Thank you Slijkmoto for the video file showing the open top of the throttle body with the sound coming from the butterfly valve (if I'm describing things correctly). I note that the sound significantly reduces when the person puts their thumb on the valve, but not entirely disappears.
Now it gets interesting, because, at about 800 km on the clock, and for the past week or so, I am able to hear a sound relatively close to the sound in the video. I experience this sound on easy-moderate acceleration from standstill in first gear. With harder acceleration is isn't apparent, but I think that that is due to the higher general engine noise masking it. If I accelerate very gradually, it isn't apparent. The volume is what I would call low - I can't hear it with full face helmet's visor closed and I'm not wearing earplugs. Can't hear it once I'm moving with any speed at all, maybe due to the usual noise coming up from the front wheel and air passing the triple clamp, etc.
Now, it's very similar, but I can distinguish it from another, "second" sound that I hear on acceleration (any acceleration effort, low, medium, hard), which sounds very convincingly to me like the fluttering of the butterfly valves that one would more/less expect to hear on any acceleration - this sound is close in musical pitch (freq.) to the one above and which I hear in your video, but this "second" sound seems normal to me, is also (for me) pretty quiet and seems like the normal sound of the moving butterfly valve on acceleration as the engine pulls air.
What grabbed me as I listened to your video is that the sound there seems to me, to be similar to the fluttering of the butterfly valve on normal acceleration as the engine pulls air, but this sound in the video has a more metallic nature to it, more harshness, which for the past week, has been how I myself have characterised the sound that I described first above - "that sounds a little like the "normal" butterfly valve air movement sound, pitch is close if not the same, but this sound has a more metallic nature to it - maybe like two pieces of metal being rubbed together - like a pan shuddering gently against the muffler, or something like that".
So, I'm not sure if I'm hearing the same "abnormal" sound as you and Maturerider have been suffering. I can say categorically that this harsher metallic sound that I'm hearing, not dissimilar to your video, is certainly quite low and so far (fingers crossed) hasn't changed/increased, hasn't got to the high volume that the two of you have described sadly. If I accelerate gently, (pretty gently) it doesn't seem to occur, but I still always hear the gentle, airy, fluttering sound of the butterfly valves. I interpret that sound as normal.
so to close, two questions:
1) the sound that the two of you are hearing is/has become definitely loud and impossible to ignore, right? someone said it had induced tinnitus? That's what I think you both said way back.
2) am I right in describing the more normal sound that I'm hearing on acceleration to be the normal airy-fluttervalve sort of sound from the butterfly valves moving normally as the engine pulls air, normally? that is, on acceleration from standstill, is it indeed normal to hear a low volume fluttering kind of air sound? sort of a "whiffling" sound? can I attribute that sound to fluttering of the butterfly valves? do butterfly valves indeed flutter normally as air is pulled into the cylinder? or do they just open and stay fixed in place?
I can definitely distinguish these two sounds, rather related, but the one that I don't attribute to normal functioning of throttle bodies so well, seems more metallic, slightly rougher/harsher, and more like two pieces of metal being rubbed together, or like a soft sound coming from a muffler pan or similar, shuddering/vibrating when you accelerate. The butterfly valve sound that I think that I'm also hearing seems more obviously airy, it seems the obvious sound that a throttle body should make as air passed through it and through a fluttering valve . . .
thanks for reading this, guys!