It depends on what sort of bike you WANT. All shaft drives have a torque reaction, spline and seals problem, and they are costly and not light weight. Also engine speed clutches aren't as nice as when the clutch runs slower. No bike gearboxes are synchro meshed so the changes can be clunky. Fore to aft crank axis has a Bike reaction leaning effect and if the engine Locked up you wouldn't be able to stay on it. That illustrates the effect. I'm not saying engine lock ups are common, but they are NOT unknown. Nev