Yamaha YZ450F(B) 2012 Owner's Service Manual page 92

4. Measure:
• Camshaft-to-cap clearance
Out of specification → Measure
camshaft outside diameter.
Camshaft-to-cap clear-
ance:
0.028–0.062 mm
(0.0011–0.0024 in)
<Limit>:0.08 mm (0.003
in)
Measurement steps:
a. Install the camshaft onto the cylin-
der head.
b. Position a strip of Plastigauge
"1" onto the camshaft.
c. Install the clip, dowel pins and
camshaft caps.
Bolt (camshaft cap):
10 Nm (1.0 m•kg, 7.2
ft•lb)
• Tighten the bolts (camshaft cap) in
a crisscross pattern from innermost
to outer caps.
• Do not turn the camshaft when
measuring clearance with the
®
Plastigauge .
d. Remove the camshaft caps and
measure the width of the Plasti-
®
gauge "1".
5. Measure:
• Camshaft outside diameter "a"
Out of specification → Replace
the camshaft.
Within specification → Replace
camshaft case and camshaft
caps as a set.
Camshaft outside diame-
ter:
21.959–21.972 mm
(0.8645–0.8650 in)
CHECKING THE CAMSHAFT
SPROCKET
1. Inspect:
• Camshaft sprocket "1"
Wear/damage → Replace the
camshaft assembly and timing
chain as a set.
®
CHECKING THE
DECOMPRESSION SYSTEM
1. Check:
• Decompression system
Checking steps:
a. Check that the decompression
mechanism cam "1" moves
smoothly.
b. Check that the decompression
mechanism cam lever pin "2" proj-
ects from the camshaft.
CHECKING THE TIMING CHAIN
TENSIONER
1. Check:
• While pressing the tensioner rod
lightly with fingers, use a thin
screwdriver "1" and wind the ten-
sioner rod up fully clockwise.
• When releasing the screwdriver
by pressing lightly with fingers,
make sure that the tensioner rod
will come out smoothly.
• If not, replace the tensioner as-
sembly.
4-11
CAMSHAFTS
INSTALLING THE CAMSHAFT
1. Install:
• Exhaust camshaft "1"
• Intake camshaft "2"
Installation steps:
a. Turn the crankshaft counterclock-
wise with a wrench.
• Apply the molybdenum disulfide oil
on the camshafts.
• Apply the engine oil on the decom-
pression system.
• Fill the cylinder head with engine oil
up to the tops "a" of the valve lifters.
b. Align the alignment mark "a" on
the rotor with the alignment mark
"b" on the crankcase cover.
The alignment mark "a" on the ro-
tor is there for camshaft installa-
tion. This alignment mark is
stamped 23° ATDC.