2016 YAMAHA WR 450F Owners Manual

REAR BRAKE
5-25
Removing the rear brake master cylinder
OrderPart name Q’tyRemarks
Brake fluid Drain.
Refer to “BLEEDING THE BRAKE SYSTEM”
on page 3-25.
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
5-26
Disassembling the rear brake master cylinder
OrderPart name Q’tyRemarks
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

REAR BRAKE
5-27
EAS2GC1181INTRODUCTIONEWA
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 internal
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.
EAS2GC1182CHECKING THE REAR BRAKE DISC
1. Remove: • Rear wheel
Refer to “REAR WHEEL” on page 5-9.
2. Check: • Brake disc
Damage/galling  Replace.
3. Measure: • Brake disc thickness
Measure the brake disc thickness at a few
different locations.
Out of specification  Replace.
Refer to “CHECKING THE FRONT BRAKE
DISC” on page 5-17.
4. Measure: • Brake disc deflection
Out of specification  Correct the brake disc
deflection or replace the brake disc. 5. Adjust:
• Brake disc deflection
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Remove the brake disc.
b. Turn the mounted position of the brake disc by one bolt hole.
c. Install the brake disc.
TIP
Tighten the brake disc bolts in stages and in a
crisscross pattern.
d. Measure the brake disc deflection.
e. If out of specification, repeat the adjustment steps until the brake disc deflection is within
specification.
f. If the brake disc deflection cannot be
brought within specification, replace the
brake disc.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
6. Install:• Rear wheel
Refer to “REAR WHEEL” on page 5-9.
Brake disc thickness limit
3.5 mm (0.14 in)
Brake disc runout limit (as mea-
sured on wheel) 0.15 mm (0.0059 in)
Brake disc bolt 14 Nm (1.4 m·kgf, 10 ft·lbf)
LOCTITE®
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REAR BRAKE
5-28
EAS2GC1183REMOVING THE REAR 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.
EAS2GC1184DISASSEMBLING THE REAR BRAKE CALI-
PER
1. Remove:
• Brake caliper piston “1”
• Brake caliper piston dust seal “2”
• Brake caliper piston seal “3”
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Blow compressed air into the brake hose joint opening to force out the piston from the
brake caliper.
EWA
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.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
EAS2GC1185CHECKING THE REAR 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.
EWA
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.
EAS2GC1186ASSEMBLING THE REAR BRAKE CALIPEREWA
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.
2 3
1
Specified brake fluid
DOT 4
1
2
3

REAR BRAKE
5-29
EAS2GC1187INSTALLING THE BRAKE CALIPER PISTON
1. Clean:• Brake caliper
• Brake caliper piston seal
• Brake caliper piston dust seal
• Brake caliper pistonUse brake fluid for cleaning.
2. Install: • Brake caliper piston seals “1”
• Brake caliper piston dust seal “2”
EWA
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 seals and brake caliper piston dust seals onto the slot on
brake caliper correctly.
3. Install: • Brake caliper piston “1”
TIP
Apply the brake fluid on the piston outer sur-
face.
ECA
NOTICE
• Install the piston with its side “a” facing the brake caliper.
• Never force to insert.
EAS2GC1188INSTALLING THE REAR BRAKE CALIPER
1. Install:
• Rear brake caliper
• Rear brake caliper bracket
2. Install: • Rear wheelRefer to “REAR WHEEL” on page 5-9.
• Copper washers
• Brake hose
• Union bolt
EWA
WARNING
Proper brake hose routing is essential to in-
sure safe vehicle operation.
ECA
NOTICE
Make sure that a bend in its pipe portion “a”
is directed as shown and the brake hose
touches the projection “b” on the brake cal-
iper.
3. Install: • Brake pad springs
• Brake pads
• Brake pad pin
• Brake pad pin plug
Refer to “CHECKING THE REAR BRAKE
PADS” on page 3-29.
4. Pour brake fluid to the brake fluid reservoir up to the specified level.
EWA
New
New
2
1
1
a1
Brake hose union bolt
30 Nm (3.0 m·kgf, 22 ft·lbf)
Brake pad pin 17 Nm (1.7 m·kgf, 12 ft·lbf)
Brake pad pin plug 2.5 Nm (0.25 m·kgf, 1.8 ft·lbf)
Specified brake fluid DOT 4
New
T R..
b
b a
T R..

REAR BRAKE
5-30
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.
ECA
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 3-25.
6. Check:
• Brake fluid levelThe minimum level mark “a” or below 
Add.
Refer to “CHECKING THE BRAKE FLUID
LEVEL” on page 3-30.
7. Check: • Brake pedal operationA softy or spongy feeling  Bleed the brake
system.
Refer to “BLEEDING THE BRAKE SYS-
TEM” on page 3-25.
EAS2GC1189REMOVING THE REAR BRAKE MASTER
CYLINDER
TIP
Before removing the rear brake master cylin-
der, drain the brake fluid from the entire brake
system. 1. Remove:
• Union bolt
• Copper washers
• Brake hose
TIP
To drain any remaining brake fluid, place a con-
tainer under the master cylinder and the end of
the brake hose.
EAS2GC1190CHECKING THE REAR 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/wear  Replace.
3. Check: • Master cylinder reservoir capCrack/damage  Replace.
• Brake master cylinder reservoir diaphragm holder
• Brake master cylinder reservoir diaphragm
Crack/damage  Replace.
4. Check: • Brake hoses
Cracks/damage/wear  Replace.
EAS2GC1191ASSEMBLING THE REAR BRAKE MASTER
CYLINDER
EWA
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.
a
1 2

REAR BRAKE
5-31
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”.
EWA
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:
• Master cylinder kit “1”
• Push rod “2”
• Circlip “3”
• Dust boot “4”
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.
EAS2GC1192INSTALLING THE REAR BRAKE MASTER
CYLINDER
1. Install:• Copper washers
• Brake hose
• Union bolt
EWA
WARNING
Proper brake hose routing is essential to in-
sure safe vehicle operation.
ECA
NOTICE
Make sure that the pipe portion of the brake
hose touches the projection “a” on the
brake caliper.
Specified brake fluid
DOT 4
2
3
1
23
1
Brake hose union bolt 30 Nm (3.0 m·kgf, 22 ft·lbf)
12
New
New
1 3
4
2NewNew
New
T R..

REAR BRAKE
5-32
2. Pour brake fluid to the brake fluid reservoir up to the specified level.
EWA
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.
ECA
NOTICE
Brake fluid may damage painted surfaces
and plastic parts. Therefore, always clean
up any spilt brake fluid immediately.
3. Bleed:
• Brake systemRefer to “BLEEDING THE BRAKE SYS-
TEM” on page 3-25.
4. Check: • Brake fluid level
The minimum level mark “a” or below 
Add.
Refer to “CHECKING THE BRAKE FLUID
LEVEL” on page 3-30. 5. Check:
• Brake pedal operation
A softy or spongy feeling  Bleed the brake
system.
Refer to “BLEEDING THE BRAKE SYS-
TEM” on page 3-25.
Specified brake fluid
DOT 4
a
a