Yamaha RS90GTZ Service Manual page 294

CONNECTING RODS AND PISTONS
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4. Install:
• Piston ring
(into the cylinder)
TIP
Level the piston ring in the cylinder with the
piston crown.
5.0 mm (0.20 in)
5. Measure:
• Piston ring end gap
Out of specification → Replace the piston
rings as a set.
TIP
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:
Top ring:
0.33 ~ 0.45 mm
(0.013 ~ 0.018 in)
2nd ring:
0.70 ~ 0.85 mm
(0.028 ~ 0.033 in)
Oil ring:
0.20 ~ 0.60 mm
(0.008 ~ 0.024 in)
6. Inspect:
• Piston pin
Blue discoloration/grooves → Replace the
piston pin and then check the lubrication
system.
7. Measure:
• Piston pin outside diameter
Out of specification → Replace the piston
pin.
Piston pin outside diameter:
18.991 ~ 19.000 mm
(0.7477 ~ 0.7480 in)
<Limit>: 18.971 mm (0.7469 in)
ENG