that's what i always thought from the 2 strokes i've ridden and from what i've seen. the 4 stroke equivalent of a 2 stroke always seems to be about twice the size. 125 2 stroke = 250 4 stroke, 250 2 stroke = 450/500 4 stroke... sort of like that is how i see it.
yeah thats a pretty close comparison without going into serious detail and debate..