Ok if it is the roller bearing or any other bearing the easiest way to clean them if they don't have a plastic shield is to heat them with a lighter and soak in a shot glass with a 1/2 inch of WD-40. Then dry off and oil well with a good oil like quantum hot sauce if not 3 in one works great. Next place on a pencil (sharpened side) and spin with your finger on it bearing should feel smooth if not repeat procedure if bearing is still rough replace as balls are rusted.