Observing outdoor motocross and supercross in the U.S. over the past several years, and noting recent developments (since the introduction of several 250 four-stroke motocrossers), I have concluded that four-strokes are considered the weapon of choice in the 125 class for supercross, but two-strokes rule the 125 class outdoors. The opposite is true in the 250 class, where four-strokes are finally taking charge outdoors (particularly, in Europe, but also with Kevin Windham leading the way in the United States), but two strokes are still dominant indoors for supercross.
Many people fail to realize that 125cc two-strokes tend to make more peak horsepower than 250cc four-strokes, particularly, when modified. The 250cc four-strokes have a huge torque advantage, however, and this is most evident on a tight, supercross track.
Then why are the top riders still choosing to ride two-strokes in 250cc supercross competition? Why are the four-strokes seemingly more competitive outdoors in the bigger class? It seems strange, but accurate, nonetheless.
Perhaps, this year’s crop of 250cc four-strokes will make their mark in outdoor competition (Yamaha has never won an AMA Outdoor title with the YZ250F, but has won at least two Supercross titles with that bike). Nevertheless, the 125cc two-strokes, even this year, appear to be capable of higher peak horsepower than the 250cc four-strokes and, of course, they are significantly lighter. We will see.