works is basically the same as factory backed. works bikes get prototype parts not available to the public and lots of factory backing$$$$$$$$. a factory or works bike may look like the bike you can go buy but could have a one off crank, one off pipe, etc, etc. so someone riding a factory sponsored bike could consider that bike a works bike. a works replica is just a replica of the factory bike so it probably just has the sticker kit the factor pro is running on his works bike. back in the day the 2t works bike always had different pipes and we now call them works pipes the ones that are all cone sections welded together. this is just what we call them because of there looks, the old factory guys had this look because they where constantly changing the design of the pipe. all in all describing a works bike is hard but basically a works bike is a factor sponsored or backed bike with parts not available to the public.