The crankshaft with mass balancing of second order in a four-cylinder reciprocating-piston engine has one or two bevel gears which are formed from the crank web and crank and drive one or two pairs of output bevel gears on rotary pistons at twice the rotational speed and at 90 degrees angle of crossing. A balance weight is fastened in a rotationally locked manner to each of the pivot pins. <IMAGE>
