I don't know what would be causing that grove. Is the screw tight on the choke plate? when you open the choke can you move the choke plate If you can then your screw is loose I would take the screw out making sure the plate stays the same and use lock tight on the screw, As far as my choke I have A servo mounted and I use A ball and socket on the choke arm I use it to choke the engine to start and kill the engine if something goes wrong. I use channel 5 on my radio and adjust the end point to set the throw I will try and get A picture of my set up In fact let me take A picture of the one I am working on now Its A dle 30 but should get the idea its a rear carb