warning YAMAHA YZ450F 2003 Owner's Guide

5 - 21
CHASFRONT BRAKE AND REAR BRAKE
2. Install:
Brake lever 1
Bolt (brake lever) 2
Nut (brake lever) 3
NOTE:
Apply the lithium soap base grease on the
brake lever sliding surface, bolt and contacting
surface of the master cylinder piston.
Rear master cylinder
1. Install:
Copper washer 1
Brake hose 2
Union bolt 3
WARNING
Always use new copper washers.
ACHTUNG:CAUTION:
Install the brake hose so that its pipe por-
tion a directs as shown and lightly
touches the projection b on the master
cylinder.
T R..6 Nm (0.6 m · kg, 4.3 ft · lb)
T R..6 Nm (0.6 m · kg, 4.3 ft · lb)
New
T R..30 Nm (3.0 m · kg, 22 ft · lb)
2. Install:
Master cylinder 1
Bolt (master cylinder) 2
3. Install:
Spring 1
Brake pedal 2
O-ring 3
Bolt (brake pedal) 4
Clip 5
NOTE:
Apply the lithium soap base grease on the
bolt, O-ring and brake pedal bracket.
Install the clip with its stopper portion a fac-
ing inward.
T R..11 Nm (1.1 m · kg, 8.0 ft · lb)
New
T R..26 Nm (2.6 m · kg, 19 ft · lb)

5 - 23
CHASFRONT BRAKE AND REAR BRAKE
4. Install:
Copper washer 1
Brake hose 2
Union bolt 3
WARNING
Always use new copper washers.
ACHTUNG:CAUTION:
Install the brake hose so that its pipe por-
tion a directs as shown and lightly
touches the projection b on the master
cylinder.
New
T R..30 Nm (3.0 m · kg, 22 ft · lb)
Rear brake hose
1. Install:
Copper washer 1
Brake hose 2
Union bolt 3
WARNING
Always use new copper washers.
ACHTUNG:CAUTION:
Install the brake hose so that its pipe por-
tion a directs as shown and lightly
touches the projection b on the caliper.
New
T R..30 Nm (3.0 m · kg, 22 ft · lb)

5 - 24
CHASFRONT BRAKE AND REAR BRAKE
2. Install:
Brake hose holder 1
Screw (brake hose holder) 2
ACHTUNG:CAUTION:
After installing the brake hose holders,
make sure the brake hose does not contact
the spring (rear shock absorber). If it does,
correct its twist.
T R..1 Nm (0.1 m · kg, 0.7 ft · lb)
Brake fluid
1. Fill:
Brake fluid
Until the fluid level reaches “LOWER”
level line a.
WARNING
Use only the designated quality brake
fluid:
otherwise, the rubber seals may deterio-
rate, causing leakage and poor brake per-
formance.
Refill with the same type of brake fluid;
mixing fluids may result in a harmful chem-
ical reaction and lead to poor performance.
Be careful that water does not enter the
master cylinder when refilling. Water will
significantly lower the boiling point of the
fluid and may result in vapor lock.
ACHTUNG:CAUTION:
Brake fluid may erode painted surfaces or
plastic parts. Always clean up spilled fluid
immediately.
ÅFront
ıRear
Recommended brake fluid:
DOT #4
Å
ı

5 - 26
CHASFRONT FORK
EC550000
FRONT FORK
Extent of removal:1 Front fork removal
Extent of removal Order Part name Q’ty Remarks
Preparation for removalFRONT FORK REMOVAL
Hold the machine by placing the
suitable stand under the engine.
WARNING
Support the machine securely so there is nodanger of it falling over.
Front wheel Refer to “FRONT WHEEL AND REAR
WHEEL” section.
Front caliper Refer to “FRONT BRAKE AND REAR
BRAKE” section.
Number plate
Handlebar Refer to “HANDLEBAR” section.
1 Protector 1
2 Brake hose holder 2
3 Pinch bolt (handle crown) 2 Only loosening.
4 Cap bolt 1Loosen when disassembling the front fork.
5 Pinch bolt (under bracket) 2 Only loosening.
6 Front fork 1
1

5 - 30
CHAS
EC554200
Base valve
1. Inspect:
Valve assembly 1
Wear/damage → Replace.
O-ring 2
Damage → Replace.
EC554400
Fork spring
1. Measure:
Fork spring free length a
Out of specification → Replace.
EC554502
Inner tube
1. Inspect:
Inner tube surface a
Score marks → Repair or replace.
Use #1,000 grit wet sandpaper.
Damaged oil lock piece → Replace.
Inner tube bends
Out of specification → Replace.
Use the dial gauge 1.
NOTE:
The bending value is shown by one half of the
dial gauge reading.
WARNING
Do not attempt to straighten a bent inner
tube as this may dangerously weaken the
tube.
EC554600
Outer tube
1. Inspect:
Outer tube 1
Score marks/wear/damage → Replace.
Fork spring free length:
Standard Limit
460 mm (18.1 in) 455 mm (17.9 in)
Inner tube bending limit:
0.2 mm (0.008 in)
FRONT FORK

5 - 35
CHASFRONT FORK
19. Wait ten minutes until the air bubbles
have been removed from the front fork,
and the oil has dispense evenly in system
before setting recommended oil level.
NOTE:
Fill with the fork oil up to the top end of the
outer tube, or the fork oil will not spread over to
every part of the front forks, thus making it
impossible to obtain the correct level.
Be sure to fill with the fork oil up to the top of
the outer tube and bleed the front forks.
20. Measure:
Oil level (left and right) a
Out of specification → Adjust.
NOTE:
Be sure to install the spring guide 2 when
checking the oil level.
WARNING
Never fail to make the oil level adjustment
between the maximum and minimum level
and always adjust each front fork to the
same setting. Uneven adjustment can
cause poor handling and loss of stability.
Standard oil level:
135 mm (5.31 in)
Extent of adjustment:
80 ~ 150 mm (3.15 ~ 5.91 in)
From top of outer tube with
inner tube and damper rod 1
fully compressed without
spring.

5 - 40
CHAS
EC5B3000
REMOVAL POINTS
EC5B3100
Master cylinder
1. Remove:
Master cylinder bracket 1
Master cylinder 2
ACHTUNG:CAUTION:
Do not let the master cylinder hang on the
brake hose.
Keep the master cylinder cap side hori-
zontal to prevent air from coming in.
EC5B3200
Grip
1. Remove:
Grip 1
NOTE:
Blow in air between the handlebar or tube
guide and the grip. Then remove the grip
which has become loose.
EC5B4000
INSPECTION
EC5B4100
Handlebar
1. Inspect:
Handlebar 1
Bends/cracks/damage → Replace.
WARNING
Do not attempt to straighten a bent handle-
bar as this may dangerously weaken the
handlebar.
HANDLEBAR

5 - 42
CHASHANDLEBAR
4. Install:
Collar 1
Cover (grip cap) 2
Throttle grip 3
NOTE:
Apply the lithium soap base grease on the
throttle grip sliding surface.
5. Install:
Throttle cables 1
To tube guide 2.
NOTE:
Apply the lithium soap base grease on the
throttle cable end and tube guide cable wind-
ing portion.
6. Install:
Throttle cable cap 1
Screw (throttle cable cap) 2
WARNING
After tightening the screws, check that the
throttle grip 3 moves smoothly. If it does
not, retighten the bolts for adjustment.
T R..4 Nm (0.4 m · kg, 2.9 ft · lb)
7. Install:
Cover (grip cap) 1
Cover (throttle cable cap) 2

5 - 45
CHAS
EC560000
STEERING
Extent of removal:1 Under bracket removal2 Bearing removal
Extent of removal Order Part name Q’ty Remarks
STEERING REMOVAL
WARNING
Support the machine securely so there is nodanger of it falling over.
Refer to “HANDLEBAR” section. Preparation for removal Hold the machine by placing the
suitable stand under the engine.
Number plate
Handlebar
Cable guide
Front fender
1 Steering shaft nut 1
2 Front fork 2 Refer to “FRONT FORK” section.
3 Handle crown 1
4 Ring nut 1 Use special tool.
Refer to “REMOVAL POINTS”.
5 Under bracket 1
6 Ball race cover 1
7 Bearing (upper) 1
8 Bearing (lower) 1 Refer to “REMOVAL POINTS”.
9Ball race
2Refer to “REMOVAL POINTS”.
2
1
STEERING

5 - 46
CHAS
EC563000
REMOVAL POINTS
EC563202
Ring nut
1. Remove:
Ring nut 1
Use the ring nut wrench 2.
WARNING
Support the steering shaft so that it may
not fall down.
Ring nut wrench:
YU-33975/90890-01403
EC563300
Bearing (lower)
1. Remove:
Bearing (lower) 1
Use the floor chisel 2.
ACHTUNG:CAUTION:
Take care not to damage the steering shaft
thread.
EC563400
Ball race
1. Remove:
Ball race 1
Remove the ball race using long rod 2
and the hammer.
EC564000
INSPECTION
EC564200
Steering shaft
1. Inspect:
Steering shaft 1
Bend/damage → Replace.
STEERING