the balancer shafts are the internal engine equivalents of an external harmonic balancer that is used on the crankshaft of most domestic engines. Honda uses 2 balancer shafts (front and rear) on the 4 cylinder accord engine.The balancer shafts dampen engine vibrations due to the recipricating motions of the piston and crankshaft by keeping the engine "in balance". it does this by creating an equal and opposite force to counter-balance the recipricating motion of the crankshaft. The result is a smoother idle and less vibration transmitted to the interior of the car.the shafts have to be aligned when the balancer belt is changed. the front balancer shaft is aligned to the oil pump housing and the rear shaft to the engine block markings. if the shafts are not aligned they will not be in sync with the crankshaft motion. They won't go out of sync if you change that belt first without disturbing the engine position by rotating teh crankshaft with the belt off.There are several manufacturers that use balancer shafts under different names. Mitsubishi's is called a "silent shaft". The balancer shafts are more popular on imports than on domestic cars.hope that answers your question