Continued to try and diagnose the carby faults.
First I removed the pilot air screws, got a syringe full of fuel, and squirted it as hard as I could through the pilot-screw holes. I then followed this up with more compressed-air. Put it through the carb-tune steps, and found that it idles mainly as a single, on RH pot (LH one “chimes in” occasionally). Yet both pots will run singly, without the other one. LH pot can have pilot-screw taken out completely, and it still runs by itself. RH pot runs best with screw at ½ turn out.
I next tried to do something about the heavy throttle action, in case this was implicated. Took the throttle cables off altogether and oiled them. Found a kink in one portion of cable inner, which would contribute to a heavy action. Did my best to straighten the kink, but really the cable needs replacement, it has seen better days.
While doing all of this, I noticed that the slide is sticking open in the LH carb. Backed off the inlet-stub nut by ½ a turn, and it immediately freed the slide again. Have to be real careful with over-tightening these carbs! It is such a fine line between too-tight and too-loose.
Tried carb tuning again. Now RH pot idles fastest with air screw completely seated, while LH carb does not respond to screw position at all!
I took off both carbs again, and left them for one week soaking completely immersed in petrol.
