No exact answer and results vary like climate , altitude , exhaust and if you modded the airbox or installed a Uni or K&N . I used a 95 MJ with my 50mm BBK since I live near mountains and its so darn humid .
I would get a jet kit instead of paying per jet price . PFS has one but their site seems to be down at the moment . Here is another source for a jet kit
http://enviromoto.ecrater.com/p/4129...jet-set-gy6-50