one issue is the carb mount size restriction. but you can get a aftermarket case to solve that.
also can get kits, pipes, performance clutch.
then you can swap in bravo/grande/si rear wheel so you can use a variator, then get performance variator. then you can get new gears for the rear hub reduction that give you less of a reduction and thus more fastness.
read around:
http://www.mopedarmy.com/forums/discuss/read.php?f=7&i=93029&t=92821
http://www.mopedarmy.com/forums/discuss/read.php?f=7&i=92650&t=92500
http://www.mopedarmy.com/forums/discuss/read.php?f=7&i=92132&t=91803