sounds lean. I would first check the fuel filter. if that doesnt help check the idle mixture.
When yamaha drills the holes in the tanks they don't clean them out too well. I've has a couple of 660's pop cause of that reason.
2006 660 SE, So Cal Fab long travel, King dual rates F-R, Team IMS racing 686, Ported Head and 1mm oversized valves, IMS performance cam, Mikuni HRS45,FMF dual exhaust, Dunner Clutch, CVT filter, K&N air filter, outer wears, Gorilla Axles, BFG's on type 7, Big horns on Spiders, Stockers, Mud gears on rockstars, two hella lights, alpine deck w/ two 6x9's, Homes made two seat cage with door panels, four point Crows and Winch w/rope.
2007 Silver SE four seater for the wife.