Yamaha WR450FB 2012 Owner's Service Manual page 219

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5. Measure:
• Camshaft journal diameter "a"
Out of specification
- >
Replace the cam-
shaft.
With in specification
-t
Replace the cylinder
head and the camshaft caps as a set.
EAS23870
Camshaft journal diameter
21.959-21.972 mm (0.8645-
0.8650 in)
CHECKING THE TIMING CHAIN AND CAM-
SHAFT SPROCKET
1. Check:
• Timing chain "1"
Damage/stiffness
-t
Replace the timing
chain and camshaft and camshaft sprocket
as a set.
2. Check:
• Camshaft sprocket
More than 1/4 tooth wear "a"
-t
Replace th e
camshaft sprocket and the timing chain as a
set.
6-11
CAMSHAFT
1
a. 1/4 tooth
b. Correct
1. Timing chain roller
2. Camshaft sprocket
EAS23960
CHECKING THE TIMING CHAIN TENSION-
ERS
The following procedure applies to both of the
timing chain tensioners.
1. Check:
• Timing chain tensioner
Cracks/damage
-t
Replace.
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a. While pressing the tensioner rod lightly with
fingers, use a thin screwdriver "1" and wind
the tensioner rod up fully clockwise.
b. When releasing the screwdriver by pressing
lightly with fingers , make sure that the ten-
sioner rod will come out smoothly.
c. If not, replace the tensioner assembly.