Before you do anything else, change the battery. It is knackered. At this point tell us if you still have any issues with the electrics. Indicators and brake lights use power from the battery, which you don't have. Don't mess with anything else electrical until you do that. As for the tapping, the first thing is to check the tappets. There are exhaust and inlet tappets on the bike and these are easy to get to and adjust. Use the search facility on the forum as the method and measurement of these have been posted many times. Both the battery change and tappet adjustment are very easy jobs. Once these are done, and if there is not difference, then things get a little harder. You should be able to change the battery and adjust the tappets in less that 2 hours with limited mechanical knowledge. About 15 minutes once you are familiar with the bike.