zxr250 stalls idle just drops

hi im having problems with my zxr250 bike runs well but when i stop idle starts to drop i have to up the idle when i stop then drop it when im moving. Carbs have been balanced and bike serviced but i got it back with many issue that have slowly been fixed leaving me with 1 last headache. The guy who worked on it is no help hope some1 here can be. pleaz