I attempted to pull it out and the screw was so tight that I stripped the head. Despite the tightness of the screw the arrestor slides in and out about 1/4" as if in an elongated hole. The result is not only vibration but a loud muffler. I need to get a screw extractor and hopefully when I pull it out it will solve the mystery. I ended up jury rigging it with tie-wire and the thought comes to mind of the old saying: "there is nothing so permanent as a temporary solution" Anyone had it off that can offer a likely explanation? BTW, the bike is a 2013 and kept in the garage so I wouldn't expect the screw to be rusted in there.