Checking The Piston Rings; Checking The Piston Pin - Yamaha R15 2022 Service Manual

b. 6.0 mm (0.24 in) from the bottom edge of the
piston
Piston
Diameter
57.962–57.985 mm (2.2820–
2.2829 in)
d. If out of specification, replace the piston
and piston rings as a set.
e. Calculate the piston-to-cylinder clearance
with the following formula.
• Piston-to-cylinder clearance =
Cylinder bore "C" -
Piston skirt diameter "D"
Piston-to-cylinder clearance
0.015–0.048 mm (0.0006–0.0019
in)
f. If out of specification, replace the cylinder,
and replace the piston and piston rings as
a set.
EAS30292

CHECKING THE PISTON RINGS

1. Measure:
• Piston ring side clearance
Out of specification → Replace the piston
and piston rings as a set.
TIP
Before measuring the piston ring side clearance,
eliminate any carbon deposits from the piston
ring grooves and piston rings.
Piston ring
Top ring
Side clearance limit
0.115 mm (0.0045 in)
2nd ring
Side clearance limit
0.115 mm (0.0045 in)
CYLINDER AND PISTON
2. Install:
• Piston ring
(into the cylinder)
TIP
Level the piston ring into the cylinder with the
piston crown.
a. 40 mm (1.57 in)
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.
EAS30293

CHECKING THE PISTON PIN

1. Check:
• Piston pin
Blue discoloration/grooves → Replace the
piston pin and then check the lubrication sys-
tem.
5-29
ENG
Piston ring
Top ring
End gap limit
0.50 mm (0.0197 in)
2nd ring
End gap limit
0.85 mm (0.0335 in)
a