Checking The Piston Rings - Yamaha 2004 YP400 Service Manual

CYLINDER AND PISTON
EAS00263

CHECKING THE PISTON RINGS

1. Measure:
• piston ring side clearance
Out of specification → Replace the piston
and piston rings as a set.
NOTE:
_
Before measuring the piston ring side clear-
ance, eliminate any carbon deposits from the
piston ring grooves and piston rings.
Piston ring side clearance
2. Install:
• piston ring
(into the cylinder)
NOTE:
_
Level the piston ring into the cylinder with the
piston crown.
a 40 mm (1.6 in)
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.
Piston ring end gap
5 - 33
ENG
Top ring
0.030 ~ 0.070 mm
(0.0012 ~ 0.0028 in)
<Limit>: 0.100 mm (0.0039 in)
2nd ring
0.020 ~ 0.055 mm
(0.0008 ~ 0.0022 in)
<Limit>: 0.100 mm (0.0039 in)
Top ring
0.20 ~ 0.35 mm
(0.0079 ~ 0.0138 in)
<Limit>: 0.50 mm (0.0197 in)
2nd ring
0.40 ~ 0.55 mm
(0.0157 ~ 0.0217 in)
<Limit>: 0.80 mm (0.0315 in)
Oil ring
0.10 ~ 0.40 mm
(0.0039 ~ 0.0157 in)