The poppet valve is almost universally used in all forms of transport powered by an internal combustion engine. Motorsport has always had a buoyant two-stroke sector in the motorcycle arena, although this is on the wane now with Grand Prix motorcycle racing having bidden farewell to its last two-stroke class at the end of 2011. So, we have confined ourselves to a four-stroke future, and this generally means poppet valves. Brave attempts by forward-thinking engineers over the generations to...