Yamaha XV19SX(C), Service Manual

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CYLINDERS AND PISTONS
5-51
3. Measure:
• Piston ring end gap
Out of specification
→
Replace the piston
ring.
NOTE:
The oil ring expander spacer’s end gap cannot
be measured. If the oil ring rail’s gap is exces-
sive, replace all three piston rings.
EAS24440
CHECKING THE PISTON PINS
The following procedure applies to all of the pis-
ton pins.
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.
4. Calculate:
• Piston-pin-to-piston-pin-bore clearance
Out of specification
→
Replace the piston pin
and piston as a set.
EAS24460
INSTALLING THE PISTONS AND
CYLINDERS
The following procedure applies to all of the pis-
tons and cylinders.
1. Install:
• Top ring “1”
• 2nd ring “2”
• Lower oil ring rail “3”
• Upper oil ring rail “4”
• Oil ring expander “5”
Piston ring
Top ring
End gap (installed)
0.20–0.35 mm (0.0079–0.0138
in)
Limit
0.55 mm (0.0217 in)
2nd ring
End gap (installed)
0.45–0.60 mm (0.0177–0.0236
in)
Limit
0.95 mm (0.0374 in)
Oil ring
End gap (installed)
0.20–0.70 mm (0.0079–0.0276
in)
Piston pin outside diameter
22.991–23.000 mm (0.9052–
0.9055 in)
Limit
22.971 mm (0.9044 in)
Piston pin bore inside diameter
23.004–23.015 mm (0.9057–
0.9061 in)
Limit
23.045 mm (0.9073 in)
• 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 (0.00016–
0.00094 in)