Yamaha F115A - Calculating the Piston-To-Cylinder Clearance; Checking the Piston Ring

5-39
POWR
E
CRANKSHAFT AND PISTON/
CONNECTING ROD ASSEMBLY
CALCULATING THE PISTON-TO-
CYLINDER CLEARANCE
5
Calculate:
• Piston-to-cylinder clearance
Out of specification → Replace the pis-
ton and piston rings, the cylinder
block or both.
Piston-to-
cylinder
clearance
=
Cylinder
bore
–
Piston
diameter
Piston-to-cylinder clearance
0.070 - 0.080 mm
(0.0028 - 0.0031 in)
CHECKING THE PISTON RING 5
1. Measure:
• End gap a
Out of specification → Replace the pis-
ton rings as a set.
NOTE:
Push the piston ring into the cylinder with
the piston crown.
End gap (installed)
Top ring
0.15 - 0.30 mm
(0.006 - 0.012 in)
2nd ring
0.70 - 0.90 mm
(0.028 - 0.035 in)
Oil ring
0.20 - 0.70 mm
(0.008 - 0.028 in)
5480