Yamaha YB50 - Piston Pin and Piston Pin Bearing

ENG
INSPECTION AND REPAIR
4-14
3. Measure:
• Gap between ends
Outside specified value

Change set
of rings.
Use a thickness gauge .
a Measurement point 20 mm (0.8 in)
4. Clearance of piston rings:
The size of the rings is not stamped on its
upper part.
PISTON PIN AND PISTON PIN BEARING
1. Inspect:
Piston pin
Blue discolouring/Groove

Change, then
inspect the lubrication system.
2. Measure:
• External diameter
a (Piston pin clip)
Outside specified value

Change
3. Measure:
• Clearance of piston pin to piston:
Outside specified value

Change the
piston
Clearance of piston pin to piston
0.004 ~ 0.016 mm
Limit
0.07 mm
Standard Limit
Top ring 0.15~0.35 mm 0.60 mm
Second ring 0.15~0.35 mm 0.60 mm
Clearance of piston pin to piston=
Size of inner diameter (Piston pin)
b -
External diameter (piston pin housing) 
a
External diameter (piston pin clip)
9.996 ~ 10.00 mm
Piston ring clearance
1st Clearance 40.25 mm
2st Clearance 40.50 mm