careful, i've had some of my aprilia buddies looking into these and alot of the work (big bore kits) have been done by slack builders. i know from first hand experience if it wasn't done by a person knowledgeable enough the bike may be more of a headache than it's worth.
-my experience; never take your aprilia to anyone but an aprilia expert! BMW shop trashed the oil tank on mine, Yamaha shop killed my computer, repeatedly!, and Kawasaki shop damn near tore my rear Brembo's apart after not removing them before attempting a tire change!
-now i do all of my own work, the canoe from italy takes a long time to get here! only one guy rowing!
the aprilia rs-50 runs the yamaha-minerelli am-6 motor. it is a real basic two-stroke engine. a top end could be accomplished by an average mechanic in three hours, including removal and reinstallation of the motor, plastics, and hooking up/refilling the coolant. my best time is a little over two.
while i will agree that there are hacks out there that do shitty work. anyone considering one of these for the track is gonna open up the motor and take a look inside to at least check the rod to make sure the previous owner didn't drive it like a four stroke (engine brake, etc...)!
none taken, experience goes a long way on bikes! i wish there existed a knowledgeable individual in the entire state of NC that could work on my Tuono. just wanted to let everyone know that as far as the aprilia's i've ridden and worked on (no rs-50's), u take it to a "hack" and ur gonna get burned! and i'd not really consider a BMW dealership that's been around a long time to be hacks but well, even i know how to change my oil w/ out breaking the oil tube!