Part of the post 100 hour service test flight on the UH1 was to move the cyclic forward and right to aft and left in three seconds, and vice versa to check for any propensity for jack stall. This exercised only one jack at a time. The observer used to cover the hydraulic boost switch, to turn it off and then on if a stall occured!!
You could induce it fairly well by pulling up and rolling from a high speed pass!