Was just talking to a guy about a CBR250RR and he said the carbs probably needed sinking, what exactly does that mean needs doing to them? What problems will the bike be having without that being done?
I agree with Eric, and what it means Ratty, is to make sure each of the carbs is pulling air/fuel through at the same rate/pressure. There is only one way to do it - with a vacuum measuring device of some sort. There are however, many vacuum measuring devices - gauges, steel balls in tubes, and wine bottles..
The end result is both cylinders producing the exact same amount of power, or near enough and avoids one running rich, and the other lean, and screwing things up.