1969 SIIa 88 2.25 petrol

I worked on resolving my inconsistent idle issues today - because idling had become non-existent since yesterday - it would stall without choke. Change in behavior happened suddenly so I suspected dirt.

So first I did a general tuneup - valves, plugs, cap, rotor, points, fuel filter and then after fiddling with the idle mixture and speed screws at first I thought I had it fixed but then it did the same thing again, so off came the tire and bonnet and up to my elbows in hot engine I went - again.

This time I removed the idle jet and blew it out - seemed to do the trick.

Question - what is the electrical thingamabob on the idle jet? there's a wire that goes from my coil to the end of this small canister that the jet screws into - some kind of diaphragm in the thingy controls the needle.

Does anyone know the purpose of this thing?

mike