Checking The Piston Pin; Installing The Piston And Cylinder - Yamaha YZ450F Owner's Service Manual

TIP
The oil ring expander's end gap cannot be
measured. If the oil ring rail's gap is excessive,
replace all three oil rings.
Piston ring
Top ring
End gap (installed)
0.20–0.30 mm (0.0079–0.0118 in)
Limit
0.55 mm (0.0217 in)
2nd ring
End gap (installed)
0.35–0.50 mm (0.0138–0.0197 in)
Limit
0.85 mm (0.0335 in)
Oil ring
End gap (installed)
0.20–0.50 mm (0.0079–0.0197 in)

CHECKING THE PISTON PIN

EASB111229
1. Check:
• Piston pin
Blue discoloration/grooves  Replace the
piston pin and then check the lubrication
system.
2. Measure:
• Piston pin outside diameter "a"
Out of specification  Replace the piston
pin.
Piston pin outside diameter
17.991–18.000 mm (0.7083–
0.7087 in)
Limit
17.971 mm (0.7075 in)
CYLINDER AND PISTON
3. Measure:
• Piston pin bore inside diameter "b"
Out of specification  Replace the piston.
Piston pin bore inside diameter
18.004–18.015 mm (0.7088–
0.7093 in)
Limit
18.045 mm (0.7104 in)

INSTALLING THE PISTON AND CYLINDER

EASB111230
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.
5-36
b