bkay

I had a similar problem with my 401. A deep cleaning of the bobbin area solved the problem.
bkay

Rocketeer

I tried multiple different bobbin cases, bobbins, threads, cleaning, oiling, etc. I was almost ready to get rid of the machine. The problem seemed to come and go, but lately it was constant....

Mickey2

Is that a replacement part? These models were so tried and tested, there should in theory be no reason for alterations like this. 401s usually behave well, but often in desparate need of thorough cleaning and oiling.

Rocketeer

I know, this is what's making me crazy about it. In theory it should work just fine. But there are a couple of others who have had this exact problem.

All the parts were initially original to the machine, and it was cleaned and completely retimed, checking all the parameters including hook timing, gaps and thread clearances, etc. It just kept happening despite my swapping multiple variables.
Sure works perfectly now

bkay

Great! I'm glad your problem is solved. I didn't mean to minimize your solution, as my problem might not have been the same. The thread would get tangled up in the bobbin area. I would have to cut the thread to get the fabric out and by then, you couldn't tell where it was hanging up. Similar to your situation, it was intermittent.

I had already cleaned the bobbin area in what I thought was extensively, but it was suggested that I do it again. I watched a you tube video on cleaning the bobbin area extensively with q-tips and sewing machine oil. I followed the example and the problem stopped.

I posted photos of the gunk I got out of the area, but couldn't find the post.

Barbara

Rocketeer

Oh I didn't think you were minimizing the problem at all -- and it *must* be rare, because these things are workhorses and not "notorious for problems" thankfully : )