High-Ratio Differential Carrier

High-powered sportbikes often have an incredibly long first gear compared to the following five, mostly to combat front wheel lift. In the case of a stock ZX12R, redline in first gear is approximately 90 mph!  

I needed a solution to reduce the final drive ratio enough to not burn the clutch when moving from a standstill. The final drive ratio in this arrangement is 5.2:1 allowing for rapid starts while saving clutch material. A two-chain solution with independent tensioning was required to get this amount of reduction while maintaining CV clearance.

This design is a clean-sheet approach to mating a motorcycle output chain to an automotive limited slip differential. The main structure is made entirely with 2D manufacturing operations (laser and plasma cutting) and a few off-axis holes which were done by hand. 

Overall gear ratio is easily changed by swapping out the unit's input gear. This requires a change in chain length and re-tensioning of the unit, but everything is easily accessible and only one bolt needs to be loosened.