Some progress...
Took the carb off the car this evening, was easy enough to remove - the spare carb is seized to its inlet manifold, I was glad the one on the car just unbolted.
I took the carb to bits and used a lot of carb cleaner to get it as clean as possible- the diaphragm is in perfect condition, it might have been replaced recentlyish as it feels soft and supple. The needle has a tiny, just visible to the eye, mark down near the tip, a horizontal scratch around maybe 1/5 of the circumference. Hard to see, I can feel it with a finger nail though. I guess a replacement needle would be a good idea. The air valve on the side was seized and gummy, even after cleaning it with cleaner it didn’t operate like the one on the spare carb so I swapped them over.
The adjustment bolt on the bottom had another 1 and 1/4 turns in to go, so there’s some adjustment yet.
I’ll get it back on tomorrow and see how I get on- I’ve booked half an hour of workshop time before the mot so I can have a play with the car hooked up to the emissions monitor. If needs be I can use that time to remove the airfilter - thanks for the suggestion
Cheers
Oh, the needle in the spare carb is definitely bent- it looks bent and as it’s spring loaded I can twist it in my fingers I can feel the bend. I’ll post a photo when I get a chance.