Yamaha YZ450F Owner's Service Manual page 93

REMOVING THE CAMSHAFT
1. Remove:
• Timing mark accessing screw "1"
• Crankshaft end accessing screw
"2"
2. Align:
• Alignment mark
Checking steps:
a. Turn the crankshaft counterclock-
wise with a wrench.
b. Align the alignment mark "a" on
the rotor with the alignment mark
"b" on the crankcase cover.
Make sure that the alignment mark
"c" on the exhaust camshaft sprocket
and the alignment mark "d" on the in-
take camshaft sprocket are aligned
with the edge of the cylinder head.
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 discolor-
ation → Replace.
2. Measure:
• Cam lobe length "a" and "b"
Out of specification → Replace.
4-12
CAMSHAFTS
Cam lobes length:
Intake "a":
37.750–37.850 mm
(1.4862–1.4902 in)
<Limit>:
37.650 mm (1.4823 in)
Intake "b":
28.129–28.229 mm
(1.1072–1.1114 in)
<Limit>:
28.029 mm (1.1035 in)
Exhaust "a":
33.540–33.640 mm
(1.3205–1.3244 in)
<Limit>:
33.440 mm (1.3165 in)
Exhaust "b":
24.769–24.869 mm
(0.9752–0.9791 in)
<Limit>:
24.669 mm (0.9712 in)
3. Measure:
• Runout (camshaft)
Out of specification → Replace.
Runout (camshaft):
Less than 0.03 mm
(0.0012 in)