missing at idle

My bike is missing and back firing at idle and low revs also when throttling off it is back firing seems to run fine 2500 revs and over any ideas where I should look first? burning a nice pipe after a run. only missing on one side,if I had long enough plug leads can I run left plug on right coils? as they both fire at the same time as I understand is this correct,if so this should rule out electrics shouldn't it? Have twin amals and not smoking, plugs no sign of oil, exhausts burning as clean as you could expect with modern fuel

If you have two carbs after checking out spark issues you may need a clean out of all internal passages of bad side..
If one carb then ignition.
If two carbs I'd check out electrical before I go into the one on the bad side.
Before I mess with coils I'd swap plugs to see if bad plug. Also see if plug from bad side shows oiliness, although you don't mention smoke.
If oily you may have failed intake valve seal or worn rings or worse.
If no change with plug swap I'd start to wonder if a coil is breaking down.
Swapping wires since you have a wasted spark ignition I suppose would serve as a test, but maybe just swapping them over easy enough.
Possible failing spark plug wire so just swapping them around worth doing.

That's pretty much my best guesses.

Exhaust air leak ? possable .

Know which side? Mine will do this every so often on the left side only. Cleaning the pilot jet with a #78 drill fixes things right up.
FWIW :|

plug leads were long enough to fit on other side ,tried but still missing on same side (left) so will take off carb now and clean out

Solved
Took off carb from offending side stripped it and found fuel bowl gasket has a piece missing around pilot intakes replaced now runs like a dream thanks for your help Norton forever