2008 YAMAHA YZ450F brake light

HOW TO READ DESCRIPTIONS
To help identify parts and clarify pro-
cedure steps, there are exploded dia-
grams at the start of each removal
and disassembly section.
1. An easy-to-see exploded diagram
"1" is provided for removal and
disassembly jobs.
2. Numbers "2" are given in the or-der of the jobs in the exploded di-
agram. A number that is enclosed
by a circle indicates a disassem-
bly step.
3. An explanation of jobs and notes
is presented in an easy-to-read
way by the use of symbol marks
"3". The meanings of the symbol
marks are given on the next page.4. A job instruction chart "4" accom-
panies the exploded diagram,
providing the order of jobs, names
of parts, notes in jobs, etc.
5. For jobs requiring more informa-
tion, the step-by-step format sup-
plements "5" are given in addition
to the exploded diagram and job
instruction chart.
ILLUSTRATED SYMBOLS (Refer to
the illustration)Illustrated symbols "1" to "7" are used
to identify the specifications appear-
ing in the text.
1. With engine mounted
2. Filling fluid
3. Lubricant
4. Special tool
5. Tightening
6. Specified value, Service limit
7. Resistance (
Ω), Voltage (V),
Electric current (A)
Illustrated symbols "8" to "13" in the
exploded diagrams indicate grade of
lubricant and location of lubrication
point.
8. Apply engine oil
9. Apply molybdenum disulfide oil
10. Apply brake fluid
11. Apply lightweight lithium-soap
base grease
12. Apply molybdenum disulfide
grease
13. Apply silicone grease
Illustrated symbols "14" to "15" in the
exploded diagrams indicate where to
apply a locking agent and where to in-
stall new parts.14. Apply locking agent (LOC-
TITE
®)
15. Use new one
1
23
45

1-1
DESCRIPTION
GENERAL INFORMATION
DESCRIPTION
• The machine you have purchased may differ slightly from those shown in the following.
• Designs and specifications are subject to change without notice.
1. Clutch lever
2. Hot starter lever
3. Front brake lever
4. Throttle grip
5. Radiator cap
6. Fuel tank cap
7. Engine stop switch
8. Kickstarter crank
9. Fuel tank
10. Radiator11. Coolant drain bolt
12. Rear brake pedal
13. Valve joint
14. Fuel cock
15. Cold starter knob
16. Drive chain
17. Air cleaner
18. Shift pedal
19. Oil dipstick
20. Front fork
1

1-8
CONTROL FUNCTIONS
CONTROL FUNCTIONS
ENGINE STOP SWITCH
The engine stop switch "1" is located
on the left handlebar. Continue push-
ing the engine stop switch till the en-
gine comes to a stop.
CLUTCH LEVER
The clutch lever "1" is located on the
left handlebar; it disengages or en-
gages the clutch. Pull the clutch lever
to the handlebar to disengage the
clutch, and release the lever to en-
gage the clutch. The lever should be
pulled rapidly and released slowly for
smooth starts.
SHIFT PEDAL
The gear ratios of the constant-mesh
5 speed transmission are ideally
spaced. The gears can be shifted by
using the shift pedal "1" on the left
side of the engine.
KICKSTARTER CRANK
Rotate the kickstarter crank "1" away
from the engine. Push the starter
down lightly with your foot until the
gears engage, then kick smoothly
and forcefully to start the engine. This
model has a primary kickstarter crank
so the engine can be started in any
gear if the clutch is disengaged. In
normal practices, however, shift to
neutral before starting.THROTTLE GRIP
The throttle grip "1" is located on the
right handlebar; it accelerates or de-
celerates the engine. For accelera-
tion, turn the grip toward you; for
deceleration, turn it away from you.
FRONT BRAKE LEVER
The front brake lever "1" is located on
the right handlebar. Pull it toward the
handlebar to activate the front brake.
REAR BRAKE PEDAL
The rear brake pedal "1" is located on
the right side of the machine. Press
down on the brake pedal to activate
the rear brake.
FUEL COCK
The fuel cock supplies fuel from the
tank to carburetor and also filters the
fuel. The fuel cock has the two posi-
tions:
OFF:
With the lever in this position, fuel will
not flow. Always return the lever to
this position 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.COLD STARTER KNOB
When cold, the engine requires a
richer air-fuel mixture for starting. A
separate starter circuit, which is con-
trolled by the cold starter knob "1",
supplies this mixture. Pull the cold
starter knob out to open the circuit for
starting. When the engine has
warmed up, push it in to close the cir-
cuit.
HOT STARTER LEVER
The hot starter lever "1" is used when
starting a warm engine. Use the hot
starter lever when starting the engine
again immediately after it was
stopped (the engine is still warm).
Pulling the hot starter lever injects
secondary air to thin the air-fuel mix-
ture temporarily, allowing the engine
to be started more easily.
STARTING AND BREAK-IN
FUEL
Always use the recommended fuel as
stated below. Also, be sure to use
new gasoline the day of a race.
Use only unleaded gasoline. The
use of leaded gasoline will cause
severe damage to the engine inter-
nal parts such as valves, piston
rings, and exhaust system, etc.
Recommended fuel:
Premium unleaded
gasoline only with a re-
search octane number
of 95 or higher.

1-12
CLEANING AND STORAGE
CLEANING AND STORAGE
CLEANING
Frequent cleaning of your machine
will enhance its appearance, maintain
good overall performance, and ex-
tend the life of many components.
1. Before washing the machine,
block off the end of the exhaust
pipe to prevent water from enter-
ing. A plastic bag secured with a
rubber band may be used for this
purpose.
2. If the engine is excessively
greasy, apply some degreaser to
it with a paint brush. Do not apply
degreaser to the chain, sprockets,
or wheel axles.
3. Rinse the dirt and degreaser off
with a garden hose; use only
enough pressure to do the job.
Excessive hose pressure may
cause water seepage and contami-
nation of wheel bearings, front
forks, brakes and transmission
seals. Many expensive repair bills
have resulted from improper high
pressure detergent applications
such as those available in coin-op-
erated car washers.
4. After the majority of the dirt has
been hosed off, wash all surfaces
with warm water and a mild deter-
gent. Use an old toothbrush to
clean hard-to-reach places.
5. Rinse the machine off immediate-
ly with clean water, and dry all
surfaces with a soft towel or cloth.
6. Immediately after washing, re-
move excess water from the
chain with a paper towel and lubri-
cate the chain to prevent rust.
7. Clean the seat with a vinyl uphol-
stery cleaner to keep the cover
pliable and glossy.
8. Automotive wax may be applied
to all painted or chromed surfac-
es. Avoid combination cleaner-
waxes, as they may contain abra-
sives.
9. After completing the above, start
the engine and allow it to idle for
several minutes.
STORAGE
If your machine is to be stored for 60
days or more, some preventive mea-
sures must be taken to avoid deterio-
ration. After cleaning the machine
thoroughly, prepare it for storage as
follows:
1. Drain the fuel tank, fuel lines, and the carburetor float bowl.
2. Remove the spark plug, pour a ta-
blespoon of SAE 10W-30 motor
oil in the spark plug hole, and re-
install the plug. With the engine
stop switch pushed in, kick the en-
gine over several times to coat the
cylinder walls with oil.
3. Remove the drive chain, clean it
thoroughly with solvent, and lubri-
cate it. Reinstall the chain or store
it in a plastic bag tied to the frame.
4. Lubricate all control cables.
5. Block the frame up to raise the
wheels off the ground.
6. Tie a plastic bag over the exhaust
pipe outlet to prevent moisture
from entering.
7. If the machine is to be stored in a
humid or salt-air environment,
coat all exposed metal surfaces
with a film of light oil. Do not apply
oil to rubber parts or the seat cov-
er.
Make any necessary repairs before
the machine is stored.

2-23
CABLE ROUTING DIAGRAM
1. Brake master cylinder
2. Brake hose holder
3. Brake hose
A. Install the brake hose so that its
pipe portion directs as shown
and lightly touches the projec-
tion on the brake caliper.
B. Pass the brake hose into the
brake hose holders.C. If the brake hose contacts the
spring (rear shock absorber),
correct its twist.
D. Install the brake hose so that its
pipe portion directs as shown
and lightly touches the projec-
tion on the brake master cylin-
der.

3-21
CHASSIS
LUBRICATION
To ensure smooth operation of all
components, lubricate your machine
during setup, after break-in, and after
every race.
1. All control cable
2. Clutch lever pivot
3. Shift pedal pivot
4. Footrest pivot
5. Throttle-to-handlebar contact
6. Drive chain
7. Tube guide cable winding por-
tion
8. Throttle cable end
9. Clutch cable end
10. Hot starter cable end
A. Use Yamaha cable lube or
equivalent on these areas.B. Use SAE 10W-30 motor oil or
suitable chain lubricants.
C. Lubricate the following areas
with high quality, lightweight lith-
ium-soap base grease.
Wipe off any excess grease, and
avoid getting grease on the brake
discs.

5-13
FRONT BRAKE AND REAR BRAKE
2. Install:
• Brake lever "1"
• Bolt (brake lever) "2"
• Nut (brake lever) "3"
Apply the silicone grease on the
brake lever sliding surface, bolt and
tip of the push rod.
INSTALLING THE REAR BRAKE
MASTER CYLINDER
1. Install:
• Copper washer "1"
• Brake hose "2"
• Union bolt "3"
Always use new copper washers.
Install the brake hose so that its
pipe portion "a" directs as shown
and lightly touches the projection
"b" on the brake master cylinder.
2. Install:
• Brake master cylinder "1"
• Bolt (brake master cylinder) "2"
3. Install:
• Spring "1"
• Brake pedal "2"
• O-ring "3"
• Bolt (brake pedal) "4"
• Clip "5"
Apply the lithium soap base grease
on the bolt, O-ring and brake pedal
bracket.
4. Install:
•Pin "1"
• Washer "2"
• Cotter pin "3"
After installing, check the brake pedal
height. Refer to "ADJUSTING THE
REAR BRAKE" section in the CHAP-
TER 3.
INSTALLING THE FRONT BRAKE
HOSE
1. Install:
• Copper washer "1"
• Brake hose "2"• Union bolt "3"
Always use new copper washers.
Install the brake hose so that its
pipe portion "a" directs as shown
and lightly touches the projection
"b" on the brake caliper.
2. Install:
• Brake hose holder "1"
• Nut (brake hose holder) "2"
Align the top "a" of the brake hose
holder with the paint "b" of the brake
hose.
3. Pass the brake hose through the
cable guide "1". Bolt (brake lever):
6 Nm (0.6 m•kg, 4.3
ft•lb)
Nut (brake lever):
6 Nm (0.6 m•kg, 4.3
ft•lb)
Union bolt:
30 Nm (3.0 m•kg, 22
ft•lb)
Bolt (brake master cylin-
der):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (brake pedal):
26 Nm (2.6 m•kg, 19
ft•lb)
Union bolt:
30 Nm (3.0 m•kg, 22
ft•lb)
Nut (brake hose holder):
7 Nm (0.7 m•kg, 5.1 ft
•lb)

5-14
FRONT BRAKE AND REAR BRAKE
4. Install:
• Copper washer "1"
• Brake hose "2"
• Union bolt "3"
Always use new copper washers.
Install the brake hose so that its
pipe portion "a" directs as shown
and lightly touches the projection
"b" on the brake master cylinder.
INSTALLING THE REAR BRAKE
HOSE
1. Install:
• Copper washer "1"
• Brake hose "2"
• Union bolt "3"
Always use new copper washers.
Install the brake hose so that its
pipe portion "a" directs as shown
and lightly touches the projection
"b" on the brake caliper.
2. Install:
• Brake hose holder "1"
• Screw (brake hose holder) "2"
After installing the brake hose
holders, make sure the brake hose
does not contact the spring (rear
shock absorber). If it does, correct
its twist.
FILLING THE BRAKE FLUID
1. Fill:
•Brake fluid
Until the fluid level reaches
"LOWER" level line "a".
• Use only the designated quality
brake fluid:
otherwise, the rubber seals may
deteriorate, causing leakage and
poor brake performance.
• Refill with the same type of brake
fluid;
mixing fluids may result in a
harmful chemical reaction and
lead to poor performance.
• Be careful that water does not
enter the master cylinder when
refilling. Water will significantly lower the boiling point of the flu-
id and may result in vapor lock.
Brake fluid may erode painted sur-
faces or plastic parts. Always
clean up spilled fluid immediately.
A. Front
B. Rear
2. Air bleed:
• Brake system
Refer to "BLEEDING THE HY-
DRAULIC BRAKE SYSTEM" sec-
tion in the CHAPTER 3.
3. Inspect:
• Brake fluid level
Fluid at lower level
→Fill up.
Refer to "CHECKING THE
BRAKE FLUID LEVEL" section in
the CHAPTER 3.
4. Install:
• Reservoir float (front brake)
• Diaphragm
• Brake master cylinder cap "1"
• Screw (brake master cylinder
cap) "2"
After installation, while pulling the
brake lever in or pushing down on
the brake pedal, check whether
there is any brake fluid leaking
where the union bolts are installed
respectively at the brake master
cylinder and brake caliper.
Union bolt:
30 Nm (3.0 m•kg, 22
ft•lb)
Union bolt:
30 Nm (3.0 m•kg, 22
ft•lb)
Screw (brake hose hold-
er):
2 Nm (0.2 m•kg, 1.4
ft•lb)
Recommended brake flu-
id:
DOT #4
Screw (bolt) {brake mas-
ter cylinder cap}:
2 Nm (0.2 m•kg, 1.4
ft•lb)