First verify that your carbs are bone stock with stock needles, stock jets (all of them) and stock mixture screws. A lot of times, we end up with previous owner's attempt at "tuning". Reverting back to bone-stock often resolves all issues.
https://www.ninjette.org/forums/showthread.php?t=340561 or skip to solution here:
https://www.ninjette.org/forums/show...84#post1258484
I'm looking for Maverick9611's post where FactoryPro sending pre-gen needles in new-gen jet kit caused over a year of headaches and troubleshooting mid-range stumble. Although if your biKe refuses to rev above mid-range, it's more likely fuel-flow or clogged carb issue. Here they are, resolution in last link:
https://www.ninjette.org/forums/show...17#post1219417
https://www.ninjette.org/forums/showthread.php?t=324987
https://www.ninjette.org/forums/show...61#post1232661