i had a similar problem with my old dr, and i'm not saying that is your problem, but just here to give you an idea. i had just fininshed rebuilding my motor, this was like the second ride. I just can off a trail and decided to shut her off to talk with friends, then went to kick her over and she was locked up, but before it locked up it made a wierd clicking sound like the one you described, i come to find out that a cam retaining clip had broken, and floated through the bottom end and lodged itself between the stater and flywheel.
But in your case, forget about the decompression release and check the valves!!!!!