Thanks blackriverfish. I agree, it does not look as if that used to have a screwdriver slot. It still has an entry radius and I can't imagine the previous tenant having reproduced one of those, and polished the thing, if he/she had just finished ripping the screwdriver slot off it due to overenthusiasm.

You seem to now have a couple of options. The one I'd consider first, is trying to pull the whole main nozzle out of the carburetor. I'd try cleaning it up thoroughly to get the gum off, then use a short piece of steel tubing, with a longitudinal split down the outside, pushed over the outside of the bottom end of the main nozzle. Use a clamp around the outside of the tube to tighten it onto the main nozzle, then pull and/or twist the tube.

If you conclude that this will not work, you have a crude-fix option available. If you blast carburetor cleaner into the hole in the base of the main nozzle (using the long thin extension tube that comes with the can of cleaner), giving say three half-second bursts, you will probably clean out the whole length of the tube, and the main discharge orifice at the other end of it. What you probably won't do though, is open up the air ports near the bottom that make it an emulsifier - see red circle on diagram:

[Linked Image]

However it may be just about possible to clear them by putting your finger over the main discharge orifice (finger in the venturi of the carburetor) while you do the carb cleaner blasting, hoping that the plugs of gum in the radial holes will be pushed out and dissolved.