Yamaha F25A - Cylinder Inspection; Piston Inspection; Service Points

5-36
POWR
E
CRANKCASE, CRANKSHAFT ASSY., AND
CYLINDER BODY
SERVICE POINTS
Cylinder inspection
1. Measure:
● Cylinder bore
Out of specification → Rebore or
replace the cylinder.
NOTE:
Measure the cylinder bore in parallel and at
a right angle to the crankshaft. Then, aver-
age the measurements.
Standard
Wear
limit
Cylinder
bore “D”
65.000 ~ 65.015 mm
(2.5590 ~ 2.5596 in)
—
Taper
limit “T”
—
0.08 mm
(0.003 in)
Out of
round limit
—
0.08 mm
(0.003 in)
D = Maximum Dia. (D
1 ~ D6)
T = (maximum D
1 or D2) – (minimum D5
or D6)
Piston inspection
1. Measure:
● Piston diameter
Out of specification → Replace the
piston.
Distance
a
Piston diameter
Standard
2 mm
(0.07 in)
64.950 ~ 64.965 mm
(2.5570 ~ 2.5573 in)
Oversize piston diameter:
Oversize 1: + 0.25 mm (0.001 in)
(except for USA)
Oversize 2: + 0.50 mm (0.002 in)