aileen,
Somewhere on here I have posted annotated pics of where to oil and grease 401s. I forgot to bookmark it so I can't find it. But it's in here somewhere if you can scare it up.
Also here is the Singer site for owners manuals. Just key in 401 and you can get a free download. I suggest you save it to your hard drive and print it out so you can take it with you to your machine. Everything you need to know about the 401 is in the manual.
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http://www.singerco.com/accessories/instruction-manuals }
One of the best cleaners I've found for the later Singers is denatured alcohol, q-tips and cotton balls. I just did a 500 with that combo.
Then after I had it working my wife took it away from me ....
This design of Singer machines are oil hogs. Lots of moving parts that need oil. I suggest Tri-Flow oil and grease. It does make a difference.
Joe