Nag, nag, nag.
You're in luck, because it turned out that it got up to about 65°F today -- we're still below freezing at night -- and we haven't had any significant snow for a few weeks, and the town has salted or brined the road in a month or so, and we've had some rain to wash away the dust and crud.
So I went for my first C 400 GT ride in three and a half months.
And in addition to my normal ride recording via my windshield-mounted camera, I added a chest-strap-mounted one, just for you, for the start of the ride. And quite easily duplicated your situation on my '23 C 400 GT. As I mentioned earlier, this is the same situation that I noticed early on, doing some double-arm, criss-cross, stretching, shortly after I started riding my (former) '22 C 400 GT.
Only this time I documented it:
Yep, same as you: c. 37 mph / 60 kph, both times. My '23 C 400 GT had 439 miles on it when I filmed this, and had its initial service at my local BMW dealership back in December (after which it just sat in the garage, until today).
(By the way, if you go to the video on YouTube itself, I have a fairly long write-up in the Description field there. Click "More.")
I'm not an engineer, or even a trained bike mechanic, but
I still maintain that:
- I've experienced this
hands-off handlebar shake on, I think, every bike I've owned, from baggers to scooters. Go searching through assorted bike forums and you're bound to find discussions on this.
- This is
not a high-speed wobble, tank-slapper, head-shake type of situation, because you have to purposely take your hands off. And you have to look for it, e.g., slowly coasting down at the right speed for a given bike.
- So this is a normal situation for a bike ... again, if you look for it this way .. and so does
not represent some improper adjustment of steering-head bearings. I'm sure that many bikes out there are in need of steering-head-bearing adjustment -- it's an eventual wear-item maintenance task, just like replacing, or repacking, or tightening swing-arm bearings or wheel bearings -- and I also assume that misadjusted or worn-out steering-head bearing can cause all sorts of problems. But what we're talking about here is a hands-off phenomenon of brand new bikes, not a case of hands-on steering with worn-out stuff.
And Mike -- you're reading this, too, right? -- have you given this a shot? As you can see from my video, it's not that hard to duplicate.