Checking The Piston Pin - Yamaha YFM50S Service Manual

CYLINDER AND PISTON
EBS00251

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
12.996 ~ 13.000 mm
(0.5117 ~ 0.5118 in)
<Limit>: 12.976 mm (0.5109 in)
3. Measure:
• piston pin bore diameter b
Out of specification → Replace the piston.
Piston pin bore diameter
13.002 ~ 13.013 mm
(0.5119 ~ 0.5123 in)
<Limit>: 13.043 mm (0.5135 in)
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 clearance
0.002 ~ 0.017 mm
(0.00008 ~ 0.00067 in)
<Limit>: 0.067 mm (0.00264 in)
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ENG