Yamaha YZ 2018 Series Owner's Service Manual page 212

d. Remove the camshaft caps and then mea-
sure the width of the Plastigauge® "1".
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5. Measure:
• Camshaft journal diameter "a"
Out of specification  Replace the cam-
shaft.
Within specification  Replace the cylinder
head and the camshaft caps as a set.
Camshaft journal diameter
21.959–21.972 mm (0.8645–
0.8650 in)
EASB29B213
CHECKING THE TIMING CHAIN AND CAM-
SHAFT SPROCKET
1. Check:
• Timing chain
Damage/stiffness  Replace the timing
chain and camshaft as a set.
2. Check:
• Camshaft sprocket
More than 1/4 tooth wear "a"  Replace the
camshaft and the timing chain as a set.
b
1
a. 1/4 tooth
b. Correct
1. Timing chain roller
2. Camshaft sprocket
EASB29B214
CHECKING THE TIMING CHAIN TENSION-
ERS
1. Check:
• Timing chain tensioner
Crack/damage  Replace.
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a. While pressing the tensioner rod lightly with
your fingers, use a thin screwdriver "1" to
wind the tensioner rod up fully clockwise.
b. When releasing the screwdriver by pressing
lightly with your fingers, make sure that the
tensioner rod will come out smoothly.
c. If not, replace the tensioner assembly.
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5-15
CAMSHAFT
a
1
2