Yamaha Wolverine YX70EPNG, Service Manual

Page: 234 / 503

CYLINDER HEAD, CYLINDER, AND PISTON
5-21
EBS30439
CHECKING THE CYLINDER HEAD
1. Eliminate:
• Combustion chamber carbon deposits
(with a rounded scraper)
NOTICE
ECB01851
Do not use a sharp instrument; otherwise,
the following may be damaged or scratched:
• Spark plug bore threads
• Valve seats
2. Check:
• Cylinder head
Damage/scratches
→
Replace.
• Cylinder head water jacket
Mineral deposits/rust
→
Eliminate.
3. Measure:
• Cylinder head warpage
Out of specification
→
Resurface the cylinder
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 cylinder
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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EBS30147
CHECKING THE CYLINDER AND PISTON
1. Check:
• Piston wall
• Cylinder wall
Vertical scratches
→
Replace the cylinder,
and replace the piston and piston rings as a
set.
2. Measure:
• Piston-to-cylinder clearance
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a. Measure the cylinder bore “C” with the cylin-
der bore gauge.
TIP
Measure the cylinder bore “C” by taking side-to-
side and front-to-back measurements of the cyl-
inder.
Warpage limit
0.03 mm (0.0012 in)
2
1
Bore
103.000–103.020 mm (4.0551–
4.0559 in)
Wear limit
103.080 mm (4.0583 in)
Taper limit
0.050 mm (0.0020 in)
Out of round limit
0.050 mm (0.0020 in)
“C” = maximum of D
1
, D
2
, D
3
, D
4
, D
5
, D
6
Taper (front-to-back) = maximum difference be-
tween D
1
, D
3
, D
5
Taper (side-to-side) = maximum difference be-
tween D
2
, D
4
, D
6
Out of round (top) = difference between D
1
, D
2
Out of round (middle) = difference between D
3
,
D
4
Out of round (bottom) = difference between D
5
,
D
6