2010 YAMAHA YZ450F brake

2-14
TIGHTENING TORQUES
△Driven sprocket and wheel hub M8 × 1.25 6 42 4.2 30
△Nipple (spoke) — 72 3 0.3 2.2
△Disc cover and rear brake caliper M6 × 1.0 2 10 1.0 7.2
△Protector and rear brake caliper M6 × 1.0 2 7 0.7 5.1
Drive chain puller adjust bolt and locknut M8 × 1.25 2 21 2.1 15
Engine mounting:
△Upper engine bracket and frame M8 × 1.25 4 45 4.5 32
△Front engine bracket and frame M8 × 1.25 4 34 3.4 24
△Engine and engine bracket (front) M10 × 1.25 1 53 5.3 38
△Engine and engine bracket (upper) M10 × 1.25 2 45 4.5 32
△Engine and frame (lower) M10 × 1.25 1 53 5.3 38
△Engine guard M6 × 1.0 1 10 1.0 7.2
Lower engine guard M6 × 1.0 3 10 1.0 7.2
△Pivot shaft and nut M16 × 1.5 1 85 8.5 61
△Relay arm and swingarm M14 × 1.5 1 70 7.0 50
△Relay arm and connecting rod M14 × 1.5 1 80 8.0 58
△Connecting rod and frame M14 × 1.5 1 80 8.0 58
△Rear shock absorber and frame M10 × 1.25 1 56 5.6 40
△Rear shock absorber and relay arm M10 × 1.25 1 53 5.3 38
△Rear shock absorber locknut M60 × 1.5 1 30 3.0 22
△Rear frame and frame (upper) M8 × 1.25 1 32 3.2 23
△Rear frame and frame (lower) M8 × 1.25 2 32 3.2 23
△Swingarm and brake hose holder M5 × 0.8 4 3 0.3 2.2
Upper drive chain tensioner M8 × 1.25 1 16 1.6 11
Lower drive chain tensioner M8 × 1.25 1 16 1.6 11
Drive chain support and swingarm M6 × 1.0 3 7 0.7 5.1
△Seal guard and swingarm M5 × 0.8 3 4 0.4 2.9
△Fuel tank mounting boss and frame M10 × 1.25 1 20 2.0 14
△Fuel tank (front) M6 × 1.0 2 9 0.9 6.5
Fuel tank bracket (front) M6 × 1.0 4 7 0.7 5.1
△Fuel tank (rear) M6 × 1.0 2 9 0.9 6.5
Fuel tank bracket (rear) M6 × 1.0 2 7 0.7 5.1
△Fuel pump M5 × 0.8 6 4 0.4 2.9
Fuel tank side cover M6 × 1.0 4 7 0.7 5.1
Fuel tank and seat set bracket M6 × 1.0 1 7 0.7 5.1
Fuel tank and fuel tank bracket M6 × 1.0 4 7 0.7 5.1
Seat M8 × 1.25 2 22 2.2 16
△Side cover M6 × 1.0 4 7 0.7 5.1
Heat protector M5 × 0.8 2 4 0.4 2.9
△Air scoop and fuel tank M6 × 1.0 2 9 0.9 6.5
△Air scoop and air duct M6 × 1.0 2 7 0.7 5.1
radiator and radiator guard M6 × 1.0 2 10 1.0 7.2
△Air scoop and radiator guard M6 × 1.0 2 7 0.7 5.1
△Front fender M6 × 1.0 4 10 1.0 7.2Part to be tightened Thread size Q'tyTightening torque
Nm m•kg ft•lb

2-25
CABLE ROUTING DIAGRAM
1. Brake master cylinder
2. Brake hose holder
3. Brake hoseA. 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.

2-26
CABLE ROUTING DIAGRAM
1. Throttle cable
2. Clutch cable
3. Clamp
4. Engine stop switch lead
5. Hose guide
6. Main harnessA. Route the clutch cable to the
rear of the number plate band.
B. Fasten the engine stop switch
lead to the handlebar.
C. Route the brake hose to the
front of the number plate.
D. Pass the clutch cable through
the cable guide on the number
plate.

3-3
MAINTENANCE INTERVALS
AIR FILTER
Clean and lubricate●●Use foam air-filter oil or equivalent oil.
Replace●
OIL FILTER
Replace●●
ENGINE GUARD
Replace●Breakage
FRAME
Clean and inspect●●
FUEL TANK, FUEL PUMP
inspect●●
FUEL HOSE
Inspect●
Replace●Every four years
BRAKES
Adjust lever position and pedal
height●●
Lubricate pivot point●●
Check brake disc surface●●
Check fluid level and leakage●●
Retighten brake disc bolts, cali-
per bolts, master cylinder bolts
and union bolts●●
Replace pads●
Replace brake fluid●Every one year
FRONT FORKS
Inspect and adjust●●
Replace oil●●Suspension oil "S1"
Replace oil seal●
FRONT FORK OIL SEAL AND
DUST SEAL
Clean and lube●●Lithium base grease
PROTECTOR GUIDE
Replace●
REAR SHOCK ABSORBER
Inspect and adjust●●
Lube●(After
rain
ride)●Molybdenum disulfide grease
Retighten●●
DRIVE CHAIN GUIDE AND
ROLLERS
Inspect●● ItemAfter
break-
inEvery
race
(about
2.5
hours)
Every
third
(about
7.5
hours)Every
fifth
(about
12.5
hours)
As re-
quiredRemarks

3-5
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 MAINTENANCE
Item Routine Page
CoolantCheck that coolant is filled up to the radiator cap. Check the cool-
ing system for leakage.P.3-6 – 7
FuelCheck that a fresh gasoline is filled in the fuel tank. Check the fuel
line for leakage.P.1-17
Engine oilCheck that the oil level is correct. Check the crankcase and oil line
for leakage.P.3-9 – 10
Gear shifter and clutchCheck that gears can be shifted correctly in order and that the
clutch operates smoothly.P.3-7
Throttle grip/HousingCheck that the throttle grip operation and free play are correctly
adjusted. Lubricate the throttle grip and housing, if necessary.P.3-8
Brakes Check the play of front brake and effect of front and rear brake. P.3-14 – 17
Drive chainCheck drive chain slack and alignment. Check that the drive chain
is lubricated properly.P.3-17 –18
WheelsCheck for excessive wear and tire pressure. Check for loose
spokes and have no excessive play.P.3-21
SteeringCheck that the handlebar can be turned smoothly and have no ex-
cessive play.P.3-21 – 22
Front forks and rear shock
absorberCheck that they operate smoothly and there is no oil leakage.
P.3-18 – 20
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 – 6
Rear wheel sprocket Check that the rear wheel sprocket tightening bolt is not loose. P.3-17
Lubrication Check for smooth operation. Lubricate if necessary. P.3-23
Bolts and nuts Check the chassis and engine for loose bolts and nuts. P.1-19
Lead connectorsCheck that the AC magneto, ECU and ignition coil are connected
tightly.P.1-10 – 11
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.8-1 – 5

3-14
CHASSIS
CHASSIS
BLEEDING THE HYDRAULIC
BRAKE SYSTEM
Bleed the brake system if:
• The system has been disassem-
bled.
• A brake hose has been loosened
or removed.
• The brake fluid is very low.
• The brake operation is faulty.
A dangerous loss of braking per-
formance may occur if the brake
system is not properly bled.
1. Remove:
• Brake master cylinder cap
• Diaphragm
• Reservoir float (front brake)
• Protector (rear brake)
2. Bleed:
• Brake fluid
Air bleeding steps:
a. Add proper brake fluid to the res-
ervoir.
b. Install the diaphragm. Be careful
not to spill any fluid or allow the
reservoir to overflow.
c. Connect the clear plastic tube "2"
tightly to the caliper bleed screw
"1".
A. Front
B. Rear
d. Place the other end of the tube
into a container.
e. Slowly apply the brake lever or
pedal several times.
f. Pull the lever in or push down on
the pedal. Hold the lever or pedal
in position.
g. Loosen the bleed screw and allow
the lever or pedal to travel to-
wards its limit.h. Tighten the bleed screw when the
lever or pedal limit has been
reached; then release the lever or
pedal.
i. Repeat steps (e) to (h) until of the
air bubbles have been removed
from the system.
If bleeding is difficult, it may be nec-
essary to let the brake fluid system
stabilize for a few hours. Repeat the
bleeding procedure when the tiny
bubbles in the system have disap-
peared.
j. Add brake fluid to the level line on
the reservoir.
Check the operation of the brake
after bleeding the brake system.
3. Install:
• Protector (rear brake)
• Reservoir float (front brake)
• Diaphragm
• Brake master cylinder cap
ADJUSTING THE FRONT BRAKE
1. Check:
• Brake lever position "a"
2. Remove:
• Brake lever cover
3. Adjust:
• Brake lever position
Brake lever position adjustment
steps:
a. Loosen the locknut "1".b. Turn the adjusting bolt "2" until the
lever position "a" is within speci-
fied position.
c. Tighten the locknut.
Be sure to tighten the locknut, as it
will cause poor brake perfor-
mance.
4. Install:
• Brake lever cover
ADJUSTING THE REAR BRAKE
1. Check:
• Brake pedal height "a"
Out of specification→Adjust.
2. Adjust:
• Brake pedal height
Pedal height adjustment steps:
a. Loosen the locknut "1".
b. Turn the adjusting nut "2" until the
pedal height "a" is within specified
height.
• Adjust the pedal height between
the maximum "A" and the mini-
mum "B" as shown. (In this ad-
justment, the bolt "3" end "b"
should protrude out of the
threaded portion "4" but not be
less than 2 mm (0.08 in) "c" away
from the brake pedal "5").
• After the pedal height adjust-
ment, make sure that the rear
brake does not drag.
Bleed screw:
6 Nm (0.6 m•kg, 4.3
ft•lb)
Brake lever position "a":
Standard posi-
tionExtent of ad-
justment
95 mm (3.74 in)86–105 mm
(3.39–4.13 in)
Locknut:
5 Nm (0.5 m •kg, 3.6
ft•lb)
Brake pedal height "a":
Zero mm (Zero in)

3-15
CHASSIS
c. Tighten the locknut.
Be sure to tighten the locknut, as it
will cause poor brake perfor-
mance.
CHECKING AND REPLACING THE
FRONT BRAKE PADS
1. Inspect:
• Brake pad thickness "a"
Out of specification→Replace as
a set.
2. Replace:
• Brake pad
Brake pad replacement steps:
a. Remove the pad pin plug "1".b. Loosen the pad pin "2".
c. Remove the brake caliper "3"
from the front fork.
d. Remove the pad pin and brake
pads "4".
e. Connect the transparent hose "5"
to the bleed screw "6" and place
the suitable container under its
end.
f. Loosen the bleed screw and push
the brake caliper piston in.
Do not reuse the drained brake flu-
id.
g. Tighten the bleed screw.
h. Install the brake pads "7" and pad
pin.
• Install the brake pads with their pro-
jections "a" into the brake caliper re-
cesses "b".
• Temporarily tighten the pad pin at
this point.
i. Install the brake caliper "8" and
tighten the pad pin "9".
j. Install the pad pin plug "10".
3. Inspect:
• Brake fluid level
Refer to "CHECKING THE
BRAKE FLUID LEVEL" section.
4. Check:
• Brake lever operation
A softy or spongy feeling→Bleed
brake system.
Refer to "BLEEDING THE HY-
DRAULIC BRAKE SYSTEM" sec-
tion.
CHECKING AND REPLACING THE
REAR BRAKE PADS
1. Inspect:
• Brake pad thickness "a"
Out of specification→Replace as
a set. Locknut:
6 Nm (0.6 m •kg, 4.3
ft•lb)
Brake pad thickness:
4.4 mm (0.17 in)
: 1.0 mm (0.04
in)
Bleed screw:
6 Nm (0.6 m•kg, 4.3
ft•lb)
Bolt (brake caliper):
28 Nm (2.8 m•kg, 20
ft•lb)
Pad pin:
18 Nm (1.8 m•kg, 13
ft•lb)
Pad pin plug:
2 Nm (0.2 m•kg, 1.4
ft•lb)
Brake pad thickness:
6.4 mm (0.25 in)
: 1.0 mm (0.04
in)

3-16
CHASSIS
2. Replace:
• Brake pad
Brake pad replacement steps:
a. Remove the protector "1" and pad
pin plug "2".
b. Loosen the pad pin "3".
c. Remove the rear wheel "4" and
brake caliper "5".
Refer to "FRONT WHEEL AND
REAR WHEEL" section in the
CHAPTER 5.
d. Remove the pad pin "6" and brake
pads "7".
e. Connect the transparent hose "8"
to the bleed screw "9" and place
the suitable container under its
end.
f. Loosen the bleed screw and push
the brake caliper piston in.
Do not reuse the drained brake flu-
id.
g. Tighten the bleed screw.h. Install the brake pad "10" and pad
pin "11".
• Install the brake pads with their pro-
jections "a" into the brake caliper re-
cesses "b".
• Temporarily tighten the pad pin at
this point.
i. Install the brake caliper "12" and
rear wheel "13".
Refer to "FRONT WHEEL AND
REAR WHEEL" section in the
CHAPTER 5.
j. Tighten the pad pin "14".
k. Install the pad pin plug "15" and
protector "16".
3. Inspect:
• Brake fluid level
Refer to "CHECKING THE
BRAKE FLUID LEVEL" section.4. Check:
• Brake pedal operation
A softy or spongy feeling→Bleed
brake system.
Refer to "BLEEDING THE HY-
DRAULIC BRAKE SYSTEM" sec-
tion.
CHECKING THE REAR BRAKE
PAD INSULATOR
1. Remove:
• Brake pad
Refer to "CHECKING AND RE-
PLACING THE REAR BRAKE
PADS" section.
2. Inspect:
• Rear brake pad insulator "1"
Damage→Replace.
CHECKING THE BRAKE FLUID
LEVEL
1. Place the brake master cylinder
so that its top is in a horizontal po-
sition.
2. Inspect:
• Brake fluid level
Fluid at lower level→Fill up.
• Use only designated quality
brake fluid to avoid poor brake
performance.
• Refill with same type and brand
of brake fluid; mixing fluids
could result in poor brake perfor-
mance.
• Be sure that water or other con-
taminants do not enter master
cylinder when refilling.
• Clean up spilled fluid immediate-
ly to avoid erosion of painted
surfaces or plastic parts.
Bleed screw:
6 Nm (0.6 m•kg, 4.3
ft•lb)
Pad pin:
18 Nm (1.8 m•kg, 13
ft•lb)
Pad pin plug:
2 Nm (0.2 m•kg, 1.4
ft•lb)
Bolt (protector):
7 Nm (0.7 m•kg, 5.1
ft•lb)
Recommended brake flu-
id:
DOT #4