That is plain and simple assault and you need to file a police report. I also think you need to make you bike tamper proof like a locking gas cap and hide as much wiring as possible. A few years ago I would have told you to wait for him on a dark night and pound his nose thru the back side of his head but I have learned a few things over the years and you will fair better just having the police handle it for you. I bet this a-holes parents wouldn't think his actions were proper and hopefully that will end it. Beyond all of that get your bike fixed and keep riding it! You need to remember some people are just asses and no amount of beatings or law suits will change them. Keep rollin!