exhaust bangs on over-run are usually due to poor combustion, ie too rich (caused by hitting the kill switch) or too lean (variety of causes, ie holes in inlet/exhaust that you are aware of. Try richening the idle mixture, There should be a pilot mixture control for the idle setting, richen it up a little, to see if that helps. on the zrx1100, there is a enrichening device deliberately to prevent over-run backfires. the bigger the cylinder capacity, the more of a problem this is for bike design engineers.
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