I have had the chain loosening problem before. It is at the point the chain is wore out, the O rings are prob. shot and it wont hold much lube anymore. Chain even looks a bit rust coloured after riding. Being so worn it heats up and stretches easy. Use of a chain wax instead of one that flies off helps. The noice is not only due to the chain hitting the swing arm but also that the links are now too long to fit properly into the teeth, you also must have some links that are starting to stick, you will see this by watching your chain as you turn the rear wheel. They go by kinked. On a trip I was tightening twice a day until I replaced it. Sprockets only need replacing if they are starting to hook, or the ends are starting to become pointed as compared to flat blunt ends. I have 60000k on mine and it has been driven hard. I replaced the stock chain at 23000k, second chain at 40600k. Rear sprocket is still stock and I replaced the front at 44000k just to drop to 16teeth. (much better in the corners!!!) Hope this helps.