Yamaha F400A 2022 - Checking the Cylinder Bore; Checking the Piston Clearance; Checking the Piston Ring

Cylinder block
7-79
Checking the cylinder bore
1. Measure:
• Cylinder bore (D1–D6)
(at measuring points “a”, “b”, and “c”, and
in directions “d” [D1, D3, D5] and “e” [D2,
D4, D6])
Out of specification → Replace the cylin-
der block.
Checking the piston clearance
1. Measure:
• Piston diameter
See “Checking the piston diameter”
(7-78).
• Cylinder bore
See “Checking the cylinder bore” (7-79).
2. Calculate:
• Piston clearance
Out of specification → Replace the piston
or cylinder block.
Checking the piston ring
1. Measure:
• Piston ring dimension
Out of specification → Replace.
Piston
Diameter
95.945–95.960 mm (3.7774–
3.7779 in)
Limit
95.905 mm (3.7758 in)
Measuring point
14.5 mm (0.57 in)
a. 7.0 mm (0.28 in)
b. 52.0 mm (2.05 in)
c. 111.0 mm (4.37 in)
d. Parallel to the crankshaft
e. At a right angle to the crankshaft
Cylinder
Bore
96.000–96.012 mm (3.7795–
3.7800 in)
Limit
96.072 mm (3.7824 in)
a
b
c
d
e
D
1
D
2
D
3
D
4
D
5
D
6
Piston clearance = maximum cyl-
inder bore – piston outside diame-
ter
Piston clearance
0.040–0.067 mm (0.0016–
0.0026 in)
Limit
0.167 mm (0.0066 in)
a. Top ring
b. 2nd ring
c. Oil ring
c
b
a
B
T
T
B
T
B