its the circlular spring, it returns the kickstart assembly, so you can kick it again. it fits into the hole in the case, not the cover. there is a picture someone took and points out where the three parts of the kickstarter goes. you have to take the footrest off, cover off, and then line up the square piece on kickstart assembly, and the circle spring, and then the flat spring gets twisted and pushed into the correct hole. search kickstart on here and find the picture diagram, its color coded