2008 YAMAHA YZ450F radiator

2-20
CABLE ROUTING DIAGRAM
1. Hot starter cable
2. Clamp
3. Throttle position sensor lead
4. Hump (frame)
5. Neutral switch lead
6. Engine bracket
7. Lower engine guard stay
8. CDI magneto lead
9. Clutch cable
10. Radiator breather hose
11. Radiator hose 212. Engine stop switch lead
13. Sub-wire harness
14. Ground lead
15. CDI unit bracket
16. CDI unit
17. Cable guide
18. Ignition coil lead
19. Throttle cableA. Fasten the hot starter cable and
throttle cables onto the frame.
Locate the clamp ends under
the hot starter cable.
B. Fasten the hot starter cable,
throttle cables, throttle position
sensor lead and ignition coil lead
to the frame.
C. Pass the throttle position sensor
lead over the hot starter cable.

2-21
CABLE ROUTING DIAGRAM
D. Fasten the throttle position sen-
sor lead to the frame behind its
hump.
E. Pass the neutral switch lead on
the inside of the engine bracket.
F. Pass the neutral switch lead
over the lower engine guard
stay.
G. Fasten the neutral switch lead
and radiator breather hose to
the frame.
H. Fasten the neutral switch lead,
CDI magneto lead and radiator
breather hose to the frame.
I. Fasten the neutral switch lead,
CDI magneto lead, radiator
breather hose and clutch cable
to the frame over the radiator
mounting boss.
J. Pass the radiator breather hose
in front of the radiator hose 2, on
the left of the chassis, and then
between the frame and radiator
hose 4.
K. Fasten the sub-wire harness,
engine stop switch lead and
ground lead to the CDI unit
bracket at the position-taped
portion of the sub-wire harness
and with the clamp ends facing
downward.
L. Fasten the ground lead and ca-
ble guide together to the CDI
unit bracket.
M. Locate the clamp ends in the ar-
rowed range.
N. Fasten the neutral switch lead
and CDI magneto lead to the
frame over its hump.

2-22
CABLE ROUTING DIAGRAM
1. Throttle cable (pull)
2. Throttle cable (return)
3. Radiator hose 2
4. Ignition coil
5. Rear arm bracket
6. Cylinder head breather hose
A. Pass the throttle cables over the
radiator hose 2.
B. Pass the throttle cables on the
outside of the ignition coil.C. Fasten the throttle cables with
the clamp so that the cables are
not bent, and pass them under
the rear arm bracket.
D. Pass the cylinder head breather
hose so that it does not contact
the ignition coil.

3-2
MAINTENANCE INTERVALS
Replace●
TRANSMISSION
Inspect
●
Replace bearing●
SHIFT FORK, SHIFT CAM,
GUIDE BAR
Inspect
●Inspect wear.
ROTOR NUT
Retighten
●●
EXHAUST PIPE, SILENCER,
PROTECTOR
Inspect and retighten
●●
Clean●
Replace●* Whichever comes first
CRANK
Inspect and clean
●●
CARBURETOR
Inspect, adjust and clean
●●
SPARK PLUG
Inspect and clean
●●
Replace●
DRIVE CHAIN Use chain lube.
Lubricate, slack, alignment
●●Chain slack: 48–58 mm (1.9–2.3 in)
Replace
●
COOLING SYSTEM
Check coolant level and leakage
●●
Check radiator cap operation●
Replace coolant●Every two years
Inspect hoses
●
OUTSIDE NUTS AND BOLTS
Retighten
●●Refer to "STARTING AND BREAK-
IN" section in the CHAPTER 1.
AIR FILTER
Clean and lubricate
●●Use foam air-filter oil or equivalent oil.
Replace
●
OIL FILTER
Replace
●●
FRAME
Clean and inspect
●●
FUEL TANK, COCK
Clean and inspect
●●
BRAKES
Adjust lever position and pedal
height
●●
ItemAfter
break-
inEvery
race
Every
third
(or 500
km)Every
fifth (or
1,000
km)
As re-
quiredRemarks

3-4
PRE-OPERATION INSPECTION AND MAINTENANCE
PRE-OPERATION INSPECTION AND MAINTENANCE
Before riding for break-in operation, practice or a race, make sure the machine is in good operating condition.
Before using this machine, check the following points.
GENERAL INSPECTION AND MAINTENANCETHROTTLE, CONTROL CABLE
Check routing and connection
●●Yamaha cable lube or SAE 10W-30
motor oil
Lubricate
●●
HOT STARTER, CLUTCH LEVER
Inspect free play
●
ItemAfter
break-
inEvery
race
Every
third
(or 500
km)Every
fifth (or
1,000
km)
As re-
quiredRemarks
Item Routine Page
CoolantCheck that coolant is filled up to the radiator cap. Check the cool-
ing system for leakage.P.3-5 – 6
FuelCheck that a fresh gasoline is filled in the fuel tank. Check the fuel
line for leakage.P.1-8
Engine oilCheck that the oil level is correct. Check the crankcase and oil line
for leakage.P.3-8 – 9
Gear shifter and clutchCheck that gears can be shifted correctly in order and that the
clutch operates smoothly.P.3-6
Throttle grip/HousingCheck that the throttle grip operation and free play are correctly
adjusted. Lubricate the throttle grip and housing, if necessary.P.3-6 – 7
Brakes Check the play of front brake and effect of front and rear brake. P.3-13 – 15
Drive chainCheck drive chain slack and alignment. Check that the drive chain
is lubricated properly.P.3-16
WheelsCheck for excessive wear and tire pressure. Check for loose
spokes and have no excessive play.P.3-19
SteeringCheck that the handlebar can be turned smoothly and have no ex-
cessive play.P.3-19 – 20
Front forks and rear shock
absorberCheck that they operate smoothly and there is no oil leakage.
P.3-17 – 19
Cables (wires)Check that the clutch and throttle cables move smoothly. Check
that they are not caught when the handlebars are turned or when
the front forks travel up and down.—
Exhaust pipe Check that the exhaust pipe is tightly mounted and has no cracks. P.4-3 – 4
Rear wheel sprocket Check that the rear wheel sprocket tightening bolt is not loose. P.3-15 – 16
Lubrication Check for smooth operation. Lubricate if necessary. P.3-21
Bolts and nuts Check the chassis and engine for loose bolts and nuts. P.1-11
Lead connectorsCheck that the CDI magneto, CDI unit, and ignition coil are con-
nected tightly.P.1-3
SettingsIs the machine set suitably for the condition of the racing course
and weather or by taking into account the results of test runs be-
fore racing? Are inspection and maintenance completely done?P.7-1 – 10

3-5
ENGINE
ENGINE
CHECKING THE COOLANT LEVEL
Do not remove the radiator cap
"1", drain bolt and hoses when the
engine and radiator are hot. Scald-
ing hot fluid and steam may be
blown out under pressure, which
could cause serious injury. When
the engine has cooled, place a
thick towel over the radiator cap,
slowly rotate the cap counter-
clockwise to the detent. This pro-
cedure allows any residual
pressure to escape. When the
hissing sound has stopped, press
down on the cap while turning
counterclockwise and remove it.
Hard water or salt water is harmful
to the engine parts. You may use
distilled water, if you can't get soft
water.
1. Place the machine on a level
place, and hold it in an upright po-
sition.
2. Remove:
• Radiator cap
3. Check:
• Coolant level "a"
Coolant level low
→Add coolant.
1. Radiator
CHANGING THE COOLANT
Do not remove the radiator cap
when the engine is hot.
Take care so that coolant does not
splash on painted surfaces. If it
splashes, wash it away with water.
1. Place a container under the en-gine.
2. Remove:
• Engine guard "1"
• Coolant drain bolt "2"
3. Remove:
• Radiator cap
Drain the coolant completely.
4. Clean:
• Cooling system
Thoroughly flush the cooling sys-
tem with clean tap water.
5. Install:
• Copper washer
• Coolant drain bolt
• Engine guard
• Bolt (engine guard)
6. Fill:
• Radiator
•Engine
To specified level.
• Do not mix more than one type of
ethylene glycol antifreeze con-
taining corrosion inhibitors for
aluminum engine.
• Do not use water containing im-
purities or oil.
Handling notes of coolant:
The coolant is harmful so it should be
handled with special care.
• When coolant splashes to your
eye.
Thoroughly wash your eye with
water and see your doctor.
• When coolant splashes to your
clothes.
Quickly wash it away with water
and then with soap.
• When coolant is swallowed.
Quickly make him vomit and take
him to a doctor.
7. Install:
• Radiator cap
Start the engine and warm it up
for a several minutes.
8. Check:
• Coolant level
Coolant level low
→Add coolant.
CHECKING THE RADIATOR CAP
1. Inspect:
• Seal (radiator cap) "1"
• Valve and valve seat "2"
Crack/damage
→Replace.
Exist fur deposits "3"
→Clean or
replace.
CHECKING THE RADIATOR CAP
OPENING PRESSURE
1. Attach:
• Radiator cap tester "1" and adapt-
er "2"
Coolant drain bolt:
10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (engine guard):
10 Nm (1.0 m•kg, 7.2
ft•lb)
Recommended coolant:
High quality ethylene
glycol anti-freeze con-
taining anti-corrosion
for aluminum engine
Coolant "1" and water
(soft water) "2" mixing ra-
tio:
50%/50%
Coolant capacity:
0.99 L (0.87 Imp qt, 1.05
US qt)
Radiator cap tester:
YU-24460-01/90890-
01325
Radiator cap tester
adapter:
YU-33984/90890-01352

3-6
ENGINE
Apply water on the radiator cap seal.
3. Radiator cap
2. Apply the specified pressure.
3. Inspect:
• Pressure
Impossible to maintain the speci-
fied pressure for 10 seconds
→
Replace.
CHECKING THE COOLING
SYSTEM
1. Inspect:
• Coolant level
2. Attach:
• Radiator cap tester "1" and adapt-
er "2"
3. Apply the specified pressure.
• Do not apply pressure more than
specified pressure.
• Radiator should be filled fully.
4. Inspect:
• Pressure
Impossible to maintain the speci-
fied pressure for 10 seconds
→
Repair.
•Radiator
• Radiator hose joint
Coolant leakage
→Repair or re-place.
• Radiator hose
Swelling
→Replace.
ADJUSTING THE CLUTCH CABLE
FREE PLAY
1. Check:
• Clutch lever free play "a"
Out of specification
→Adjust.
2. Adjust:
• Clutch lever free play
Clutch lever free play adjustment
steps:
a. Loosen the locknuts "1".
b. Turn the adjuster "2" until free
play "a" is within the specified lim-
its.
c. Tighten the locknuts.
• Before adjustment, expose the ad-
juster by moving the boot "3" and
cap "4" away.
• Make minute adjustment on the le-
ver side using the adjuster "5".
• After adjustment, check proper op-
eration of clutch lever.
3. Install:
• Cap "1"
•Boot "2"
Place the tip "a" of the cap in the boot.
ADJUSTING THE THROTTLE
CABLE FREE PLAY
1. Check:
• Throttle grip free play "a"
Out of specification
→Adjust.
2. Adjust:
• Throttle grip free play
Throttle grip free play adjustment
steps:
a. Slide the adjuster cover.
b. Loosen the locknut "1".
c. Turn the adjuster "2" until the
specified free play is obtained.
d. Tighten the locknut.
Before adjusting the throttle cable
free play, the engine idle speed
should be adjusted.
After adjusting the throttle cable
free play, start the engine and turn
the handlebar to right and left and
make sure that the engine idling
does not run faster.
Radiator cap opening
pressure:
110 kPa (1.1 kg/cm
2,
15.6 psi)
Radiator cap tester:
YU-24460-01/90890-
01325
Radiator cap tester
adapter:
YU-33984/90890-01352
Standard pressure:
180 kPa (1.8 kg/cm
2,
25.6 psi)
Clutch lever free play "a"
:
8–13 mm (0.31–0.51 in)
Locknut:
4 Nm (0.4 m•kg, 2.9
ft•lb)
Throttle grip free play
"a":
3–5 mm (0.12–0.20 in)
Locknut:
4 Nm (0.4 m•kg, 2.9
ft•lb)

4-5
RADIATOR
RADIATOR
REMOVING THE RADIATOR
Order Part name Q'ty Remarks
Drain the coolant.Refer to "CHANGING THE COOLANT" sec-
tion in the CHAPTER 3.
Seat and fuel tankRefer to "SEAT, FUEL TANK AND SIDE
COVERS" section.
Exhaust pipeRefer to "EXHAUST PIPE AND SILENCER"
section.
1 Radiator guard 2
2 Radiator hose clamp 8 Only loosening.
3 Right radiator 1
4 Radiator hose 2 1
5 Radiator hose 3 1
6 Radiator hose 4 1
7 Pipe 2/O-ring 1/1
8 Radiator breather hose 1
9 Left radiator 1
10 Radiator hose 1 1
11 Pipe 1/O-ring 1/1