Z1OwnersClub GB

Well now I have finished my KZ550, I have managed to have a few run outs, one problem I have found, when the engine is hot, say 5miles, the carbs hang between gear changes at about 3000 rpm, will fall back when pulling to a stop, will hang again sometimes, not all the time, again when I tweek the throttle, have done the usual checks for air leaks, wd40 method, all seems ok, baffled .

Typical head to carb rubbers air leak,are the rubbers new? sometimes they distort against the head or are hard and dont give good seal, could be opening up when get hot...