................................1-1
MACHINE IDENTIFICATION......................1-2
IMPORTANT INFORMATION.....................1-3
CHECKING OF CONNECTION..................1-6
SPECIAL TOOLS........................................1-7
CONTROL FUNCTIONS.............................1-9
FUEL AND ENGINE MIXING OIL.............1-12
STARTING AND BREAK-IN.....................1-13
TORQUE-CHECK POINTS.......................1-16
CLEANING AND STORAGE....................1-17
CHAPTER 2
SPECIFICATIONS
GENERAL SPECIFICATIONS....................2-1
MAINTENANCE SPECIFICATIONS...........2-3
GENERAL TORQUE SPECIFICATIONS..2-12
DEFINITION OF UNITS............................2-12
CABLE ROUTING DIAGRAM..................2-13
CHAPTER 3
REGULAR INSPECTION
AND ADJUSTMENTS
MAINTENANCE INTERVALS.....................3-1
PRE-OPERATION INSPECTION AND
MAINTENANCE..........................................3-4
ENGINE.......................................................3-5
CHASSIS...................................................3-17
ELECTRICAL............................................3-38
5UP-9-30-0 5/24/02 5:13 PM Page 18

CHAPTER 4
ENGINE
SEAT, FUEL TANK AND SIDE
COVERS.....................................................4-1
EXHAUST PIPE AND SILENCER..............4-3
RADIATOR..................................................4-4
CARBURETOR AND REED VALVE...........4-7
CYLINDER HEAD , CYLINDER AND
PISTON.....................................................4-18
CLUTCH AND PRIMARY DRIVEN
GEAR.......................................................4-33
KICK AXLE, SHIFT SHAFT AND
PRIMARY DRIVE GEAR...........................4-40
YPVS GOVERNOR...................................4-49
WATER PUMP..........................................4-52
CDI MAGNETO.........................................4-56
ENGINE REMOVAL..................................4-60
CRANKCASE AND CRANKSHAFT.........4-65
TRANSMISSION, SHIFT CAM AND
SHIFT FORK.............................................4-72
CHAPTER 5
CHASSIS
FRONT WHEEL AND REAR WHEEL........5-1
FRONT BRAKE AND REAR BRAKE.......5-10
FRONT FORK...........................................5-26
HANDLEBAR............................................5-39
STEERING................................................5-46
SWINGARM..............................................5-51
REAR SHOCK ABSORBER.....................5-59
5UP-9-30-0 5/24/02 5:13 PM Page 20

1-1
DESCRIPTION
GEN
INFO
EC100000
GENERAL INFORMATION
EC110000
DESCRIPTION
1Clutch lever
2“ENGINE STOP” button
3Front brake lever
4Throttle grip
5Radiator cap
6Fuel tank cap
7Kick starter
8Fuel tank
9Radiator
0Coolant drain bolt
qCheck bolt (Transmission oil level)
wRear brake pedal
eValve joint
rFuel cock
tStarter knob
yDrive chain
uAir cleaner
iShift pedal
oFront fork
NOTE:
9The machine you have purchased may differ
slightly from those shown in the following.
9Designs and specifications are subject to
change without notice.
5UP-9-30-1 5/24/02 5:15 PM Page 2

1-10
CONTROL FUNCTIONS
GEN
INFO
EC156000
FRONT BRAKE LEVER
The front brake lever 1is located on the right
handlebar. Pull it toward the handlebar to acti-
vate the front brake.
EC157000
REAR BRAKE PEDAL
The rear brake pedal 1is located on the right
side of the machine. Press down on the brake
pedal to activate the rear brake.
EC158001
FUEL COCK
The fuel cock supplies fuel from the tank to car-
buretor while filtering the fuel. The fuel cock has
the two positions:
OFF: With the lever in this position, fuel will not
flow. Always return the lever to this posi-
tion when the engine is not running.
ON: With the lever in this position, fuel flows to
the carburetor. Normal riding is done with
the lever in this position.
EC159000
STARTER KNOB (CHOKE)
When cold, the engine requires a richer air-fuel
mixture for starting. A separate starter circuit,
which is controlled by the starter knob 1, sup-
plies this mixture. Pull the starter knob out to
open the circuit for starting. When the engine
has warmed up, push it in to close the circuit.
5UP-9-30-1 5/24/02 5:15 PM Page 24

1-11
CONTROL FUNCTIONS
GEN
INFO
EC15F000
VALVE JOINT
This valve joint 1prevents fuel from flowing out
and is installed to the fuel tank breather hose.
cC
In this installation, make sure the arrow
faces the fuel tank and also downward.
EC15R001
DETACHABLE SIDESTAND
This sidestand 1is used to support only the
machine when standing or transporting it.
w
9Never apply additional force to the side-
stand.
9Remove this sidestand before starting
out.
EC15f000
SET PIN
This set pin 1is used to remove and install the
push rod of the engine.
cC
Be sure to use the set pin. If the set pin is
not used, the power valve constituent parts
will result in damage.
EC15e000
NIPPLE WRENCH
This nipple wrench 1is used to tighten the
spoke.
5UP-9-30-1 5/24/02 5:15 PM Page 26

1-12
FUEL AND ENGINE MIXING OIL
GEN
INFO
EC160051
FUEL AND ENGINE MIXING OIL
Mix oil with the gas at the ratio specified below.
Always use fresh, name-brand gasoline, and mix
the oil and gas the day of the race. Do not use
premix that is more than a few hours old.
NOTE:
If knocking or pinging occurs, use a different
brand of gasoline or higher octane grade.
cC
Never mix two types of oil in the same
batch; clotting of the oil could result. If you
wish to change oil types, be sure to drain
the fuel tank and the carburetor float bowl
of old premix prior to filling with the new
type.
Fuel tank capacity:
8.0 L (1.76 Imp gal, 2.11 US gal)
Mixing oil
Recommended oil:
Yamalube “2-R”
(Yamalube racing 2-cycle oil)
Mixing ratio: 30 : 1
If unavailable, use an equivalent
type of oil.
Recommended fuel:
Except for ZA:
Premium unleaded gasoline
only with a research octane
number of 95 or higher.
For ZA:
Premium gasoline
5UP-9-30-1 5/24/02 5:15 PM Page 28