Yamaha RAPTOR YFM125RA, Service Manual, Page: 172 / 300

CYLINDER HEAD
5-9
3. Measure:
• Cylinder head warpage
Out of specification
→
Resurface the cyl-
inder head.
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a. Place a straightedge “1” and a thickness
gauge “2” across the cylinder head.
b. Measure the warpage.
c. If the limit is exceeded, resurface the cylin-
der head as follows.
d. Place a 400–600 grit wet sandpaper on the
surface plate and resurface the cylinder
head using a figure-eight sanding pattern.
TIP
To ensure an even surface, rotate the cylinder
head several times.
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EAS00212
CHECKING THE TAPPET COVERS AND
CAMSHAFT SPROCKET COVER
The following procedure applies to both of the
tappet covers.
1. Check:
• Tappet covers
• Camshaft sprocket cover
Damage/wear
→
Replace the defective
part(s).
EAS24180
CHECKING THE CAMSHAFT SPROCKET
1. Check:
• Camshaft sprocket
More than 1/4 tooth wear “a”
→
Replace
the camshaft sprocket and the timing
chain as a set.
EAS24200
CHECKING THE TIMING CHAIN TEN-
SIONER
1. Check:
• Timing chain tensioner
Cracks/damage/rough movement
→
Replace.
2. Check:
• One-way cam operation
Rough movement
→
Replace the timing
chain tensioner assembly.
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a. Lightly press the timing chain tensioner rod
into the timing chain tensioner housing by
hand.
TIP
While pressing the timing chain tensioner rod,
wind it clockwise with a thin screwdriver “1”
until it stops.
b. Remove the screwdriver and slowly release
the timing chain tensioner rod.
c. Make sure that the timing chain tensioner
rod comes out of the timing chain tensioner
housing smoothly. If there is rough move-
ment, replace the timing chain tensioner.
Warpage limit
0.03 mm (0.0012 in)
a. 1/4 tooth
b. Correct
1. Timing chain
2. Camshaft sprocket