Could be resonance. Generally every bike has a spot where there is more vibration than the rest. It can vary based on exhaust, intake, and other mods. My truck has a higher vibration too at like 2200-2500 rpm.

 

That would make sense, I just don't think I noticed it on my previous 400.

 

Where do you feel the vibrations? If it's in the handlebars get some weighted bar ends. Be sure to check everything is tight (engine mounts and everything else)

 

nah, its a butt feeling ... lol , can feel it underneath me.

 

Vibes on many bikes in high rpms is normal. Though I don't know how smooth the typical Ninja 400 is. But my 650 and Speed Triple both vibe more in the upper rpms. Manufs have to make a trade-off between vibes / more power / quicker revving, versus more counter-weight in the engine and power loss for smoothness. Harleys literally have an engineered amount of signature vibrations that specifically change from idle to cruising.