Slight buzz or vibration at 5000-5500 rpm

I was just wondering if a buzz or slight vibration at 5000-5500 rpm in all gears was normal for a KZ550. My new Yamaha buzzes at certain RPMs but not quite as bad. There are no rubber grommets as part of the engine to frame mounting on the KZ550. I'm wodering if this much ado about nothing but wanted to see what others experience since this is my first bike of this age. Other than that, the bike pulls hard for an old bike. I've only done a bench sync on the carbs but it runs fantastic so I'm reluctant to tinker with it any further. Am wondering if syncing the carbs would help or if I should just shut up and ride it.

My 750 twin always had vibration in the 3500 - 4000 range and it has gotten gradually worse with age. I suppose the balancer chain/bearings are wearing. Not sure about a 550, but they all will buzz a little bit.

My 650 buzzes at 5-6000rpm. There have been many discussions here on blurry mirrors at freeway speeds!

Yes, my mirrors get blurry at highway speeds also. As soon as the rain clears, I'm hooking up the manometer in hopes that a sync might help some.

my 1000, does this also, I installed the bar dampners, helped a lot, I have checked the timing and moved it around some, this seemed to help also

All rotating devices have what's called a "critical speed"
where vibration cannot be avoided. It can be reduced with careful balancing and/or counterweights and/or balance shafts....but never completely eliminated. Maybe a physics major who is more familiar with rotating masses can chime in and provide more detailed info.

I figured out the vibration problem. 2 out of the 3 bolts which hold a triange engine mount bracket were loose. I'd read this on another post and decided to check it out thinking that there was no way any mounts could be loose. Vibrations are dramatically reduced.

I was pretty happy to find the issue at first and then it became a little frightening to know I had the bike running at highway speeds sometimes with the engine not mounted totally secure.

It's a great lesson learned. Looking back, the fact that it started becoming progressively worse should've clued me in to the source of the problem.

Use some #242 blue loctite on the bolts. It's the non permant type like the #222 red is.