Checking The Piston Pin; Checking The Piston Ring - Yamaha F40BMHD Service Manual

POWR
20 mm (0.8 in)
CRANKSHAFT AND PISTON
3. Calculate:
• Piston-to-cylinder clearance
Out of specification → Replace the
piston and piston rings, the cylinder
block or both.
Piston-to-
cylinder =
clearance
Piston-to-cylinder clearance
0.035 - 0.065 mm
(0.0014 - 0.0026 in)

CHECKING THE PISTON PIN

Measure:
• Piston pin diameter
Out of specification → Replace.
Piston pin diameter
15.965 - 15.970 mm
(0.6285 - 0.6287 in)

CHECKING THE PISTON RING

1. Measure:
• End gap
Out of specification → Replace the
piston rings as a set.
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)
NOTE:
Push the piston ring into the cylinder with
the piston crown.
5-43
Cylinder Piston
−
bore diameter
E