I dont quite understand when people say 250r are so powerful and fast , how? I HEARD in another forum someone say" if u want the power of a 250r get a 400 ex" , how is a 250cc just as powerful as a 400cc?

The 250r is a 2 stroke and the 400ex is a 4 stroke. 2 strokes are more powerful than a 4 stroke of the same cc's so it takes a 4 stroke with more cc's to equal a 2 stroke.

Stock the 250R is around 34-35HP and the 400EX is around 32-33 HP, but there are not many stock 250Rs out there, most put out at least 40HP with the thinner head gasket and a pipe, whereas it costs much more to get that power from the 4-stroke 400EX, so less people do it.

Rod 250R

Actually, the 400ex has 28hp...and the 250R is around 35hp.