Has anybody experimented with changing reeds in their 400? I need more power. A friend has a 700 and he's right much faster. What about a pipe? Anybody sell a better one than stock?

 

reeds don't do much. pipe, porting increase in compression.
700 what? what year xplorer?

 

you can look into different gearing for it ,but there is no substitute for cubes.

 

A good pipe made from a company that specializes in Polaris 2strokes with matched clutching for that pipe.A good set of reeds and properly jetted and you will run with a 700-800. Add a good trail port and you will smoke them.
As for the statement of "you can look into different gearing for it ,but there is no substitute for cubes." Dont listen to that on these 400 2strokers.First NEVER bore out any more than you have to and with the 4x4 system on these regearing can cause major head aches