This is not correct. The (very old) rules of MX racing allowed 450cc 4-strokes to race with 250cc 2-strokes, but back in the day before 4-strokes were developed 2-strokes had such a weight advantage that 4-strokes were not competitive. FF several years, 4-strokes developed and got much more powerful and much lighter, not to mention made better power, and (in 1998 I believe..) Yamaha entered the series with the first hand-made YZ400 4-stroke and promptly won the championship. Horsepower wars drove the engines up to the 450cc limit allowed by the race series (read: marketing) and now the 4-strokes make so much power that the 2-strokes of the allowed displacement don't have a chance. I've ridden both, and 4-strokes are soooo much more fun to ride! I'm never going back 2-stroke. It would be really cool to see similar development for RC, but I don't know if there's enough cash to make it happen?