Depends, CB500 or CB550? For a CB500 it is real simple. Final drive ratio is 2,0. In 5
th gear:
80 km/h = 4000 rpm,
100 km/h = 5000 rpm,
120 km/h = 6000 rpm,
140 km/h = 7000 rpm,
160 km/h = 8000 rpm.
Don't you love the decimal system?

For a CB550 it's different and the CB550K3 on the European continent is different to the K3 in other markets as it had a 34T rear sprocket where other models had 37T.