I stopped worrying about rattling bike engines a long time ago. There´s a lot going on inside that casing and things like cam chain tensioners and valves, especially at tickover, can sound frighteningly noisy. If its quiet and smooth under power I wouldn´t worry! The carb synchronising is a good idea. Also an octane improver. At 10.something to 1 thats a high compression ratio and 95 octane just doesn´t do it! It needs to be about 98 octane or higher. The retarded ignition at tickover often causes knocking and uneven running with low octane fuel!