[ausev] Souping up a small dc motor

[evehicle4me at hischopsticks.org]

I just bought a Dahon folding bike.  I really enjoy riding it but  
already am thinking of ways to add a small motor to the bike.  There  
is a space within the frame that will accommodate a motor that I have  
found but it is only 24 volts/200+ watts.  Is it possible to rebuild  
this motor so that I can run 48 volts through it (and still get a  
typical service life out of it)?  The motor will drive the rear wheel  
through a chain.  I know I will need a different controller for it but  
controllers for 48 volt motors are pretty easy to find.

I am hoping to get at least 500 watts into that space - 600 or 700  
would be idea.  yes...I know, if it had wings it would fly :)