Yamaha YJ50RAP Service Manual page 129

CYLINDER HEAD, CYLINDER AND PISTON
2. Measure:
• piston pin outside diameter a
Out of specification → Replace the piston pin.
Piston pin outside diameter
9.996 ~ 10.000 mm
(0.3935 ~ 0.3937 in)
<Limit>: 9.976 mm (0.3928 in)
3. Measure:
• piston pin bore diameter (in the piston) 1
Out of specification → Replace the piston
pin.
Piston pin bore diameter (in the
piston)
10.004 ~ 10.015 mm
(0.3939 ~ 0.3943 in)
<Limit>: 10.045 mm (0.3955 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 a
Piston-pin-to-piston clearance
0.004 ~ 0.019 mm
(0.00016 ~ 0.00075 in)
<Limit>: 0.069 mm (0.0027 in)
5. Check:
• bearing
Damage/pitting → Replace.
5 - 10
ENG