On my 2021 GS something strange happened last week.
I have this noise sice the first year of ownership. I noticed it's more pronounced on hot weather then on cold and I know exactly how to make it show up. On idle, quick blip on throtle (full twist) and letting it go back (all very quick), after the grip goes back all the way, I can hear something "jumping" inside the engine. It's metallic noise, like I have loose screw jumping arround the not lubricated part of the engine. That's one way.
The other way to provoke it, is riding steadily at 2000-2200 rpm and then abruptly open full throttle and let it accelerate. I can hear "click, clong, click..." metallic noise during 3-4 seconds and then it would quiet down. I could repeat this all day long and the noise would always be the same.
Last week, I lost my patience. This noise is so disturbing that I'm fed up of my bike. It has 20.000 miles now. I've spent so much money on it and it sounds like a piece of junk. So, I brought it down to 2000 rpm in 6th and then fully open the throttle, let it make noise then closed the throttle. I repeated the proces 10-15 times very quickly and violently, like I wanted something to brake down inside the engine.
Well, each time I've done it, noise got a bit different. At the end, like 15th time, the noise has disappeared.
Did I brake something? I don't kow but the noise has never returned.
Just as a side note: I've done this very, very violently, out of anger, full of rage. If I was just a little careful, maybe it wouldn't give the result I achieved.
Let's see in coming days.