I know that in motocycles that fourstokes usually have to have 2 times as much displacment to make the same power as a 2 stroke. They let four stroke 250s race 125 2 strokes. So how can a 250EX that is a four stroke be around the same speed as the trail blazer 250 that is a 2 stroke.

 

Because the trail blazer uses a very low tech engine, no reed valve, just ports. Also the 250ex is much lighter than the trail blazer.

 

The TrailBlazer engine is also built ot last more than one season. It turns a lower rpm than all motocross two strokes. Also weighs twice as much.

 

You also have to remeber that the trail blazer is an automatic which usually gives up a little top end over a manual or semi auto, like on the ex.