I'm rebuilding the pot assembly on my 520? EFM. The area in the gooseneck casting where the bushing is installed is somewhat eroded (maybe not the best word) both toward the pot and toward the ratchet. What is intact seems to be sufficient because it takes some effort to install the bushing. My problem is I'm not sure of the correct depth to install it. I want to get it in the proper location. Could someone provide me with a measurement, possibly from the flat surface on the end of the gooseneck where the coal pipe enters to the "coal" end of the bushing. I hope I've made this understandable. Thanks in advance for any help.