Abstract: An adjustable brush for cleaning sprocket chains, particularly on motorcycles, has a three-sided adjustable rectangular cleaning channel, one wall of which is adjustable manually during use inwardly and outwardly to change the width of the cleaning channel while maintaining the rectangular configuration of said channel. The brush allows effective cleaning on three sides of a sprocket chain simultaneously. Various improvements are possible including the use of rollers to facilitate smooth movement of the brush surfaces over the sprocket chain, the use of a transversely movable or adjustable intermediate brush at the head of the cleaning channel and the use of a closed four-sided cleaning channel.