The picture you showed of your 660 choke a wee bit open.... my street avenger 770 shows the same, but the choke setting on the big dial is set to the middle, one blip of the throttle when its cold, sets the choke and off it goes to 1500rpm(holley setting), much too high IMO, so i turned the choke idle screw out 1/2 turn, slightly lower rpm now and the choke performs better for me.