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The following is based on information taken from the Cycleserv publication: Norton Commando ‘S’ Type, Roadster, Fastback (Page 66). It is based on standard gear ratios and sprockets with 19” wheels and a 4.10 section rear tyre. The only variable is the number of teeth on the gearbox sprocket. My Commando is now fitted with a 20 tooth gearbox sprocket, down from the 22 tooth sprocket with which it came.
1. Number of Gearbox Sprocket Teeth = 19 and Top Gear Ratio = 4.84:1 = 15.429 mph/1,000 revs in Top Gear (or 24.857 km/h). It = 108 mph @ 7,000 rpm.
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Fourth Gear
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Third Gear
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Second Gear
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Revs
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Mph
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Mph
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Mph
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1,500
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23.14
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19.07
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13.50
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2,000
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30.86
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25.42
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18.00
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2,500
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38.57
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31.78
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22.50
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3,000
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46.29
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38.13
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27.00
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3,500
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54.00
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44.49
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31.50
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4,000
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61.72
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50.84
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36.00
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4,500
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69.43
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57.19
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40.50
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5,000
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77.15
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63.55
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45.00
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5,500
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84.86
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69.91
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49.50
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6,000
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92.57
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76.26
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54.00
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6,500
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100.29
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82.62
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58.50
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7,000
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108.00
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88.97
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63.00
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2. Number of Gearbox Sprocket Teeth = 20 and Top Gear Ratio = 4.60:1 = 16.286 mph/1,000 revs in Top Gear (or 26.286 km/h). It = 114 mph @ 7,000 rpm.
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Fourth Gear
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Third Gear
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Second Gear
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Revs
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Mph
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Mph
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Mph
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1,500
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24.43
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20.14
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14.35
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2,000
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35.57
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26.86
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19.14
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2,500
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40.72
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33.58
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23.93
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3,000
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48.86
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40.29
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28.72
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3,500
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57.00
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47.00
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33.50
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4,000
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65.14
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53.72
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38.28
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4,500
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73.29
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60.44
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43.07
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5,000
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81.43
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67.15
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47.86
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5,500
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89.57
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73.87
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52.64
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6,000
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97.72
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80.58
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57.43
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6,500
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105.86
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87.29
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62.21
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7,000
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114.00
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94.00
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67.00
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3. Number of Gearbox Sprocket Teeth = 21 and Top Gear Ratio = 4.38:1 = 17.000 mph/1,000 revs in Top Gear (or 27.286 km/h). It = 119 mph @ 7,000 rpm.
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Fourth Gear
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Third Gear
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Second Gear
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Revs
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Mph
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Mph
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Mph
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1,500
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25.50
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21.21
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15.00
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2,000
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34.00
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28.28
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20.00
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2,500
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42.50
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35.35
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25.00
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3,000
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51.00
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42.42
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30.00
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3,500
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59.50
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49.49
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35.00
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4,000
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68.00
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56.56
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40.00
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4,500
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76.50
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63.63
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45.00
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5,000
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85.00
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70.70
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50.00
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5,500
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93.50
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77.77
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55.00
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6,000
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102.00
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84.84
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60.00
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6,500
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110.50
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91.91
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65.00
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7,000
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119.00
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99.00
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70.00
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Perce Butterworth
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