Piston-To-Cylinder Clearance; Piston Pin Inspection; Piston Ring Inspection - Yamaha F20A Service Manual

POWR
CRANKCASE, CRANKSHAFT ASSY., AND
CYLINDER BODY

Piston-to-cylinder clearance

1. Calculate:
Piston-to-cylinder clearance
Out of specification → Replace the
piston and piston rings, the cylinder
or both.
Piston-to-
cylinder =
clearance
Piston-to-cylinder clearance:
0.035 ~ 0.065 mm
(0.0014 ~ 0.0026 in)

Piston pin inspection

1. Measure:
Piston pin diameter
Out of specification → Replace the
piston pin.
Piston pin diameter:
15.965 ~ 15.970 mm
(0.6285 ~ 0.6287 in)

Piston ring inspection

1. Measure:
End gap a
Out of specification → Replace the
piston ring.
End gap (installed):
Top piston ring:
0.15 ~ 0.30 mm
(0.006 ~ 0.012 in)
2nd piston ring:
0.30 ~ 0.50 mm
(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.
5-37
Cylinder Piston
–
bore diameter
E