My plastic choke knob came off too. Seems one of the previous 3 owners hot glued it on to the cable. Here's the best solution I came up with; it cost nothing and has kept working for 6 months. I pushed the knob up the cable, and used a propane torch to heat the last 1/8". I then took a visegrip and bent the cable end to a 90* angle. Quickly pushed the knob onto the still hot cable and let it melt itself partway into the knob. Problem solved.