2005 YAMAHA YZ250LC engine

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.
1P8-9-30-0 19/5/04 8:58 AM Page 6

EC080000
HOW TO USE
THIS MANUAL
EC081000
PARTICULARLY IMPORTANT IN
FORMATION
Q
The Safety Alert Symbol means ATTENTION!
BECOME ALERT! YOUR SAFETY IS
INVOLVED!
w
Failure to follow WARNING instructions could
result in severe injury or death to the machine
operator, a bystander, or a person inspecting or
repairing the machine.
cC
A CAUTION indicates special precautions that
must be taken to avoid damage to the machine.
NOTE:
A NOTE provides key information to make pro-
cedures easier or clearer.
EC082000
FINDING THE REQUIRED PAGE
1. This manual consists of seven chapters;
“General Information”, “Specifications”,
“Regular inspection and adjustments”,
“Engine”, “Chassis”, “Electrical” and “Tun-
ing”.
2. The table of contents is at the beginning of
the manual. Look over the general layout of
the book before finding then required chap-
ter and item.
Bend the book at its edge, as shown, to find
the required fore edge symbol mark and go
to a page for required item and description.
1P8-9-30-0 19/5/04 8:58 AM Page 10

EC085002
ILLUSTRATED SYMBOLS
(Refer to the illustration)
Illustrated symbols 1to 7are designed as
thumb tabs to indicate the chapter’s number and
content.
1
General information
2Specifications
3Regular inspection and adjustments
4Engine
5Chassis
6Electrical
7Tuning
Illustrated symbols 8to rare used to identify
the specifications appearing in the text.
8
With engine mounted
9Special tool
0Filling fluid
qLubricant
wTightening
eSpecified value, Service limit
rResistance (Ω), Voltage (V), Electric current (A)
Illustrated symbols tto oin the exploded dia-
grams indicate grade of lubricant and location of
lubrication point.
t
Apply transmission oil
yApply engine mixing oil
uApply molybdenum disulfide oil
iApply lightweight lithium-soap base grease
oApply molybdenum disulfide grease
Illustrated symbols pto ain the exploded dia-
grams indicate where to apply a locking agent
and where to install new parts.
p
Apply locking agent (LOCTITER)
aUse new one
GEN
INFO
12
3
5
74
6
8
90
qw
er
tyu
io
pa
SPEC
INSP
ADJENG
CHASELEC
TUN
1P8-9-30-0 19/5/04 8:58 AM Page 14

EC090010
INDEX
GENERAL
INFORMATION
SPECIFICATIONS
REGULAR
INSPECTION AND
ADJUSTMENTS
ENGINE
CHASSIS
ELECTRICAL
TUNING
1P8-9-30-0 19/5/04 8:58 AM Page 16

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..2-13
DEFINITION OF UNITS............................2-13
CABLE ROUTING DIAGRAM..................2-14
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
1P8-9-30-0 19/5/04 8:58 AM 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............................................5-41
STEERING................................................5-48
SWINGARM..............................................5-53
REAR SHOCK ABSORBER.....................5-61
1P8-9-30-0 19/5/04 8:58 AM Page 20

CHAPTER 6
ELECTRICAL
ELECTRICAL COMPONENTS AND
WIRING DIAGRAM.....................................6-1
IGNITION SYSTEM.....................................6-2
SOLENOID VALVE SYSTEM.....................6-7
TPS (THROTTLE POSITION SENSOR)
SYSTEM......................................................6-9
CHAPTER 7
TUNING
ENGINE.......................................................7-1
CHASSIS...................................................7-13
1P8-9-30-0 19/5/04 8:58 AM Page 22

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.
1P8-9-30-1 19/5/04 9:00 AM Page 2