Checking The Piston Pin - Yamaha MIO Service Manual

CYLINDER AND PISTON
Piston ring end gap
EAS00265

CHECKING THE PISTON PIN

1. Check:
• piston pin
Blue discoloration/grooves → Replace the
piston pin and then check the lubrication
system.
2. Measure:
• piston pin outside diameter a
Out of specification → Replace the piston
pin.
Piston pin outside diameter
3. Measure:
• piston pin bore diameter (of the piston) b
Out of specification → Replace the piston.
Piston pin bore diameter (of the
piston)
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
4 - 36
ENG
Top ring
0.10 ~ 0.25 mm (0.004 ~ 0.010 in)
<Limit>: 0.5 mm (0.020 in)
2nd ring
0.10 ~ 0.25 mm (0.004 ~ 0.010 in)
<Limit>: 0.6 mm (0.024 in)
Oil ring
0.20 ~ 0.70 mm (0.008 ~ 0.028 in)
14.995 ~ 15.000 mm
(0.5904 ~ 0.5906 in)
<Limit>: 14.975 mm (0.5896 in)
15.002 ~ 15.013 mm
(0.5906 ~ 0.5911 in)
<Limit>: 15.043 mm (0.5922 in)
0.002 ~ 0.018 mm
(0.0001 ~ 0.0007 in)
<Limit>: 0.068 mm (0.0027 in)