Checking The Piston Pin - Yamaha YFM250RX 2008 Service Manual

CYLINDER AND PISTON

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
Out of specification → Replace the piston
pin.
Piston pin outside diameter
16.991 ~ 17.000 mm
(0.6689 ~ 0.6693 in)
Limit
16.971 mm (0.6681 in)
3. Measure:
• Piston pin bore diameter
Out of specification → Replace the piston.
Piston pin bore inside diameter
17.002 ~ 17.013 mm
(0.6694 ~ 0.6698 in)
Limit
17.043 mm (0.6710 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
Piston pin outside diameter
Piston-pin-to-piston-pin-bore
clearance
0.002 ~ 0.022 mm
(0.0001 ~ 0.0009 in)
Limit
0.072 mm (0.0028 in)
4-36
ENG
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