Ok, so bike started ok in the morning. Cold so i tried some choke, same result: revs dropped below 1k. Performed regular warm up procedure wit no choke. Once warm, revs were jumping from 1k to 2k, gave her a bleep revs dropped to 1.25k then jumping started all over again. Revs really rough but no stall so off to work.

On the way home I tried what i thought was a plug chop: high revs up a hill then hit the kill switch.looked at the plugs and they were a tan colour = lean, but i have the air screws set at 1.5 turns as per stock set up??????? day temp was about 15degrees. Maybe an air leak somewhere? took the air box off and the filter the mechanics made was really rough, with gaps around the edges in some places, but the box itself has a good seal. carbs and box seem to both be seated correctly..... Started her and the same rev jumping was going on.......

Only other thing to note was the front cylinder: at idle it was 'off beat' compared to the top. with a little throttle both seemed to 'pop' in time.

On both carbs: main jet = 128, Jet to the left = 38........

Frustratingly intrigued!!!!!
Please help, Gods of NSR knowledge!!!!!