Yamaha YB50, Service Manual

Page: 64 / 161

ENG
INSPECTION AND REPAIR
4-13
• If this is outside the specified value change
the piston and the set of rings.
Third step:
• Calculate the clearance of the piston to the
cylinder using the following formula:
• If this is outside the specified value, rectify
or change the cylinder and change the pis-
ton and set of rings.
PISTON RINGS
1. Measurement:
• Lateral clearance Outside specified value
Change the piston and/or rings. Use
a thickness gauge .
2. Install:
• Piston rings on the cylinder
Press the ring and the piston crown
together.
Size of the piston P
Standard 39.952 ~ 39.997 mm
1st Clearance 40.25 mm
2st Clearance 40.50 mm
Clearance of piston to cylinder =
Inner diameter of cylinder “C” –
Diameter of piston skirt “P”
Cylinder-piston clearance
0.034 ~ 0.047 mm
Limit
0.1 mm
Standard Limit
Top ring 0.03~0.05 mm 0.10 mm
Second ring 0.03~0.05 mm 0.10 mm