Checking The Piston Pin; Checking The Timing Chain Guide; Installing The Piston And Cylinder - Yamaha 2010 XMAX YP125R Service Manual

3. Measure:
• Piston ring end gap
Out of specification → Replace the piston
ring.
TIP
The oil ring expander spacer end gap cannot be
measured. If the oil ring rail gap is excessive, re-
place all three piston rings.
Piston ring
Top ring
End gap (installed)
0.15–0.30 mm (0.0059–0.0118
in)
Limit
0.55 mm (0.0217 in)
2nd ring
End gap (installed)
0.30–0.45 mm (0.0118–0.0177
in)
Limit
0.80 mm (0.0315 in)
Oil ring
End gap (installed)
0.20–0.70 mm (0.0079–0.0276
in)
EAS24440

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.
Piston pin outside diameter
16.991–17.000 mm (0.6689–
0.6693 in)
Limit
16.971 mm (0.6681 in)
CYLINDER AND PISTON (YP250R)
3. Measure:
• Piston pin bore diameter "b"
Out of specification → Replace the piston.
Piston pin bore inside diameter
17.004–17.015 mm (0.6694–
0.6699 in)
Limit
17.045 mm (0.6711 in)
4. Calculate:
• Piston-pin-to-piston-pin-bore clearance
Out of specification → Replace the piston pin
and piston as a set.
• Piston-pin-to-piston-pin-bore clearance =
Piston pin bore diameter "b" -
Piston pin outside diameter "a"
Piston-pin-to-piston-pin-bore
clearance
0.004–0.024 mm (0.0002–0.0009
in)
EAS37P1065

CHECKING THE TIMING CHAIN GUIDE

1. Check:
• Timing chain guide (exhaust side)
Damage/wear → Replace.
EAS24450

INSTALLING THE PISTON AND CYLINDER

1. Install:
• Top ring "1"
• 2nd ring "2"
• Upper oil ring rail "3"
• Oil ring expander "4"
• Lower oil ring rail "5"
TIP
Be sure to install the piston rings so that the
manufacturer marks or numbers face up.
5-87