Cylinder not firing al low rpm

[TommyTheGun]

Back left cylinder is not firing at low rpm, but seems to kick in at higher rpm. I have recently given the carbs a good clean using generous amounts of carb cleaner. Replaced pilot screw seals and checked float heights and got new carb rubbers. Pilots screws are out 2 turns and jets are 115f 118r.
Thought maybe it was a problem with the coil but tried one off my mates nc30 and still the same even with different a different plug. The plug that was in the cylinder didnt look like it was being flooded.
Am now thinking it could be a carb balancing problem? as to get one of the pilot screws out i had to undo part of the linkage to get at it and maybe i have upset it. When the carbs were on the bike i took the filter off and had a look down the funnels ontop of the carbs and pushed the sliders up to have a quick look at the butterflies and think it looked a little more closed than the rest.
If thats not it then next its carbs off again and get them ultrasonically cleaned.