So I absolutely scrutinised every single part of the carbs and could not find anything suspicious that would have caused the crappy running issue. I looked at all the jets under magnification and they all appeared clear and no unusual wear on any other parts.
The jets looked a bit more tarnished than I would have thought as it`s only been a matter of weeks since they were fitted. Anyhoo, as a belt and braces approach I cleaned every thing to surgical levels and blew every orifice through with a powerful compressor. put it all back together this aft and It`s running like a Swiss watch again. It`s still `dun me `ead in` as there was no apparent reason for the problem to start with, but I`m not going to question it too much!
The only thing I did differently was the pilot setting. When I first did them they were out 2 turns and that`s where I reset them. I had a look in the book and that says that a mk1 should be backed out 3 turns. As it was running well before, but only out two turns on the screws where the book says 3, I`ve split the difference and used 2 1/2 turns out and I`ll see how it goes at that.
Has anyone else altered the setting? how did it go? I`d be interested to know after all this bloody faff.