What is the most expensive and complex part of a motorcycle? It's likely that you have the answer wrong. The correct answer is the engine's center cases. A modern motorcycle is designed around its engine center cases.
If the engine center cases are spot-on, a motorcycle manufacturer might be able to get eight to ten years out of them, all future development can focus on the frame, cylinder, fueling, ignition, clutch, bodywork and suspension. If the the engine center cases are correct from the beginning a motorcycle manufacturer will be able to turn a profit over the life of the engine molds.
During the life span of the engine center case, the motorcycle-manufacturer's product manager must continuously monitor sales, public opinion and engine developments. He has to have his finger on the pulse of the remaining life in the engine's center cases.
Why? Because it takes two to three years for a motorcycle design department to come up with three-dimensional drawings, models and sand cast samples of a new motorcycle engine. After the drawings, models and samples, it often takes two-years and several refined versions of prototype built engine center cases before the preproduction (or pre-pro) starts. The motorcycles build from these preproduction are supposed to be identical to the soon-to-be produced production motorcycles, some aspects are still in flux. The tires, gearing, fuel, ignition and suspension settings can still be changed at this stage. Once the final decisions are made, the manufactures test team will get into the play.