How fast can you make em all depends on how much you want to spend like everything else.A good running 400 with race porting and a pipe,carb and the right clutching will give a stage three DS just about all it can handle.I agree with what you said about the 500,there just isn't that much in the way of mods to get it where the 400 can go.Good luck with your decision.

 

chadscrambler,
If you want to get crazy with a 400 xplorer check the "Beast" out on my photo page. http://home.bellsouth.net/p/s/commun...groupid=172623 it's a mod. 95 xplorer 400, was a 4x4 but i removed it since i never used it. Last week i bored it 80 over ( was 40 over) and increased the amount of port/polish that it had , still not to race porting.
hunt

 

Ive seen 400 engines make damn near 100...the best one I found on a drag bike was about 93 HP with no nos or turbo...youd need a 720 kit and turbo to make that much....it may be a polaris but they sure will haul a$$..... [img]i/expressions/face-icon-small-happy.gif[/img]