Yamaha F40BMHD, Service Manual

Page: 254 / 537

POWR
5-43
CRANKSHAFT AND PISTON
E
3. Calculate:
• Piston-to-cylinder clearance
Out of specification
→
Replace the
piston and piston rings, the cylinder
block or both.
CHECKING THE PISTON PIN
Measure:
• Piston pin diameter
Out of specification
→
Replace.
CHECKING THE PISTON RING
1. Measure:
• End gap
Out of specification
→
Replace the
piston rings as a set.
NOTE:
Push the piston ring into the cylinder with
the piston crown.
Piston-to-
cylinder
clearance
=
Cylinder
bore
−
Piston
diameter
Piston-to-cylinder clearance
0.035 - 0.065 mm
(0.0014 - 0.0026 in)
20 mm (0.8 in)
Piston pin diameter
15.965 - 15.970 mm
(0.6285 - 0.6287 in)
End gap (installed)
Top ring
0.15 - 0.30 mm
(0.006 - 0.012 in)
2nd ring
0.30 - 0.50mm
(0.012 - 0.020 in)
Oil ring
0.20 - 0.70 mm
(0.008 - 0.028 in)