2021 Kawasaki zx10r Gen 6

16/38 is good; factory is 17/39 if I recall; that has the top end. 16/39 might work best; steel for both on this bike.

if you are gonna drop one in front dont drop rear too, every 1 up front is 3 in rear. but backwards. so drop front up rear 3 same shit. usually its -1 +1 or -1+2 cause -1+3 is the same as -2 follow. you lose top end every tooth up front you go down or in back you go up but gain acceleration, gas mileage goes to hell as well other way around you lose torque and gain some top end to a point. geared right and ecu flash you can break 200 but it will be a dog in comparison to dropping a tooth up front and if you go up 2 rear it kinda becomes a pogo stick, power wheelies for days lol