Engine fading coming down to idle

[Ageing Rotarian]

Has anyone experienced the bike fading when hot and going down to idle?
This is something which has got progressively worse but is still a little intermittent.
Started by pulling up to a junction and then petering out, press the button engine starts and you pull away. Sometimes it will idle ok but now more often than not it fades. Had one of the club members come over to look at carb settings, we reset the main jet heights with a manometer (wasn’t far out to be fair) balanced the carbs and it all looked good with the bike idling for an extended period. Took it for a test ride first junction the bike fades.
So, thought it might be fuel tap /fuel supply, changed tanks with another Classic and no difference. Had a quick word with Graham (who always seems to have time for the club) who suggested removing the wires from the idle temperature sensor. Wires removed and the bike idles albeit at around 1400 ish rpm, bike has a minimag fitted.
Question, has anyone experienced anything similar or any problems with minimag?
I have the old Boyer system which turned out to be ok in the end and I am looking to refit it to see if it makes any difference.
As always any help would be appreciated
Regards
Roy

[fogrider]

How far down did you set the jets ? MIne is happy at 3.5mm but the factory apparently started further down on first start up. A rich tickover seems to suit mine but of course with SU's it's essentially a full range effect. ( ignoring the idle by-pass screws ). I use an air/fuel ratio meter and set it just as normal turns to the bottom of rich.
I assume the SU pistons are free in the dashpots ? and the damper oil is not too thick. I prefer 3 in 1, any thicker can affect the response when the oil is cold.

Keep at it, good luck.