2008 YAMAHA YZ450F wheel size

2-3
MAINTENANCE SPECIFICATIONS
MAINTENANCE SPECIFICATIONS
ENGINEWheel travel:
Front wheel travel 300 mm (11.8 in)
Rear wheel travel 313 mm (12.3 in)
Electrical:
Ignition system CDI magneto
Item Standard Limit
Cylinder head:
Warp limit ---- 0.05 mm (0.002
in)
Cylinder:
Bore size 95.00–95.01 mm (3.7402–3.7406 in) ----
Out of round limit ---- 0.05 mm (0.002
in)
Camshaft:
Drive method Chain drive (Left) ----
Camshaft cap inside diameter 22.000–22.021 mm (0.8661–0.8670 in) ----
Camshaft outside diameter 21.959–21.972 mm (0.8645–0.8650 in) ----
Shaft-to-cap clearance 0.028–0.062 mm (0.0011–0.0024 in) 0.08 mm (0.003
in)
Cam dimensions
Intake "A" 31.200–31.300 mm (1.2283–1.2323 in) 31.100 mm
(1.2244 in)
Intake "B" 22.550–22.650 mm (0.8878–0.8917 in) 22.450 mm
(0.8839 in)
Exhaust "A" 30.900–31.000 mm (1.2165–1.2205 in) 30.800 mm
(1.2126 in)
Exhaust "B" 22.468–22.568 mm (0.8846–0.8885 in) 22.368 mm
(0.8806 in)
Camshaft runout limit ---- 0.03 mm
(0.0012 in)

2-9
MAINTENANCE SPECIFICATIONS
Optional spring Yes←----
Enclosed gas pressure 1,000 kPa (10 kg/cm
2,
142 psi)←----
Swingarm:
Swingarm free play limit
End ---- 1.0 mm (0.04
in)
Wheel:
Front wheel type Spoke wheel ----
Rear wheel typeSpoke wheel ----
Front rim size/material 21 × 1.60/Aluminum ----
Rear rim size/material 19 × 2.15/Aluminum ----
Rim runout limit:
Radial ---- 2.0 mm (0.08
in)
Lateral ---- 2.0 mm (0.08
in)
Drive chain:
Type/manufacturer DID520DMA2 SDH/DAIDO ----
Number of links 113 links + joint ----
Chain slack 48–58 mm (1.9–2.3 in) ----
Chain length (15 links) ---- 242.9 mm
(9.563 in)
Front disc brake:
Disc outside dia.×Thickness 250 × 3.0 mm (9.84 × 0.12 in) 250 × 2.5 mm
(9.84 × 0.10 in)
Pad thickness 4.4 mm (0.17 in) 1.0 mm (0.04
in)
Master cylinder inside dia. 9.52 mm (0.375 in) ----
Caliper cylinder inside dia. 22.65 mm (0.892 in) × 2 ----
Brake fluid type DOT #4 ----
Rear disc brake:
Disc outside dia.×Thickness 245 × 4.0 mm (9.65 × 0.16 in) 245 × 3.5 mm
(9.65 × 0.14 in)
Deflection limit ---- 0.15 mm
(0.006 in)
Pad thickness 6.4 mm (0.25 in) 1.0 mm (0.04
in)
Master cylinder inside dia. 11.0 mm (0.433 in) ----
Caliper cylinder inside dia. 25.4 mm (1.000 in) × 1 ----
Brake fluid type DOT #4 ----
Brake lever and brake pedal:
Brake lever position 95 mm (3.74 in) ----
Brake pedal height (vertical height above footrest
top)5 mm (0.20 in) ----
Clutch lever free play (lever end) 8–13 mm (0.31–0.51 in) ----
Throttle grip free play3–5 mm (0.12–0.20 in) ---- Item Standard Limit

2-11
TIGHTENING TORQUES
Throttle cable (return) M12 × 1.0 1 11 1.1 8.0
Throttle cable cover M5 × 0.8 2 4 0.4 2.9
Hot starter plunger M12 × 1.0 1 2 0.2 1.4
Hot starter cable adjust bolt and locknut M6 × 0.75 1 4 0.4 2.9
Air filter element M6 × 1.0 1 2 0.2 1.4
Radiator stay M6 × 1.0 6 7 0.7 5.1
Radiator M6 × 1.0 4 10 1.0 7.2
Radiator hose clamp M6 × 1.0 8 2 0.2 1.4
Radiator pipe 1, 2 M6 × 1.0 2 10 1.0 7.2
Impeller M8 × 1.25 1 14 1.4 10
Water pump housing cover M6 × 1.0 3 10 1.0 7.2
Coolant drain bolt M6 × 1.0 1 10 1.0 7.2
Oil pump cover M4 × 0.7 1 2 0.2 1.4
Oil pump M6 × 1.0 2 10 1.0 7.2
Oil pump drive gear shaft M6 × 1.0 1 10 1.0 7.2
Oil filter element drain bolt M6 × 1.0 1 10 1.0 7.2
Oil filter element cover M6 × 1.0 2 10 1.0 7.2
Oil pressure check bolt M6 × 1.0 1 10 1.0 7.2
△Oil hose clamp — 2 2 0.2 1.4
Crankshaft end accessing screw M27 × 1.5 1 10 1.0 7.2
Timing mark accessing screw M14 × 1.5 1 6 0.6 4.3
Clutch cover M6 × 1.0 7 10 1.0 7.2
Right crankcase cover M6 × 1.0 8 10 1.0 7.2
Right crankcase cover M6 × 1.0 2 12 1.2 8.7
Left crankcase cover M6 × 1.0 8 10 1.0 7.2
Crankcase M6 × 1.0 12 12 1.2 8.7
Clutch cable holder M6 × 1.0 2 10 1.0 7.2
Oil drain bolt (right crankcase) M10 × 1.25 1 20 2.0 14
Oil drain bolt (left crankcase) M8 × 1.25 1 20 2.0 14
Oil check bolt (crankcase) M6 × 1.0 1 10 1.0 7.2
Oil strainer M6 × 1.0 1 10 1.0 7.2
Crankcase bearing stopper M6 × 1.0 8 10 1.0 7.2
Crankcase bearing stopper (crankshaft) M6 × 1.0 4 14 1.4 10
Drive axle oil seal stopper M6 × 1.0 2 10 1.0 7.2
Kick shaft ratchet wheel guide M6 × 1.0 2 12 1.2 8.7
Kickstarter crank M8 × 1.25 1 33 3.3 24
Screw (kickstarter crank) M6 × 1.0 1 7 0.7 5.1
Primary drive gear M20 × 1.0 1 110 11.0 80
Clutch boss M20 × 1.0 1 75 7.5 54
Clutch cable adjust bolt and locknut M6 × 0.75 1 4 0.4 2.9
Clutch spring M6 × 1.0 6 10 1.0 7.2
Balancer M10 × 1.0 1 45 4.5 32
Balancer shaft driven gear M14 × 1.0 1 50 5.0 36
Balancer weight M6 × 1.0 3 10 1.0 7.2Part to be tightened Thread size Q'tyTightening torque
Nm m•kg ft•lb

2-13
TIGHTENING TORQUES
△Front wheel axle and axle nut M16 × 1.5 1 105 10.5 75
△Front wheel axle holder M8 × 1.25 4 21 2.1 15
△Front brake disc and wheel hub M6 × 1.0 6 12 1.2 8.7
△Rear brake disc and wheel hub M6 × 1.0 6 14 1.4 10
△Footrest bracket and frame M10 × 1.25 4 55 5.5 40
△Brake pedal mounting M8 × 1.25 1 26 2.6 19
△Rear brake master cylinder and frame M6 × 1.0 2 10 1.0 7.2
Rear brake master cylinder cap M4 × 0.7 2 2 0.2 1.4
△Rear brake hose union bolt (brake caliper) M10 × 1.25 1 30 3.0 22
△Rear brake hose union bolt (brake master cylinder) M10 × 1.25 1 30 3.0 22
△Rear wheel axle and axle nut M20 × 1.5 1 125 12.5 90
△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 19 1.9 13
Engine mounting:
△Upper engine bracket and frame M10 × 1.25 4 55 5.5 40
△Lower 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 1 55 5.5 40
△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
CDI unit bracket M6 × 1.0 2 7 0.7 5.1
Cable guide and CDI unit bracket M5 × 0.8 2 4 0.4 2.9
Cable guide and frame M5 × 0.8 1 5 0.5 3.6
△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 frame and frame (upper) M8 × 1.25 1 38 3.8 27
△Rear frame and frame (lower) M8 × 1.25 2 32 3.2 23
△Swingarm and brake hose holder M5 × 0.8 4 2 0.2 1.4
Swingarm and patch M4 × 0.7 4 2 0.2 1.4
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 4 6 0.6 4.3
△Fuel tank mounting boss and frame M10 × 1.25 1 20 2.0 14
△Fuel tank mounting M6 × 1.0 2 9 0.9 6.5
△Fuel tank and fuel cock M6 × 1.0 2 4 0.4 2.9Part to be tightened Thread size Q'tyTightening torque
Nm m•kg ft•lb

7-6
CHASSIS
CHASSIS
SELECTION OF THE SECONDARY
REDUCTION RATIO (SPROCKET)
ondary gear reduction ratio>
• It is generally said that the second-
ary gear ratio should be reduced for
a longer straight portion of a speed
course and should be increased for
a course with many corners. Actual-
ly, however, as the speed depends
on the ground condition of the day
of the race, be sure to run through
the circuit to set the machine suit-
able for the entire course.
• In actuality, it is very difficult to
achieve settings suitable for the en-
tire course and some settings may
be sacrificed. Thus, the settings
should be matched to the portion of
the course that has the greatest ef-
fect on the race result. In such a
case, run through the entire course
while making notes of lap times to
find the best balance; then, deter-
mine the secondary reduction ratio.
• If a course has a long straight por-
tion where a machine can run at
maximum speed, the machine is
generally set such that it can devel-
op its maximum revolutions toward
the end of the straight line, with care
taken to avoid the engine over-rev-
ving.
Riding technique varies from rider to
rider and the performance of a ma-
chine also vary from machine to ma-
chine. Therefore, do not imitate other
rider's settings from the beginning but
choose your own setting according to
the level of your riding technique.
DRIVE AND REAR WHEEL
SPROCKETS SETTING PARTS
TIRE PRESSURE
Tire pressure should be adjust to suit
the road surface condition of the cir-
cuit.
• Under a rainy, muddy, sandy, or
slippery condition, the tire pressure
should be lower for a larger area of
contact with the road surface.
• Under a stony or hard road condi-
tion, the tire pressure should be
higher to prevent a flat tire.
FRONT FORK SETTING
The front fork setting should be made
depending on the rider's feeling of an
actual run and the circuit conditions.The front fork setting includes the fol-
lowing three factors:
1. Setting of air spring characteris-
tics
• Change the fork oil amount.
2. Setting of spring preload
• Change the spring.
3. Setting of damping force
• Change the compression damp-
ing.
• Change the rebound damping.
The spring acts on the load and
the damping force acts on the
cushion travel speed.
CHANGE IN AMOUNT AND
CHARACTERISTICS OF FORK OIL
Damping characteristic near the final
stroke can be changed by changing
the fork oil amount.
Adjust the oil amount in 5 cm3 (0.2
Imp oz, 0.2 US oz) increments or
decrements. Too small oil amount
causes the front fork to produce a
noise at full rebound or the rider to
feel some pressure on his hands
or body. Alternatively, too large oil
amount will cause the air spring
characteristics to have a tendency
to be stiffer with the consequent
deteriorated performance and
characteristics. Therefore, adjust
the front fork within the specified
range.
A. Air spring characteristics in
relation to oil amount change
B. Load Secondary reduction ratio =
Number of rear wheel sprocket
teeth/Number of drive sprocket
teeth
Standard secondary
reduction ratio49/13
(3.769)
Part name Size Part number
Drive
sprocket "1"
(STD) 13T 9383B-13233
Rear wheel
sprocket "2"
47T 1C3-25447-00
48T 1C3-25448-00
(STD) 49T 1C3-25449-00
50T 1C3-25450-00
51T 1C3-25451-00
52T 1C3-25452-00
Standard tire pressure:
100 kPa (1.0 kgf/cm
2,
15 psi)
Extent of adjustment:
60–80 kPa (0.6–0.8 kgf/
cm
2, 9.0–12 psi)
Extent of adjustment:
100–120 kPa (1.0–1.2
kgf/cm
2, 15–18 psi)
Standard oil amount:
350 cm3 (12.3 Imp oz,
11.8 US oz)
Extent of adjustment:
300–375 cm
3(10.6–13.2
Imp oz, 10.1–12.7 US
oz)