Can anyone tell me how to replace the motor on a Federal Signal model 11 that is mounted on a Visibar in classic Twin Beacon Ray set up. A parts diagram or exploded view would be helpful. I can slowly dissect the thing but I don't want to make things worse and undo the chain drive if I don't have to. I think the motor has a mounting screw on the bottom of the plate that requires me to take the light assembly apart and maybe completely off of the bar but I'm hoping it is possible to leave the chain drive cog in place on the bar at the same time. Anyone would be appreciated.