You should not need a damper. You need to make sure your rim is true, your tires are in good shape and properly inflated, your forks are working properly, and your headset is correctly adjusted.
In my opinion a steering damper on a stock, non-racing SOHC4 is an affectation. If you like the look by all means add one, on a cafe it can really add to the appearance, but it shouldn't be necessary for good handling at normal speeds.