I just had the kicker spring off on one of my new-to-me EC 250s and it took a pair of needle-nosed vice grips to get ahold of the spring to pull it back a bit and jam it in the hole, but it did not have to be "prewound" much, maybe an 1/8 turn or less?
Make sure you have the notch in the plastic bushing engaged on the "ear" of the spring that goes into the shaft or it will bind up when you tighten up the screws on the cover. The previous owner had this wrong and the kicker was not returning. That's why I had it apart....