In cold weather, air is more dense and has a higher volume, thus, more oxygen per area, equals the one click starting. In hot weather, "you have to give it some gas to start", or "I had to stay on the throttle half a turn" actually, what happened here is you opened up the throttle plate, thus, air passed in and it started. It's an air issue and nothing more. So, try this, stay on the throttle (don't pump gas unless you have to, just twist to open the throttle) then start the scoot. You can try opening the throttle more than half turn, but don't pump. Works for me everytime.