Thursday, 12 April 2012

Final drive ratios

While i have the scout on the lift, i decided to take note of some figures, to gelp get the best out of the stroker motor. I know that these figures will give me only theoretical top speeds etc but its good to know what gearing changes will do to your rev/speed ratio once you are on the road.
First off, with the cylinders fitted set the rear piston to tdc and put a chalk mark on the rear tyre, selected 1st gear and rotated the wheel for one full revolution of the crank... measured the distance travelled, same again for 2nd and top gear.

The Scout is fitted with a 24t gearbox/trans sprocket and a BSA qd rear wheel with a 49t sprocket giving a final drive ratio of 2.04:1

The BSA hub won't give me much scope for sprocket changes, so I'm thinking of changing to a Honda CB72e rear hub, with the advantage of a TLS rear brake, to let me try a range of sprocket sizes.... I reckon an FDR of 1.5:1 should work with the motor without losing too much acceleration

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