We’ve previously written about derestrictors you can buy ready made for various motorcycles, primarily the big Suzukis and Kawasaki ZX-12r. If you can solder and use a multimeter and have basic electronic knowledge, you can build your own ZX-12R derestrictor. The author has schematics and photos on his site and it looks very straight forward, one transistor and a couple of resistors are all that’s needed. Just remember to be careful if you plan to test your handiwork.
The Kneeslider: Kawasaki Ninja Motorcycles for sale