YAMAHA YZ450F 2015 Owners Manual

FRONT BRAKE
4-15
EAS1SL5137INTRODUCTIONEWA14100
WARNING
If you need to disassemble the disc brake
components, observe the following precau-
tions.
• Never disassemble the brake components
unless absolutely necessary.
• If there is any problem with connections
on the hydraulic brake system, perform
the following jobs.
Disassemble the brake system, drain the
brake fluid, and clean it. After that, add a
suitable amount of brake fluid. Then, bleed
it after reassembly.
• Use only brake fluid for washing brake
components.
• Use new brake fluid for cleaning the brake
components.
• Immediately wipe off the spilled brake fluid
to avoid damage to painted surfaces or
plastic parts.
• Handle brake fluid with special care not to
let it enter your eyes so that you may not
lost your eyesight.
• FIRST AID FOR BRAKE FLUID ENTERING
THE EYES:
• Flush with water for 15 minutes and get
immediate medical attention.
EAS1SL5138CHECKING THE FRONT BRAKE DISC
1. Remove:
• Front wheel
Refer to “FRONT WHEEL” on page 4-3.
2. Check:
• Front brake disc
Damage/galling  Replace.
3. Measure:
• Brake disc thickness
Measure the brake disc thickness at a few
different locations.
Out of specification  Replace.4. Install:
• Front wheel
Refer to “FRONT WHEEL” on page 4-3.
EAS1SL5139REMOVING THE FRONT BRAKE CALIPER
TIP
Before disassembling the brake caliper, drain
the brake fluid from the entire brake system.
1. Remove:
• Union bolt
• Copper washers
• Brake hose
TIP
Put the end of the brake hose into a container
and pump out the brake fluid.
EAS1SL5140DISASSEMBLING THE FRONT BRAKE CAL-
IPER
1. Remove:
• Brake caliper piston “1”
• Brake caliper piston dust seal “2”
• Brake caliper piston seals “3”Brake disk thickness limit
2.5 mm (0.10 in)
3
2
1

FRONT BRAKE
4-16
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Blow compressed air into the brake hose
joint opening to force out the piston from the
brake caliper.
EWA13550
WARNING
• Cover the brake caliper piston with a rag.
Be careful not to get injured when the pis-
ton is expelled from the brake caliper.
• Never try to pry out the brake caliper pis-
ton.
b. Remove the brake caliper piston dust seal
and the brake caliper piston seal.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
EAS1SL5141CHECKING THE FRONT BRAKE CALIPER
1. Check:
• Brake caliper piston “1”
Rust/scratches/wear  Replace the brake
caliper piston.
• Brake caliper cylinder “2”
Scratches/wear  Replace the brake cali-
per assembly.
• Brake caliper body “3”
Cracks/damage  Replace the brake cali-
per assembly.
• Brake fluid delivery passages
(brake caliper body)
Obstruction  Blow out with compressed
air.
EWA13600
WARNING
When the brake caliper is disassembled, re-
place the brake caliper piston seal and the
brake caliper piston dust seal with new
ones.
2. Check:
• Brake caliper bracket
Crack/damage  Replace.
EAS1SL5142ASSEMBLING THE FRONT BRAKE CALI-
PER
EWA13620
WARNING
• Before installation, clean and lubricate the
internal parts. Use new brake fluid for
cleaning and lubricating.
• Never use solvents on internal brake com-
ponents as they will cause the piston seals
to swell and distort.
• When the brake caliper is disassembled,
replace the brake caliper piston seal and
the brake caliper piston dust seal with new
ones.
EAS1SL5143INSTALLING THE BRAKE CALIPER PISTON
1. Clean:
• Brake caliper
• Brake caliper piston seal
• Brake caliper piston dust seal
• Brake caliper piston
Use brake fluid for cleaning.
2. Install:
• Brake caliper piston seals “1”
• Brake caliper piston dust seal “2”
EWA33DD033
WARNING
Always use new brake caliper piston seal
and brake caliper piston dust seal.
TIP
• Apply the silicone grease on the brake caliper
piston seal and brake caliper piston dust seal.
• Fit the brake caliper piston seal and the brake
caliper piston dust seal into the grooves in the
brake caliper correctly.
2
113
Recommended brake fluid
DOT 4
New
New

FRONT BRAKE
4-17
3. Install:
• Brake caliper piston “1”
TIP
Apply the brake fluid on the piston outer sur-
face.
ECA33DD047
NOTICE
• Install the piston with its side “a” facing
the brake caliper.
• Never force to insert.
EAS1SL5144INSTALLING THE FRONT BRAKE CALIPER
1. Install:
• Front brake caliper bracket
• Front brake caliper
(temporarily)
• Copper washers
• Brake hose
• Union bolt
EWA13530
WARNING
Proper brake hose routing is essential to in-
sure safe vehicle operation.
ECA14170
NOTICE
Make sure that the pipe portion “a” of the
brake hose touches the projection “b” on
the brake caliper.
2. Install:
• Front brake caliper
• Brake pad spring
• Brake pad
• Brake pad pin
• Brake hose holder
Refer to “CHECKING THE FRONT BRAKE
PADS” on page 3-23.
3. Tighten:
• Brake hose holder mounting bolt “1”
TIP
Make sure that the brake hose holder “2” is in-
stalled with its upper end “a” aligned with the
paint “b” on the brake hose.
4. Pour brake fluid to the brake master cylinder
reservoir up to the specified level.
EWA13090
Front brake caliper bracket
28 Nm (2.8 m·kgf, 20 ft·lbf)
Brake hose union bolt
30 Nm (3.0 m·kgf, 22 ft·lbf)
1
1
22
1
a
1
New
T R..
Brake pad pin
17 Nm (1.7 m·kgf, 12 ft·lbf)
Brake hose holder mounting bolt
9 Nm (0.9 m·kgf, 6.5 ft·lbf)
Recommended brake fluid
DOT 4
a
b
T R..
T R..
2
1 b
a

FRONT BRAKE
4-18
WARNING
• Use only the designated brake fluid. Other
brake fluids may cause the rubber seals to
deteriorate, causing leakage and poor
brake performance.
• Refill with the same type of brake fluid that
is already in the system. Mixing brake flu-
ids may result in a harmful chemical reac-
tion, leading to poor brake performance.
• When refilling, be careful that water does
not enter the brake fluid reservoir. Water
will significantly lower the boiling point of
the brake fluid and could cause vapor
lock.
ECA13540
NOTICE
Brake fluid may damage painted surfaces
and plastic parts. Therefore, always clean
up any spilt brake fluid immediately.
5. Bleed:
• Brake system
Refer to “BLEEDING THE BRAKE SYS-
TEM” on page 3-21.
6. Check:
• Brake fluid level
The minimum level mark or below  Add.
Refer to “CHECKING THE BRAKE FLUID
LEVEL” on page 3-26.
7. Check:
• Brake lever free play
Refer to “ADJUSTING THE FRONT
BRAKE” on page 3-22.
• Brake lever operation
A softy or spongy feeling  Bleed the brake
system.
Refer to “BLEEDING THE BRAKE SYS-
TEM” on page 3-21.
EAS1SL5145REMOVING THE FRONT BRAKE MASTER
CYLINDER
TIP
Before removing the front brake master cylin-
der, drain the brake fluid from the entire brake
system.
1. Remove:
• Union bolt
• Copper washers
• Brake hoses
TIP
To drain any remaining brake fluid, place a con-
tainer under the master cylinder and the end of
the brake hose.
EAS1SL5146CHECKING THE FRONT BRAKE MASTER
CYLINDER
1. Check:
• Brake master cylinder “1”
Damage/scratches/wear  Replace.
• Brake fluid delivery passages “2”
(brake master cylinder body)
Obstruction  Blow out with compressed
air.
2. Check:
• Brake master cylinder kit
Damage/scratches/wear  Replace.
3. Check:
• Brake master cylinder reservoir cap
4. Check:
• Brake hoses
Cracks/damage/wear  Replace.
EAS1SL5147ASSEMBLING THE FRONT BRAKE MAS-
TER CYLINDER
EWA13520
WARNING
• Before installation, all internal brake com-
ponents should be cleaned and lubricated
with clean or new brake fluid.
• Never use solvents on internal brake com-
ponents.
1. Wash the brake master cylinder and the
brake master cylinder kit with brake fluid.
2. Install:
• Primary cylinder cup “1”
• Secondary cylinder cup “2”
Install to the brake master cylinder piston
“3”.
EWA13520
Recommended brake fluid
DOT 4
1
2

FRONT BRAKE
4-19
WARNING
Apply brake fluid to the cylinder cups and
install them as shown. Wrong orientation in
installation causes poor braking perfor-
mance.
3. Install:
• Spring “1”
Install to the brake master cylinder piston
“2”.
TIP
Install the spring with a smaller inside diameter
to the brake master cylinder piston.
4. Install:
• Brake master cylinder kit “1”
• Washer “2”
• Circlip “3”
• Dust boot “4”
• Push rod “5”
TIP
• Before installation, apply brake fluid to the
brake master cylinder kit.
• Before installation, apply silicone grease to
the push rod end.
• Use circlip pliers to install the circlip.
EAS1SL5148INSTALLING THE FRONT BRAKE MASTER
CYLINDER
1. Install:
• Brake master cylinder “1”
TIP
• Install the front brake master cylinder holder
with the “UP” mark facing up.
• First, tighten the upper bolt, then the lower
bolt.
2. Install:
• Copper washers
• Brake hose
• Union bolt
EWA13530
12
3
2 1
3
New
New
Brake master cylinder holder bolt
9 Nm (0.9 m·kgf, 6.5 ft·lbf)
Brake hose union bolt
30 Nm (3.0 m·kgf, 22 ft·lbf)
T R..
New
T R..

FRONT BRAKE
4-20
WARNING
Proper brake hose routing is essential to in-
sure safe vehicle operation.
ECA1DX1007
NOTICE
During installation, bring the brake hose
into contact with the brake master cylinder
projection “a” and make its bent portion “b”
face downward.
TIP
Turn the handlebar toward right and left to
make sure that the brake hose does not touch
other parts (e.g., wire harness, cables, leads).
Adjust if necessary.
3. Pour brake fluid to the brake master cylinder
reservoir up to the specified level.
EWA13540
WARNING
• Use only the designated brake fluid. Other
brake fluids may cause the rubber seals to
deteriorate, causing leakage and poor
brake performance.
• Refill with the same type of brake fluid that
is already in the system. Mixing brake flu-
ids may result in a harmful chemical reac-
tion, leading to poor brake performance.
• When refilling, be careful that water does
not enter the brake master cylinder reser-
voir. Water will significantly lower the boil-
ing point of the brake fluid and could
cause vapor lock.
ECA13540
NOTICE
Brake fluid may damage painted surfaces
and plastic parts. Therefore, always clean
up any spilt brake fluid immediately.4. Bleed:
• Brake system
Refer to “BLEEDING THE BRAKE SYS-
TEM” on page 3-21.
5. Check:
• Brake fluid level
The minimum level mark “a” or below 
Add.
Refer to “CHECKING THE BRAKE FLUID
LEVEL” on page 3-26.
6. Check:
• Brake lever free play
Refer to “ADJUSTING THE FRONT
BRAKE” on page 3-22.
• Brake lever operation
A softy or spongy feeling  Bleed the brake
system.
Refer to “BLEEDING THE BRAKE SYS-
TEM” on page 3-21.
Recommended brake fluid
DOT 4

REAR BRAKE
4-21
EAS1SL5149
REAR BRAKE
Removing the rear brake caliper
Order Part name Q’ty Remarks
Brake fluidDrain.
Refer to “BLEEDING THE BRAKE SYSTEM”
on page 3-21.
1 Protector 1
2 Union bolt 1
3 Copper washers 2
4 Rear brake hose 1
5 Brake pad pin plug 1
6 Brake pad pin 1
7 Rear brake pad assembly 2
8 Rear brake caliper bracket 1
9 Brake pad springs 2
10 Rear brake disc cover 1
11 Rear brake caliper assembly 1
For installation, reverse the removal proce-
dure.
2
3
4 11
56
79
1
8
9 10
2.5 Nm (0.25 m•kgf, 1.8 ft•Ibf)T.R.
10 Nm (1.0 m•kgf, 7.2 ft•Ibf)T.R.
10 Nm (1.0 m•kgf, 7.2 ft•Ibf)T.R.
17 Nm (1.7 m•kgf, 12 ft•Ibf)T.R.
30 Nm (3.0 m•kgf, 22 ft•Ibf)T.R.
New
S
7 Nm (0.7 m•kgf, 5.1 ft•Ibf)T.R.

REAR BRAKE
4-22
Disassembling the rear brake caliper
Order Part name Q’ty Remarks
1 Brake caliper piston 1
2 Brake caliper piston dust seal 1
3 Brake caliper piston seal 1
4 Bleed screw 1
For assembly, reverse the disassemble pro-
cedure.
1
2
3
4
S
BF
T R..6 Nm (0.6 m kgf, 4.3 ft Ibf)

REAR BRAKE
4-23
Removing the rear brake master cylinder
Order Part name Q’ty Remarks
Brake fluidDrain.
Refer to “BLEEDING THE BRAKE SYSTEM”
on page 3-21.
1 Union bolt 1
2 Copper washers 2
3 Brake hose 1
4 Split pin 1
5Washer 1
6Pin 1
7 Brake master cylinder reservoir cap 1
8 Brake master cylinder reservoir diaphragm plate 1
9 Brake master cylinder reservoir diaphragm 1
10 Rear brake master cylinder 1
For installation, reverse the removal proce-
dure.
1
2
3
4 7
5 8
6 9
T R..
T R..
10
T R..

REAR BRAKE
4-24
Disassembling the rear brake master cylinder
Order Part name Q’ty Remarks
1 Dust boot 1
2 Circlip 1
3 Push rod 1
4 Brake master cylinder kit 1
For assembly, reverse the disassemble pro-
cedure.
4
3
2
1
BF
S
New
New