Yamaha F20A Service Manual page 42

SPEC
Item
Margin thickness (D)
Intake
Exhaust
Stem outside diameter
Intake
Exhaust
Guide inside diameter
Stem-to-guide clearance
Intake
Exhaust
Stem runout limit
VALVE SPRINGS
Free length
Free length limit
Tilt limit
PISTON(S)
Piston-to-cylinder clearance
Measuring point (D)
Standard
Oversize
Measuring point (H)
Pin boss inside diameter
Oversize piston diameter
1st (except for USA)
2nd
PISTON PIN(S)
Diameter
PISTON RINGS
Top ring
Type
Dimensions (B × T)
End gap (installed)
Wear limit
Side clearance (installed)
2nd ring
Type
Dimensions (B × T)
End gap (installed)
Wear limit
Side clearance (installed)
Oil ring
Dimensions (B × T)
End gap (installed)
MAINTENANCE SPECIFICATIONS
Worldwide
USA, CANADA
mm (in)
mm (in)
mm (in)
mm (in)
mm (in)
mm (in)
mm (in)
mm (in)
mm (in)
mm (in)
mm (in)
mm (in)
mm (in)
mm (in)
H
D
mm (in)
mm (in)
mm (in)
mm (in)
mm (in)
mm (in)
B
T
mm (in)
mm (in)
mm (in)
mm (in)
B
T
mm (in)
mm (in)
mm (in)
mm (in)
B
mm (in)
T
Unit
F20A
—
5.475 ~ 5.490 (0.2155 ~ 0.2161)
5.460 ~ 5.475 (0.2150 ~ 0.2155)
5.500 ~ 5.512 (0.2147 ~ 0.2170)
0.010 ~ 0.037 (0.0004 ~ 0.0015)
0.025 ~ 0.052 (0.0004 ~ 0.0015)
37.85 ~ 39.85 (1.491 ~ 1.569)
0.035 ~ 0.065 (0.0014 ~ 0.0026)
64.950 ~ 64.965 (2.5570 ~ 2.5573)
65.450 ~ 65.465 (2.5768 ~ 2.5774)
15.974 ~ 15.985 (0.6289 ~ 0.6293)
15.965 ~ 15.970 (0.6285 ~ 0.6287)
0.15 ~ 0.30 (0.006 ~ 0.012)
0.04 ~ 0.08 (0.002 ~ 0.003)
0.30 ~ 0.50 (0.012 ~ 0.020)
0.03 ~ 0.07 (0.001 ~ 0.003)
2.42 × 2.75 (0.095 × 0.108)
0.20 ~ 0.70 (0.008 ~ 0.028)
2-4
Model
0.6 ~ 1.0 (0.024 ~ 0.039)
0.7 ~ 1.1 (0.026 ~ 0.043)
0.016 (0.0006)
37.85 (1.49)
1.7 (0.06)
2 (0.007)
+ 0.25 (0.001)
+ 0.50 (0.002)
Rounded edge
1.2 × 2.4 (0.047 × 0.094)
0.5 (0.020)
Tapered edge
1.5 × 2.7 (0.591 × 0.106)
0.7 (0.028)
E
F25A
F25X