The spring is suppose to keep the screw from vibrating out.

Hey Derick, I was inspired by your video's and pulled Shirley out of the garage and fire her up (3 primer kicks, 1 kick to ignite!) and after she warmed up, my idle was starting to race like yours. Its cooler out than the last time I had it running. I turned the air screw a 1/2 turn "in" to richen up the mixture and the idle settled down and sounded good.

Post another video if you can get your Zilla in line with that idle.