Abstract: A balancing arrangement is provided for balancing the secondary out of balance forces of four cylinder in line engines. A gearwheel carried on the crankshaft transmits drive to a further gearwheel and each of the gearwheels is arranged to drive a balancing wheel. The balancing wheels are driven in opposite directions at twice the rotational speed of the engine. Each wheel is provided with adjustment means whereby backlash in the wheels is taken up. The arrangement is of particular application to motorcycles.