Engine vibration

[newmaac]

I rode today for the first time in several months. What a blast!!
When I last rode in the Fall, and again today, I experience a subtle engine vibration that comes-in right at 6000 rpm's.
There doesn't seem to be any lack of power at this point, and no obvious noise, just a vibe.
I have never checked the timing chain tension, and plan to do this tomorrow, but other than that, I am drawing a blank as to where to look.
It is defanitely engine, and is at 6000, regardless of what gear I am in.
Any ideas??
TIA

[MartyA]

misfire from fouled plug, weak coils, fuel starvation one cylinder, coil pickup wire...

[Geezer]

Sync the carb again.

Geezer

[buffalo]

I had the same thing last fall, only was worst between 4500 and 5500 rpm. Felt it mostly in the pegs, turned out it was a loose rear muffler mount allowing it to vibrate against the frame. It felt like my motor was ready to come unglued but just a missing bolt. Might check things like motor mounts also.