brake YAMAHA YZ450F 2015 Repair Manual

HANDLEBAR
4-36
10.Install:
• Rubber cover “1”
• Cover (throttle cable housings) “2”
11.Install:
• Front brake master cylinder assembly “1”
• Front brake master cylinder holder “2”
• Bolt (brake master cylinder holder) “3”
TIP
• Install the brake master cylinder holder with
the “UP” mark facing up.
• Install in order for the top of the front brake
master cylinder assembly to be level.
• First, tighten the upper bolt, then the lower
bolt.12.Install:
• Clutch cable “1”
TIP
Before installation, apply the lithium-soap-
based grease to the clutch cable end.
13.Adjust:
• Clutch lever free play
Refer to “ADJUSTING THE CLUTCH LE-
VER FREE PLAY” on page 3-10.
14.Adjust:
• Throttle grip free play
Refer to “ADJUSTING THE THROTTLE
GRIP FREE PLAY” on page 3-11.
Front brake master cylinder hold-
er bolt
9 Nm (0.9 m·kgf, 6.5 ft·lbf)
T R..
Clutch lever free play
7.0–12.0 mm (0.28–0.47 in)
Throttle grip free play
3.0–5.0 mm (0.12–0.20 in)
1LS

FRONT FORK
4-37
EAS1SL5166
FRONT FORK
Removing the front fork legs
Order Part name Q’ty Remarks
Use a suitable stand to raise the front wheel
off the ground.
Front wheel Refer to “FRONT WHEEL” on page 4-3.
Front brake caliper Refer to “FRONT BRAKE” on page 4-11.
Number plate Refer to “GENERAL CHASSIS” on page 4-1.
1 Protector 1
2 Upper bracket pinch bolts 2 Loosen.
3 Damper assembly 1 Loosen.
4 Lower bracket pinch bolts 2 Loosen.
5 Front fork leg 1
For installation, reverse the removal proce-
dure.
3
2
4
5
1
T.R.21 Nm (2.1 mlbf) kgf, 15 ft
T.R.9 Nm (0.9 mlbf) kgf, 6.5 ft
T.R.5 Nm (0.5 mlbf) kgf, 3.6 ftT.R.5 Nm (0.5 mlbf) kgf, 3.6 ft

SWINGARM
4-60
EAS1SL5185
SWINGARM
Removing the swingarm
Order Part name Q’ty Remarks
Use a suitable stand to raise the front wheel
off the ground.
Brake hose holder Refer to “REAR BRAKE” on page 4-21.
Rear brake caliper Refer to “REAR BRAKE” on page 4-21.
Bolt (brake pedal)
Drive chain
1Collars 2
2Oil seals 2
3Thrust bearing 2
4Bushing 2
5Oil seals 2
6 Bearing 4
For installation, reverse the removal proce-
dure.
1
2
3
6
4
6
4
1
3
6
2
5
T.R.70 Nm (7.0 mlbf) kgf, 51 ft
T.R.4.0 Nm (0.40 mlbf) kgf, 2.9 ft

5
ENGINE
ENGINE REMOVAL......................................................................................... 5-1
REMOVING THE SILENCER ..................................................................... 5-6
REMOVING THE EXHAUST PIPE 2.......................................................... 5-6
REMOVING THE DRIVE SPROCKET ....................................................... 5-6
REMOVING THE ENGINE ......................................................................... 5-7
CHECKING THE SILENCER AND EXHAUST PIPE.................................. 5-7
CHANGING THE SILENCER FIBER ......................................................... 5-7
INSTALLING THE ENGINE........................................................................ 5-8
INSTALLING THE BRAKE PEDAL ............................................................ 5-9
INSTALLING THE DRIVE SPROCKET...................................................... 5-9
INSTALLING THE EXHAUST PIPE AND MUFFLER............................... 5-10
CAMSHAFT.................................................................................................... 5-11
REMOVING THE CAMSHAFT ................................................................. 5-13
CHECKING THE CAMSHAFT.................................................................. 5-14
CHECKING THE TIMING CHAIN AND CAMSHAFT SPROCKET .......... 5-15
CHECKING THE TIMING CHAIN TENSIONERS .................................... 5-15
CHECKING THE DECOMPRESSION SYSTEM...................................... 5-16
INSTALLING THE CAMSHAFTS ............................................................. 5-16
CYLINDER HEAD........................................................................................... 5-19
REMOVING THE CYLINDER HEAD........................................................ 5-21
CHECKING THE TIMING CHAIN GUIDE (INTAKE SIDE) ...................... 5-21
CHECKING THE CYLINDER HEAD ........................................................ 5-21
INSTALLING THE CYLINDER HEAD ...................................................... 5-22
VALVES AND VALVE SPRINGS................................................................... 5-24
REMOVING THE VALVES ....................................................................... 5-25
CHECKING THE VALVES AND VALVE GUIDES ................................... 5-26
CHECKING THE VALVE SEATS ............................................................. 5-27
CHECKING THE VALVE SPRINGS......................................................... 5-29
CHECKING THE VALVE LIFTERS .......................................................... 5-29
INSTALLING THE VALVES ..................................................................... 5-30
CYLINDER AND PISTON............................................................................... 5-32
REMOVING THE PISTON ....................................................................... 5-33
CHECKING THE CYLINDER AND PISTON ............................................ 5-33
CHECKING THE PISTON RINGS............................................................ 5-34
CHECKING THE PISTON PIN ................................................................. 5-35
INSTALLING THE PISTON AND CYLINDER .......................................... 5-35

ENGINE REMOVAL
5-4
Removing the engine
Order Part name Q’ty Remarks
Use a suitable stand to raise the front wheel
off the ground.
Seat Refer to “GENERAL CHASSIS” on page 4-1.
Side cover (left/right) Refer to “GENERAL CHASSIS” on page 4-1.
Air scoop (left / right) Refer to “GENERAL CHASSIS” on page 4-1.
Rear fender Refer to “GENERAL CHASSIS” on page 4-1.
Fuel tank Refer to “FUEL TANK” on page 7-1.
Exhaust pipe and silencer Refer to “ENGINE REMOVAL” on page 5-1.
Air filter case Refer to “THROTTLE BODY” on page 7-5.
Throttle body Refer to “THROTTLE BODY” on page 7-5.
Clutch cable Refer to “CLUTCH” on page 5-37.
Shift pedal Refer to “SHIFT SHAFT” on page 5-49.
1 Engine guard 1
2 Brake pedal 1
3Spring 1
4 Cylinder head breather hose 1
5 Drive sprocket cover 1
6 Drive chain guide 1
New
New
LS
M
8
8
7
6
11
45
New
1 10
3
2

ENGINE REMOVAL
5-6
EAS1SL5198REMOVING THE SILENCER
1. Remove:
• Rear shock absorber assembly lower bolt
“1”
• Connecting arm bolt (frame side) “2”
• Silencer “3”
TIP
Move the rear shock absorber to the left side of
the chassis, and remove the silencer.
EAS1SL5199REMOVING THE EXHAUST PIPE 2
1. Remove:
• Exhaust pipe 2
TIP
Put the Exhaust pipe 2 into the state as shown
by moving this, and then remove it.
EAS1SL5200REMOVING THE DRIVE SPROCKET
1. Straighten the lock washer tab.
2. Remove:
• Nut (drive sprocket) “1”
• Lock washer “2”
TIP
Loosen the nut while applying the rear brake.
3. Remove:
• Drive sprocket “1”
• Drive chain “2”
TIP
Remove the drive sprocket together with the
drive chain.
1 2
3

ENGINE REMOVAL
5-9
EAS1SL5205INSTALLING THE BRAKE PEDAL
1. Install:
• Spring “1”
• Brake pedal “2”
• O-rings “3”
• Bolt (brake pedal) “4”
•Clip “5”
TIP
Apply the lithium soap base grease on the bolt,
O-rings and brake pedal bracket.
EAS1SL5206INSTALLING THE DRIVE SPROCKET
1. Install:
• Drive sprocket “1”
• Drive chain “2”
TIP
Install the drive sprocket together with the drive
chain.2. Install:
• Lock washer “1”
• Nut (drive sprocket) “2”
TIP
Tighten the nut while applying the rear brake.
ECA33DD040
NOTICE
Make sure to tighten to specification; other-
wise, it may damage the other part that is
fastened together.
3. Bend the lock washer tab to lock the nut.
4. Install:
• Drive sprocket guide
• Drive sprocket cover “1”
• Bolt (drive sprocket cover) “2” Bolt (brake pedal)
26 Nm (2.6 m·kgf, 19 ft·lbf)
M
78
9
9 8
7
4 1
2
43
5
56
New
T R..
1 2
3
45
LS
Nut (drive sprocket)
75 Nm (7.5 m·kgf, 54 ft·lbf)
Bolt (drive sprocket cover)
7 Nm (0.7 m·kgf, 5.1 ft·lbf)
New
T R..
T R..
21

CLUTCH
5-37
EAS1SL5233
CLUTCH
Removing the clutch
Order Part name Q’ty Remarks
Engine oilDrain.
Refer to “CHANGING THE ENGINE OIL” on
page 3-15.
Brake pedal Refer to “ENGINE REMOVAL” on page 5-1.
1 Clutch cable 1 Disconnect.
2 Clutch cover 1
3 O-ring 1
4 Clutch spring 6
5 Pressure plate 1
6 Push rod 1 1
7 Circlip 1
8Washers 1
9 Bearing 1
10 Ball 1
11 Push rod 2 1
12 Friction plate 1 5
13 Clutch plate 7
LS
New
New
New
2
3 45
78961011
13
12
12
18
1
14
13
13
17
16
15
T.R.
T.R.
T.R.
T.R.
LT

CLUTCH
5-39
Removing the right crankcase cover
Order Part name Q’ty Remarks
Right engine guard Refer to “ENGINE REMOVAL” on page 5-1.
Engine oilDrain.
Refer to “CHANGING THE ENGINE OIL” on
page 3-15.
CoolantDrain.
Refer to “CHANGING THE COOLANT” on
page 3-8.
Brake pedal Refer to “ENGINE REMOVAL” on page 5-1.
Clutch cover Refer to “CLUTCH” on page 5-37.
1 Oil filter element cover 1
2 Oil filter element 1
3 Radiator pipe 2 1
4 Kickstarter lever 1
5 Right crankcase cover 1
6 Gaskets 1
7 Dowel pin 2
8Collar 1
For installation, reverse the removal proce-
dure.
T.R.
LS
New
New
67
2
5
4
1
7 8
New
3
LS
New
New
LS
LS
NewNew
LT
LS

TROUBLESHOOTING
9-3
Fuel system
1. Throttle body
• Damaged or loose throttle body joint
2. Air filter
• Clogged air filter element
Chassis
1. Brake(s)
• Dragging brake
Electrical system
1. Spark plug
• Incorrect spark plug gap
• Incorrect spark plug heat range
2. Ignition system
• Faulty ECU
• Faulty coolant temperature sensor
EAS1SL5360OVERCOOLING
Cooling system
• Faulty coolant temperature sensor
EAS1SL5361POOR BRAKING PERFORMANCE
• Worn brake pad
• Worn brake disc
• Air in hydraulic brake system
• Leaking brake fluid
• Defective master cylinder kit
• Faulty brake caliper kit
• Faulty brake caliper seal
• Loose union bolt
• Damaged brake hose
• Oil or grease on the brake disc
• Oil or grease on the brake pad
• Incorrect brake fluid level
EAS1SL5362FAULTY FRONT FORK LEGS
Leaking oil
• Bent, damaged, or rusty inner tube
• Cracked or damaged outer tube
• Improperly installed oil seal
• Damaged oil seal lip
• Incorrect oil level (high)
• Loose damper rod assembly bolt
• Damaged damper rod assembly bolt copper
washer
• Cracked or damaged cap bolt O-ringMalfunction
• Bent or damaged inner tube
• Bent or damaged outer tube
• Broken fork spring
• Bent or damaged damper rod
• Incorrect oil viscosity
• Incorrect oil level
EAS1SL5363UNSTABLE HANDLING
1. Handlebar
• Bent or improperly installed handlebar
2. Steering head components
• Improperly installed upper bracket
• Improperly installed lower bracket
(improperly tightened ring nut)
• Bent steering stem
• Damaged ball bearing or bearing race
3. Front fork leg (s)
• Uneven oil levels (both front fork legs)
• Unevenly tensioned fork spring (both front
fork legs)
• Broken fork spring
• Bent or damaged inner tube
• Bent or damaged outer tube
4. Swingarm
• Worn bearing or bushing
• Bent or damaged swingarm
5. Rear shock absorber assembly (-ies)
• Faulty rear shock absorber spring
• Leaking oil or gas
6. Tire (s)
• Uneven tire pressures (front and rear)
• Incorrect tire pressure
• Uneven tire wear
7. Wheel (s)
• Incorrect wheel balance
• Broken or loose spoke
• Damaged wheel bearing
• Bent or loose wheel axle
• Excessive wheel runout
8. Frame
• Bent frame
• Damaged steering head pipe
• Improperly installed bearing race