i rode with a friend who has a Scrambler 400 4x4, and i was pretty impressed by it.
in a short drag, i only beat it by a few bike-lengths. i think the only downside is the wieght. the scrambler is pushing 500 lbs. and it was pretty noticeable when he jumped it.
but it did seem to have a lot more power than i expected.

 

actually the 400 2 stroke is stronger than a 400 ex of course,it is just a matter of time,your friend have only less than 500$ to spent on the scrambler and the few bike-lengths will be for him...

 

i know! i gotta start hoppin up the 400EX so that he wont beat me when he puts a pipe and clutch into it...sheesh...

 

Yea, the 400 Scrambler has a great engine in it. Personally, I prefer it to the 500. If only they would lighten it up some, they would really be onto something. Imagine the 400 Scrambler, with a pipe, porting, clutch kit, and 100# less weight. A little help in the suspension department, and you would have the ultimate 4x4.

Really, though, the Scramblers are good at what they were designed for. A fairly fast, comfortable go-anywhere trail bike. They are easily outclassed by bikes like your EX once you get off the trails and on any kind of track.

 

that would be an awesome 4x4