crackle and pop

[martync]

The old XT is playing up again, there seems to be a carbouration problem. It seems as if the carb is moving in time to the engine (back and forth) and thus the manifold is loose. It runs OK at high revs but when left to tick over it seems to every 30 seconds or so explode or pop.
it sounds as if air is being pushed back to the carb, its only on the right side (secondary carb). could an air leak from the loose manifold do this?

Ive tried tightening but it seems to be knackered however I don't want to replace it if it's not the problem. again other than that it goes fine but may get hot if I leave the choke out at lights (to keep it ticking over at 2500 rpm)

any thoughts appreciated