length YAMAHA YZ450F 2006 User Guide

4 - 25
ENGCAMSHAFTS
6. Remove:
Clips
Exhaust camshaft 1
Intake camshaft 2
NOTE:
Attach a wire 3 to the timing chain to prevent
it from falling into the crankcase.
1
2
3
INSPECTION
Camshaft
1. Inspect:
Cam lobes
Pitting/scratches/blue discoloration →
Replace.
2. Measure:
Cam lobes length a and b
Out of specification → Replace.
Cam lobes length:
Intake:
a31.200 ~ 31.300 mm
(1.2283 ~ 1.2323 in)
: 31.100 mm
(1.2244 in)
b22.550 ~ 22.650 mm
(0.8878 ~ 0.8917 in)
: 22.450 mm
(0.8839 in)
Exhaust:
a30.950 ~ 31.050 mm
(1.2185 ~ 1.2224 in)
: 30.850 mm
(1.2146 in)
b22.494 ~ 22.594 mm
(0.8856 ~ 0.8895 in)
: 22.394 mm
(0.8817 in)
3. Measure:
Runout (camshaft)
Out of specification → Replace.
Runout (camshaft):
Less than 0.03 mm (0.0012 in)

4 - 40
ENGVALVES AND VALVE SPRINGS
Valve spring
1. Measure:
Valve spring free length a
Out of specification → Replace.
2. Measure:
Compressed spring force a
Out of specification → Replace.
bInstalled length
Free length (valve spring):
Intake:
37.03 mm (1.46 in)
: 36.03 mm (1.42 in)
Exhaust:
37.68 mm (1.48 in)
: 36.68 mm (1.44 in)
Compressed spring force:
Intake:
111.3 ~ 127.9 N at 27.87 mm
(11.3 ~ 13.0 kg at 27.87 mm,
24.91 ~ 28.66 lb at 1.10 in)
Exhaust:
127.4 ~ 146.4 N at 27.38 mm
(13.0 ~ 14.9 kg at 27.38 mm,
28.66 ~ 32.85 lb at 1.08 in)
3. Measure:
Spring tilt a
Out of specification → Replace.
Spring tilt limit:
Intake:
2.5°/1.61 mm (0.063 in)
Exhaust:
2.5°/1.65 mm (0.065 in)
Valve lifter
1. Inspect:
Valve lifter
Scratches/damage → Replace both lift-
ers and cylinder head.

4 - 51
ENGCLUTCH
EC493000
REMOVAL POINTS
EC483211
Clutch boss
1. Remove:
Nut 1
Lock washer 2
Clutch boss 3
NOTE:
Straighten the lock washer tab and use the
clutch holding tool 4 to hold the clutch boss.
ÈFor USA and CDN
ÉExcept for USA and CDN
Clutch holding tool:
YM-91042/90890-04086
È
É
EC494000
INSPECTION
EC484100
Clutch housing and boss
1. Inspect:
Clutch housing 1
Cracks/wear/damage → Replace.
Clutch boss 2
Scoring/wear/damage → Replace.
EC484201
Primary driven gear
1. Check:
Circumferential play
Free play exists → Replace.
Gear teeth
a
Wear/damage → Replace.
EC484400
Clutch spring
1. Measure:
Clutch spring free length
a
Out of specification → Replace springs
as a set.
Clutch spring free length:
Standard
47.8 mm (1.88 in) 46.8 mm (1.84 in)

5 - 31
CHAS
Base valve
1. Inspect:
Base valve 1
Wear/damage → Replace.
Contamination → Clean.
O-ring 2
Wear/damage → Replace.
Piston metal 3
Wear/damage → Replace.
Spring 4
Damage/fatigue → Replace base valve.
Air bleed screw 5
Wear/damage → Replace.
Collar
1. Inspect:
Piston metal 1
Wear/damage → Replace.
EC554400
Fork spring
1. Measure:
Fork spring free length a
Out of specification → Replace.
Fork spring free length:
Standard
454 mm (17.9 in) 449 mm (17.7 in)
FRONT FORK

5 - 67
CHASREAR SHOCK ABSORBER
2. Install:
•Spring seat 1
NOTE:
Install the spring seat with the projection a
brought into contact with the spring end, as
shown.
3. Tighten:
•Adjuster 1
4. Adjust:
•Spring length (installed)
Refer to “REAR SHOCK ABSORBER
SPRING PRELOAD ADJUSTMENT” sec-
tion in the CHAPTER 3.
5. Tighten:
•Locknut 1
Rear shock absorber
1. Install:
•Dust seal 1
•O-ring 2
•Collar 3
NOTE:
•Apply the molybdenum disulfide grease on
the dust seal lips and collars.
•Apply the lithium soap base grease on the O-
rings.
New

7 - 15
TUN
EC72P000
Front fork setting parts
•Front fork spring 1
* For EUROPE
NOTE:
The I.D. mark (slits) a is proved on the end of
the spring.TYPESPRING
RATESPRING
PART NUMBERI.D.
MARK
(slits)
SOFT0.398
0.408
0.418
0.428
0.438
0.4491C3-23141-A0
1C3-23141-B0
1C3-23141-C0
1C3-23141-D0
1C3-23141-E0
1C3-23141-F0I
II
III
IIII
IIIII
I-I
*STD 0.459 2S2-23141-M0–
STD 0.469 2S2-23141-L0–
STIFF 0.479 1C3-23141-J0 I-IIII
EC72B000
Rear suspension setting
The rear suspension setting should be made
depending on the rider’s feeling of an actual
run and the circuit conditions.
The rear suspension setting includes the fol-
lowing two factors:
1. Setting of spring preload
•Change the set length of the spring.
•Change the spring.
2. Setting of damping force
•Change the rebound damping.
•Change the compression damping.
SETTING

7 - 16
TUN
EC72C001
Choosing set length
1. Place a stand or block under the engine to
put the rear wheel above the floor, and
measure the length a between the rear
wheel axle center and the rear fender hold-
ing bolt.
2. Remove the stand or block from the engine
and with a rider astride the seat, measure
the sunken length b between the rear
wheel axle center and the rear fender hold-
ing bolt.
3. Loosen the locknut 1 and make adjust-
ment by turning the spring adjuster 2 to
achieve the standard figure from the sub-
traction of the length b from the length a.
NOTE:
•If the machine is new and after it is broken in,
the same set length of the spring may
change because of the initial fatigue, etc. of
the spring. Therefore, be sure to make re-
evaluation.
•If the standard figure cannot be achieved by
adjusting the spring adjuster and changing
the spring set length, replace the spring with
an optional one and make re-adjustment.
Standard figure:
90 ~ 100 mm (3.5 ~ 3.9 in)
SETTING

7 - 17
TUNSETTING
EC72G001
Setting of spring after replacement
After replacement, be sure to adjust the spring
to the set length [sunken length 90 ~ 100 mm
(3.5 ~ 3.9 in)] and set it.
1. Use of soft spring
•Set the soft spring for less rebound
damping to compensate for its less spring
load. Run with the rebound damping
adjuster one or two clicks on the softer
side and readjust it to suit your prefer-
ence.
2. Use of stiff spring
•Set the soft spring for more rebound
damping to compensate for its greater
spring load. Run with the rebound damp-
ing adjuster one or two clicks on the
stiffer side and readjust it to suit your
preference.
*Adjusting the rebound damping will be fol-
lowed more or less by a change in the com-
pression damping. For correction, turn the
low compression damping adjuster on the
softer side.
CAUTION:
When using a rear cushion other than cur-
rently installed, use the one whose overall
length
a does not exceed the standard as
it may result in faulty performance. Never
use one whose overall length is greater
than standard.
ÈCoverage of spring by weight
ÉRider weight
1Soft
2Standard
3Stiff
Length
a of standard shock:
488.5 mm (19.23 in)

7 - 18
TUNSETTING
EC72Q000
Rear shock absorber setting parts
•Rear shock spring 1
[Equal-pitch titanium spring]
[Equal-pitch steel spring]
[Unequal-pitch steel spring]
CAUTION:
Install the spring seat
2 to the titanium
spring.
NOTE:
•The unequal-pitch spring is softer in initial
characteristic than the equal-pitch spring and
is difficult to bottom out under full compres-
sion.
•The I.D. mark a is marked at the end of the
spring.
•Spring specification varies according to the
color and quantity of I.D. marks.
TYPESPRING
RATESPRING
PART NUMBERI.D.
MARKSPRING
FREE
LENGTH
(approx.)
SOFT4.5
4.7
4.9
5.1
5.31C3-22212-00
1C3-22212-10
1C3-22212-20
1C3-22212-30
1C3-22212-40Green
Red
Black
Blue
Yellow265
265
265
265
275
STD 5.5 1C3-22212-50 Pink 275
STIFF 5.7 1C3-22212-60 White 275
TYPESPRING
RATESPRING
PART NUMBERI.D.
MARK/
Q’TYSPRING
FREE
LENGTH
4.3 5UN-22212-00 Brown/1 260
TYPESPRING
RATE
(approx.)SPRING
PART NUMBERI.D.
MARK/
Q’TYSPRING
FREE
LENGTH
SOFT
STIFF4.5
4.7
4.9
5.1
5.3
5.5
5.75UN-22212-A0
5UN-22212-B0
5UN-22212-C0
5UN-22212-D0
5UN-22212-E0
5UN-22212-F0
5UN-22212-G0Green/2
Red/2
Black/2
Blue/2
Yellow/2
Pink/2
White/2275
275
275
275
275
275
275
a2 12

7 - 19
TUN
•Extent of adjustment (spring length)
[Titanium spring]
[Steel spring]SPRING FREE
LENGTHEXTENT OF
ADJUSTMENT b
Approx. 265 mm
(10.43 in)One I.D. mark
245.5 ~ 263.5 mm
(9.67 ~ 10.37 in)
Two I.D. marks
251.5 ~ 269.5 mm
(9.90 ~ 10.61 in)
Three I.D. marks
243.0 ~ 261.0 mm
(9.57 ~ 10.28 in)
Approx. 275 mm
(10.83 in)One I.D. mark
255.5 ~ 273.5 mm
(10.06 ~ 10.77 in)
Two I.D. marks
261.5 ~ 279.5 mm
(10.30 ~ 11.00 in)
Three I.D. marks
253.0 ~ 271.0 mm
(9.96 ~ 10.67 in)
SPRING FREE
LENGTHEXTENT OF
ADJUSTMENT b
260 mm (10.24 in)240.5 ~ 258.5 mm
(9.47 ~ 10.18 in)
275 mm (10.83 in)255.5 ~ 273.5 mm
(10.06 ~ 10.77 in)
SETTING