Abstract: An improved hydrocyclone and method of operating for centrifugal cleaning of pulp for papermaking wherein the hydrocyclone has a plurality of inserts each with openings of different sizes for selectively and interchangeably inserting into a stock entry opening and into a vortex finding outlet opening to adjust capacity and cleaning efficiency. In one form the inserts each can be changed by tubes of different openings which are installed into the inserts changing the opening sizes. In another form, the inserts are threadedly engaged with bosses or are adhered or frictionally fit into the bosses.