If what you are calling a miss actually sound more like a mild backfire shooting out one of the carburetor throats, that's caused by a lean running carburetor slow speed jet, located near the rear gasket of the carburetor just above the float chamber gasket (In back of that silver looking aluminum screw plug), one for each cylinder. That jet is a FUEL jet NOT a idle air jet and should be numbered (imprinted on its face) number 48C (.048).
Have the engine idling with the problem occurring, Stick two fingers into the carburetor throats, one by one. When the engine smooths out, you've found the offending carburetor.
Should this be your problem, clean the jet and try again. If the problem persists, you can drill the jet a one thousands larger or so at a time (whatever it takes... trial and error) until you obtain the proper idle mixture.