81 lc miss on idle?

[muddyfox]

hi chaps got a mot booked for friday so i thought id get my finger out and sort the bike,

on idle is sort of goes brr,ding ding, ding ding, brr, almost like a miss, left jug if your sitting on the bike, tried a br8 plug just to see if it the plug, still does it but not as bad, seems to rev really nice when warmed
does spit a bit ofblack smells like fuel when reved out of both spannies, right jug is very happy
bog stock 4lo
31k carbs
reed spacers
allspeed pipes
float hight is good 21mm or so
240 mains
27.5 idle
1.25 air screw,

any ideas

[4l04ever]

I would strip the carbs and check everything is clean. Pilot jets could have some blockage. Check the emulsion tube is clean and also check under the needle valve seat is clean.