Any advice?I have a UK model XJR 1200 that is makeing a tapping sound that sounds like a pencil being tapped on a table.I have checked and replaced two shims allready and carbs are balanced.Mileage is 22000km/13021 miles.When i bought the bike few months before the noise was not there.The bike is stock standard except for K&N airfilter.All valve clearances is correct any ideas out there please?