Checking The Piston Pin - Yamaha YXR70FX Service Manual

CYLINDER AND PISTON
Piston ring end gap
Top ring
0.20 ~ 0.35 mm
(0.008 ~ 0.014 in)
<Limit>: 0.60 mm (0.024 in)
2nd ring
0.75 ~ 0.90 mm
(0.030 ~ 0.035 in)
<Limit>: 1.25 mm (0.049 in)
Oil ring
0.20 ~ 0.70 mm
(0.008 ~ 0.028 in)
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
22.991 ~ 23.000 mm
(0.9052 ~ 0.9055 in)
<Limit>: 22.971 mm (0.9044 in)
3. Measure:
• piston pin bore inside diameter b
Out of specification → Replace the piston.
Piston pin bore inside diameter
23.004 ~ 23.015 mm
(0.9057 ~ 0.9061 in)
<Limit>: 23.045 mm (0.9073 in)
4 - 40
ENG