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With regard to the diagram on the page referenced below, can you identify for me, what part you call the 'Roller Arm Wheel' ? I know that the parts diagram is very complicated on this model and type of machine, and I know where the Roller Arm is, but what is the 'wheel' in question ?
It looks to me as if the wheel has a bearing in its center. If so, and if it doesn't fit over the old bearing in-place, you would have to remove the bearing also.