Sorry....won't work. The 100mm piston is from the later DR650, it is just too big to fit into the barrel of the Savage. The DR engine has a bigger barrel and stud spacing.
The 95mm from the earlier DR650 does work....and even more better is to get that piston from Wiseco and get a jump in compression. Since you are going to have to spend money on getting the cylinder bored - you are better off buying a Wiseco than you would be to install a stock DR650 piston (unless you had one laying around).
95mm results in 666.292cc
96mm results in 680.393cc
97mm results in 694.642cc
Old post on the subject:
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1349870784/0http://suzukisavage.com/cgi-bin/YaBB.pl?num=1266928992/0