I have a 401A and have taken it apart for a good "spa treatment' including the cam stack. The different references are great for cleaning. My friend was given one that sat in a barn for years in its cabinet. Her husband removed the machine and between the three of us we got it cleaned and running like a new machine. husband had some grease solvent to remove the hardened grease. After ordering a couple replacement parts it now sews and sounds no louder than a sleepy kitten. She still uses it and I believe more than her new one. The cabinet itself was not salvageable but the hardware was including the lift for the machine and the knee pedal. He just made a new cabinet for her out of an old executive size desk. Stunning. Cost total was maybe $100. It was a labor of love and to think it was one of their granddaughters who saw it. they were about to tear the barn down.