I considered the fact that he is able to go 75 mph when I made my recommendations. It is possible that when a bike sits that gas can get between the slides and bores the slides travel in and the slides can get stuck but if he is able to go 75 mph, the slides are not stuck... more likely holed. I WOULD NOT muck around with the carburetors prior to performing OTHER tune up steps... valves, cam chain, timing, etc. If the carbs are gone into and you mess them up and your problem is with the basic state of tune of the bike, then you have a bike that isn't tuned with mucked up carburetors. In addition, I would pay close attention to fluids, cables, brake pads, etc as well... these issues are often forgotten in the urge to ride.
wiredgeorge Motorcycle Carburetors
Mico TX
www.wgcarbs.com
Too many bikes to list!