Transmission Reduction Ratios

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Columns are defined below:

Ratios
Transmission input shaft revolutions to 1 revolution of wheel.
Overall Min Reduction / Overall Max Reduction 
Crankshaft revolutions to 1 revolution of wheel.
Gear identification
Letters A, B, C, D in the diagram match table columns

DoubleReductionTransmissionGears.jpg

Ratio Formula
Total Gear Reduction = (B/A) * (D/C)


Double Gear Reduction Models

Model A B C D Ratio Variator Ratio Overall Min Reduction Overall Max Reduction
1983/84 NB50 Aero 14 33 13 44 7.978 2.4 - 1.2:1 9.58 19.17
1985 NB50 Aero 12 34 12 47 11.097 2.4 - 0.8:1 8.88 26.63
1986-87 NB50 Aero 12 34 12 47 11.097 2.4 - 0.8:1 8.88 26.63
87 SE50 A 13 34 12 47 10.244 2.4 - 0.8:1 8.19 24.58
87 SE50P A (restricted) 12 34 12 47 11.097 2.4 - 1.1:1 12.21 26.63
87 SE50P AA (restricted) 12 34 12 47 11.097 2.4 - 1.1:1 12.21 26.63
88-93 SA50 Elite 12 34 12 47 11.097 2.4 - 0.8:1 8.88 26.63
94-up SA50 Elite 12 42 13 45 12.115 2.45 - 0.85:1 10.30 29.68
SA50P (restricted) 12 42 13 45 12.115 2.40-1.15:1 13.93 29.08


Aftermarket gears giving the ratios listed have been reported in the below combinations. Full Thread


Aftermarket Gears A B C D Ratio Variator Ratio Overall Min Reduction Overall Max Reduction Notes
C & D gear swap (secondary) 12 42 15 42 9.80 2.45 - 0.85:1 8.33 24.01
12 42 16 42 9.19 2.45 - 0.85:1 7.81 22.51
12 42 16 41 8.97 2.45 - 0.85:1 7.62 21.97
12 42 17 41 8.44 2.45 - 0.85:1 7.18 20.68
12 42 18 41 7.97 2.45 - 0.85:1 6.78 19.53
12 42 18 39 7.58 2.45 - 0.85:1 6.45 18.58
12 42 19 37 6.82 2.45 - 0.85:1 5.79 16.70
12 42 20 36 6.30 2.45 - 0.85:1 5.36 15.44
A & B gear swap (primary) AF16 13 35 13 45 9.320 2.45 - 0.85:1 7.92 22.83
15 33 13 45 7.61 2.45 - 0.85:1 6.47 18.65
12 24 13 45 6.92 2.45 - 0.85:1 5.88 16.96
15 30 13 45 6.92 2.45 - 0.85:1 5.88 16.96
16 32 13 45 6.92 2.45 - 0.85:1 5.88 16.96
16 30 13 45 6.49 2.45 - 0.85:1 5.52 15.90
A & B gear swap (primary) AF05 16 32 12 47 7.83 2.40 - 0.80:1 6.27 18.80 Malossi 67-6458


Sym DD50

Aftermarket Gears A B C D Ratio Variator Ratio Overall Min Reduction Overall Max Reduction Notes
Stock DD50 Primary/Secondary 12 34 12 47 11.1 2.45 - 0.85:1 9.43 27.19
Stock DD50 Pri/ Dio stock Sec 12 34 13 45 9.81 2.45 - 0.85:1 8.34 24.03
This row & below, Stock DD50 Primary/Dio aftermarket gears 12 34 15 42 7.93 2.45 - 0.85:1 6.74 19.44
12 34 16 42 7.44 2.45 - 0.85:1 6.32 18.22
12 34 17 41 6.83 2.45 - 0.85:1 5.81 16.74
12 34 18 41 6.45 2.45 - 0.85:1 5.49 15.81
12 34 18 39 6.14 2.45 - 0.85:1 5.22 15.04
12 34 19 37 5.52 2.45 - 0.85:1 4.69 13.52
12 34 20 36 5.10 2.45 - 0.85:1 4.34 12.50



HondaSingleReductionXmission.jpg

Ratio Formula
Reduction = (B/A)


Single Gear Reduction Models

Model A B Ratio Pulley Ratio Overall Reduction
88 SB50, SB50P 13 83 6.385 1.8:1 11.49
1984-85 NQ50 A, AA Spree 12 83 6.917 1.8:1 12.45
1986-77 NQ50 A Spree 13 83 6.385 1.8:1 11.49
1986-87 NQ50 AA Spree 12 83 6.917 1.8:1 12.45
Aftermarket 15 81 5.40 1.8:1 9.72

-- Authors: Mousewheels, Wheelman, 808BMW

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