The easiest way to make adjustments on your Hunter rotor is to use a Hunter adjustment wrench. This tool can be purchased from your local distributor.
There are two adjustments that can be made on your rotor, the arc and the radius. The arc adjustment is responsible for changing the rotational pattern the head is going to cover. The factory setting and minimum arc on a Hunter rotor is 40 degrees (50 degrees for PGP-Ultra and I-20), the maximum is a full 360 degrees.