Yamaha Wolverine YX70EPNG, Service Manual

Page: 236 / 503

CYLINDER HEAD, CYLINDER, AND PISTON
5-23
EBS30149
CHECKING THE PISTON PIN
1. Check:
• Piston pin
Blue discoloration/grooves
→
Replace the
piston pin, and then check the lubrication sys-
tem.
2. Measure:
• Piston pin outside diameter “a”
Out of specification
→
Replace the piston pin.
3. Measure:
• Piston pin bore diameter “b”
Out of specification
→
Replace the piston.
EBS30150
INSTALLING THE PISTON AND CYLINDER
1. Install:
• Oil ring expander “1”
• Lower oil ring rail “2”
• Upper oil ring rail “3”
• 2nd ring “4”
• Top ring “5”
TIP
Be sure to install the piston rings so that the
manufacturer’s marks or numbers face up.
2. Install:
• Piston “1”
• Piston pin “2”
• Piston pin clips “3”
TIP
• Apply engine oil to the piston pin.
• Make sure the manufacturer’s mark “a” on the
piston points towards the AC magneto side.
• Install the piston pin from the side of the piston
that has the manufacturer’s mark “a”.
• Before installing the piston pin clips, cover the
crankcase opening with a clean rag to prevent
the clips from falling into the crankcase.
3. Install:
• Cylinder gasket
• Dowel pins
4. Lubricate:
• Piston
• Piston rings
• Cylinder
(with the recommended lubricant)
Top ring
End gap (installed) limit
0.50 mm (0.0197 in)
2nd ring
End gap (installed) limit
0.70 mm (0.0276 in)
Oil ring
End gap (installed) limit
1.0 mm (0.039 in)
Piston pin outside diameter limit
22.974 mm (0.9045 in)
Piston pin bore inside diameter
limit
23.035 mm (0.9069 in)
b
1
2
New
1
2
3
a
New
New