If it's only the threads on the screw itself that are damaged and not the threads that the screw goes into that are damaged, you can replace the screw and the engine is fine. If the threads where the screw goes in are damaged (which is likely, as I can't think of a scenario in which both would not become damaged at the same time), then there is nothing you can do. The engine is shot if that gear can not hold itself in place. But there is good news. You can buy the replacement screw (I'm not sure where, I haven't looked for two stroke parts in well over a year as I drive a four stroke now), and put it in, if it stays in you're golden. If it doesn't, you need a new engine. As far as the whole wife situation, all I can say is good luck. I already had a bike when my wife and I met. She didn't like it that much either at first, but I explained it like this. No one is perfectly safe from idiot drivers, but the more I ride, the more experience I will get, and the more aware of my surroundings I will become. I pay as much attention on the road as I can, and so far I've been paying enough attention to avoid every idiot who has threatened my safety. The possibility is there that one day I won't be so lucky, but until then I have to get back and forth somehow (I don't have a license) so let me make use of this cheap form of alternative transportation and enjoy it while I can. I wear a helmet and that's the best thing I can do to protect myself. She accepted that explanation and that settled that discussion. Honestly if your wife is that uncomfortable with it, you may want to think about giving up now, because she won't be happy until she makes you give it up, and then you'll resent her for it. I speak from experience, not specifically with motorized bikes and relationships, but with other things.
