Metallic clatter

[joseacayu@gmail.com]

Hi, Surely someone knows this topic. I am the happy owner of a Goldwing 1200 Interstate. I live and use it in Seville, Spain, but the bike was made in the USA, approx. in 1988.
In neutral the engine sounds normal, and in first gear you don't notice anything either. After the second gear and above 1500 rpm you can hear a cleansed metallic clatter in rhythm with the revolutions. It is perceived with quality, but the intensity of the sound is low. It stops being perceived above 2000-2500 rpm.If anyone knows the cause, I would greatly appreciate your comment.
Greetings and best luck!