If the bottom of the main nozzle doesn't touch the top of the bowl nut, it seems like the nozzle would have to be pressed in or it would not be positively located. That also lines up with the instructions only referring to it being removable on the Series 7 (yours is Series 3/4). So, the next trick is to get as much gum out as you can, then try it. Did any crud come out the last time you blasted it with the discharge nozzle blocked? When you do that, is crud coming out of the main air bleed, close to the throttle plate? If you can squirt cleaner in the bottom of the main nozzle and have it come out of the main air bleed, I think it has to be going through the radial holes to get there.
