When I flew the spin testing on the MXP740 Savannah with a Jabiru 2.2L engine, the engine generally stopped at about 2 turns. It was never considered appropriate to give it a deliberate spinning clearance anyhow, so that was no big deal - but it did show the wisdom of the teaching that you always do such testing over a runway! (Although, as for your Robin, it also restarted easily enough.)
G