Yamaha YZ450F(Y Owner's Manual page 86

REMOVING THE CAMSHAFT
1. Remove:
• Timing mark accessing screw "1"
• Crankshaft end accessing screw
"2"
2. Align:
• T.D.C. mark
With align mark.
Checking steps:
a. Turn the crankshaft counterclock-
wise with a wrench.
b. Align the T.D.C. mark "a" on the
rotor with the align mark "b" on the
crankcase cover when piston is at
T.D.C. on compression stroke.
In order to be sure that the piston is at
Top Dead Center, the punch mark "c"
on the exhaust camshaft and the
punch mark "d" on the intake cam-
shaft must align with the cylinder
head surface, as shown in the illustra-
tion.
3. Remove:
• Timing chain tensioner cap bolt
"1"
• Timing chain tensioner "2"
• Gasket
4. Remove:
• Bolt (camshaft cap) "1"
• Camshaft cap "2"
• Clip
Remove the bolts (camshaft cap) in a
crisscross pattern, working from the
outside in.
The bolts (camshaft cap) must be
removed evenly to prevent dam-
age to the cylinder head, cam-
shafts or camshaft caps.
5. Remove:
• Exhaust camshaft "1"
• Intake camshaft "2"
Attach a wire "3" to the timing chain to
prevent it from falling into the crank-
case.
CHECKING THE CAMSHAFT
1. Inspect:
• Cam lobe
Pitting/scratches/blue discolora-
tion → Replace.
2. Measure:
• Cam lobe length "a" and "b"
Out of specification → Replace.
4-16
CAMSHAFTS
Cam lobes length:
Intake "a":
31.200–31.300 mm
(1.2283–1.2323 in)
<Limit>:
31.100 mm (1.2244 in)
Intake "b":
22.550–22.650 mm
(0.8878–0.8917 in)
<Limit>:
22.450 mm (0.8839 in)
Exhaust "a":
30.900–31.000 mm
(1.2165–1.2205 in)
<Limit>:
30.800 mm (1.2126 in)
Exhaust "b":
22.468–22.568 mm
(0.8846–0.8885 in)
<Limit>:
22.368 mm (0.8806 in)
3. Measure:
• Runout (camshaft)
Out of specification → Replace.
Runout (camshaft):
Less than 0.03 mm
(0.0012 in)
4. Measure:
• Camshaft-to-cap clearance
Out of specification → Measure
camshaft outside diameter.