fuel YAMAHA YZ125LC 2007 Owners Manual

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 an-
other vehicle, always be sure it is prop-
erly 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.
1C3-9-32-0 4/28/06 9:45 AM 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 ma-
chine. 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 deal-
er.
Weights of machines without fuel
The minimum weights for motocross ma-
chines 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:
1C3-9-32-0 4/28/06 9:45 AM 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............................................3-39
1C3-9-32-0 4/28/06 9:45 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.....................................................4-17
CLUTCH AND PRIMARY DRIVEN
GEAR.......................................................4-30
KICK AXLE, SHIFT SHAFT AND
PRIMARY DRIVE GEAR...........................4-37
YPVS GOVERNOR...................................4-45
WATER PUMP..........................................4-48
CDI MAGNETO.........................................4-52
ENGINE REMOVAL..................................4-56
CRANKCASE AND CRANKSHAFT.........4-61
TRANSMISSION, SHIFT CAM AND
SHIFT FORK.............................................4-69
CHAPTER 5
CHASSIS
FRONT WHEEL AND REAR WHEEL........5-1
FRONT BRAKE AND REAR BRAKE.......5-10
FRONT FORK...........................................5-26
HANDLEBAR............................................5-42
STEERING................................................5-50
SWINGARM..............................................5-55
REAR SHOCK ABSORBER.....................5-63
1C3-9-32-0 4/28/06 9:45 AM Page 20

1-1
GEN
INFO
DESCRIPTION
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
tAir cleaner
yDrive chain
uShift pedal
iStarter knob
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.
1C3-9-32-1A 4/12/06 4:38 PM Page 2

1-7
GEN
INFO
SPECIAL TOOLS
EC140002
SPECIAL TOOLS
The proper special tools are necessary for complete and accurate tune-up and assembly. Using the
correct special tool will help prevent damage caused by the use of improper tools or improvised tech-
niques. The shape and part number used for the special tool differ by country, so two types are provid-
ed. Refer to the list provided to avoid errors when placing an order.
NOTE:
9For U.S.A. and Canada, use part number starting with “YM-”, “YU-” or “ACC-”.
9For others, use part number starting with “90890-”.
Part number Tool name / How to use IIIustration
YU-1135-A, 90890-01135Crankcase separating toolYU-1135-A 90890-01135
These tool is used to split the crankcase as well
as remove the crankshaft from either case.
YM-1189, 90890-01189 Flywheel puller
YM-1189 90890-01189
This tool is used to remove the flywheel magneto.
YU-1235, 90890-01235 Rotor holding tool
YU-1235 90890-01235
This tool is used when loosening or tightening the
flywheel magneto securing nut.
YU-3097, 90890-01252 Dial gauge and stand
YU-3097 90890-01252
YU-1256 Spark plug hole dial standYU-1256
These tools are used to set the ignition timing.
Crankcase installing tool
YU-90050 90890-01274
YU-90050, 90890-01274 PotYU-90063 90890-01275
YU-90050, 90890-01275 BoltYM-0149990890-01278
YU-90063, 90890-01278 Adapter90890-01499
YM-01499, 90890-01499 Adapter
These tools are used to install the crankshaft.
YU-1304, 90890-01304 Piston pin puller
YU-1304 90890-01304
This tool is used to remove the piston pin.
YM-1312-A, 90890-01312Fuel level gaugeYM-1312-A 90890-01312
YM-01470, 90890-01470 Fuel level gauge adaptorYM-01470 90890-01470
This gauge is used to measure the fuel level in the
float chamber.
1C3-9-32-1A 4/12/06 4:38 PM Page 14

1-10
GEN
INFO
CONTROL FUNCTIONS
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.
1C3-9-32-1A 4/12/06 4:38 PM Page 24

1-11
GEN
INFO
CONTROL FUNCTIONS
EC15d000
COLLAR (tool for YPVS)
This collar 1is used to remove and install the
push rod of the engine.
EC15e000
NIPPLE WRENCH
This nipple wrench 1is used to tighten the
spoke.
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
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.
1C3-9-32-1A 4/12/06 4:38 PM Page 26

1-12
GEN
INFO
FUEL AND ENGINE MIXING OIL
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:
Premium unleaded gasoline
only with a research octane
number of 95 or higher.
1C3-9-32-1B 4/5/06 5:26 PM Page 2

1-13
GEN
INFO
STARTING AND BREAK-IN
EC190000
STARTING AND BREAK-IN
cC
Before starting the machine, perform the
checks in the pre-operation check list.
w
Never start or run the engine in a closed
area. The exhaust fumes are poisonous;
they can cause loss of consciousness and
death in a very short time. Always operate
the machine in a well-ventilated area.
EC191001
STARTING A COLD ENGINE
1. Shift the transmission into neutral.
2. Turn the fuel cock to “ON” and full open the
starter knob (CHOKE).
3. With the throttle completely closed start the
engine by kicking the kick starter forcefully
with firm stroke.
4. Run the engine at idle or slightly higher until
it warms up: this usually takes about one or
two minutes.
5. The engine is warmed up when it responds
normally to the throttle with the starter knob
(CHOKE) turned off.
cC
Do not warm up the engine for extended peri-
ods.
EC193001
STARTING A WARM ENGINE
Do not operate the starter knob (CHOKE). Open
the throttle slightly and start the engine by kick-
ing the kick starter forcefully with firm stroke.
cC
Observe the following break-in procedures
during initial operation to ensure optimum
performance and avoid engine damage.
1C3-9-32-1B 4/5/06 5:26 PM Page 4