How do you shift into the second tier of gears On a 1981 Honda CB900C motorcycle?

Answer

On the 81 CB900 the low side is for faster accelerations or for riding in the mountains or in town. thehigh side is for highway riding and helps improve fuel mileage.

There is a lever which selects which set of five gears you are using. You can change from one mode to the other as conditions warrant.