Lets keep the number one factor in mind of why the MX world made the switch and manufactures were forced to develop the 4 strokes... The EPA mandate that 2 strokes were to dirty to be used in the motorcycle and off-road areas. It happened to snowmobiles as well. This forced the manufactures to look at increasing the performance of the 4 strokes to where they are today. The ability and technology is there but until it is forced to be developed it will not happen...