Yamaha YBR250 2007, Service Manual

Page: 224 / 361

ENG
CHECKING THE PISTON PIN
1. Check:
• piston pin
Blue discoloration/grooves --> Replace the
pin and check the lubrication system.
2. Measure:
• piston pin outside diameter
a
Out of specification --> Replace.
Piston pin outside diameter
16.991 ~ 17.000 mm
(0.6689 ~ 0.6692 in)
<Limit>: 16.970 mm (0.6681 in)
3. Measure:
• piston pin bore diameter
b
Out of specification --> Replace the piston.
4. Measure:
• clearance between the pin bore and the
piston pin
Out of specification
--> Replace the piston
pin and piston as a set.
Piston pin bore diameter
17.002 ~ 17.013 mm
(0.6694 ~ 0.6698 in)
<Limit>: 17.043 mm (0.6709 in)
Piston-pin-to-piston clearance = (piston pin
bore diameter
b b
b b
b
) - (piston pin outside
diameter
a a a a a
)
Piston-pin-to-piston clearance
0.010 ~ 0.025 mm
(0.0004 ~0.0010 in)
<Limit>: 0.015 mm (0.0006 in)
a
b
CYLINDER AND PISTON
5-34