The large majority of the sprinkler heads we install at Jensen Sprinkler are the Rain Bird© 5000 rotors and the Rain Bird© 3500 Rotors. The nice part about these two rotors is that they adjust in the same way and all you need is a small flat head screwdriver to make the adjustments. 

In this article we will look at the radius or the throw of the rotor. If you are looking at adjusting the arc, or the side to side sweep of the head, click here. 

The radius adjustment screw is found on the top of the sprinkler head on the side nearest the nozzle where the water sprays out. If you are trying to find it without the sprinkler on, the screw is inside the raised arrow printed on top of the head that points in the direction of the spray. The screw is enclosed in kind of a rubber bulb so it isn't readily identified as a screw, but it is safely tucked inside there. Slide your small screwdriver into the opening in that raised bulb and fit it into the slot. Turn the screw counter clockwise to increase the throw and clockwise to decrease the throw. This is best done with the sprinkler running. 

Here is a short video from Rain Bird© that may be helpful to you: