FastCounter by bCentral

1.

Find your bore size in Column 1.

2.

Move right to Column 2 to the exact size for boring (decimal) 

3.

Select your stroke in Columns 3 through 9

Bore Size
(Relative)

Bore Size
(Absolute)

Std. EL
3-1/2"
3.50"

Std. FL
3-31/32"
3.96875"

80" FL
4-1/4"
4.250"

U Stroke
4-9/32"
4.28125"

S&S
4-1/2"
4.500"

S&S
4-5/8"
4.625"

S&S
4-3/4"
4.750"

Std. 61"

3.3125"

60.33

68.40

73.25

73.79

77.56

79.72

81.87

+.010

3.3225

60.69

68.82

73.70

74.24

78.03

80.20

82.37

.020

3.3325

61.06

69.23

74.14

74.68

78.50

80.68

82.86

.030

3.3425

61.42

69.65

74.59

75.13

78.97

81.17

83.36

.040

3.3525

61.79

70.07

75.03

75.58

79.45

81.65

83.86

.050

3.3625

62.16

70.49

75.48

76.04

79.92

82.14

84.36

.060

3.3725

62.53

70.91

75.93

76.49

80.40

82.63

84.86

.070

3.3825

62.90

71.33

76.38

76.94

80.87

83.12

85.37

.080

3.3925

63.27

71.75

76.83

77.40

81.35

83.61

85.87

.090

3.4025

63.65

72.17

77.29

77.86

81.83

84.11

86.38

.100

3.4125

64.02

72.60

77.74

78.31

82.31

84.60

86.89

Std. 74"

3.4375

64.96

73.66

78.89

79.47

83.53

85.85

88.17

+.010

3.4475

65.34

74.09

79.34

79.93

84.01

86.35

88.68

.020

3.4575

65.72

74.52

79.81

80.39

84.50

86.85

89.19

.030

3.4675

66.10

74.96

80.27

80.86

84.99

87.35

89.71

.040

3.4775

66.48

75.39

80.73

81.33

85.48

87.86

90.23

.050

3.4875

66.87

75.82

81.20

81.79

85.97

88.36

90.75

Std. 80"

3.498

67.27

76.28

81.69

82.29

86.49

88.89

91.30

+.010

3.508

67.66

76.72

82.15

82.76

86.99

89.40

91.82

.020

3.518

68.04

77.16

82.62

83.23

87.48

89.91

92.34

.030

3.528

68.43

77.59

83.09

83.70

87.98

90.43

92.87

.040

3.538

68.82

78.04

83.57

84.18

88.48

90.94

93.40

.050

3.548

69.21

78.48

84.04

84.66

88.98

91.45

93.93

.060

3.558

69.60

78.92

84.51

85.13

89.48

91.97

94.46

S&S

3.625

72.24

81.92

87.73

88.37

92.89

95.47

98.05

All 1936-52 E, EL" motors are the same bore size

(probably also applies to JD-type 61" motors 1915-29)

+.100" is the largest commercially-available EL piston oversize

3.50" std. stroke, all 1915-52 E, EL 61" flywheels including JD-types

3.96875" std. stroke, all 1941-83 F, FL, FLH, FX etc. 74" flywheels

4.25" std. stroke, all 1978-* FLH, FX etc. 80" flywheels

4.28125" std. stroke, all 1937-48 U, UL, UH & ULH flywheels

S&S cylinder is Sidewinder (3-5/8")

"Harley-Davidson" name for reference purposes only. Not affiliated with Harley-Davidson Motor Co.

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