I have a Nelson Beta II impulse (pulsating) sprinkler that has worked fine until this spring. Now, it will turn to the right (clockwise), but when it reaches the end of the range, it starts pulsating faster (as they do when starting the return rotation), but doesn't move counter-clockwise.
As long as you haven't lost pressure in that zone for whatever reason try this. Totally saturate the head (everything that moves)with silicone spray and work it back and forth by hand then test it out. This trick has always worked well for me and I have heads that are 20 years plus old. Won't hurt to try right?