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| The 411G has gold accents |
The symptoms were that threads were nesting badly in the bobbin area. After perusing the 401 service manual thanks to Sewing Dude (https://sewingdude.files.wordpress.com/2012/09/singer-401-service-manual1.pdf page 131), I decided to go through and check the clearances for the bobbin case (which seemed very loose even before I cleaned it) and anything else in the bobbin area.
So this is the procedure:
Remove the needle, remove the presser foot, slide the slide plate (1) back, lift and remove the stitch plate (2).
If you want to (it's not necessary) you can also remove the slide plate. It's just like the 66 and 99. Put down the platform that holds the stitch plate then slide the plate back until it clears the spring.
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| You should now see this (without the arrows of course) |
You will need a set of narrow feeler gauges to check the clearance. If you don't have any, you'll need to get some or guess the gap.
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| Narrow feeler gauges |
Using the picture with the arrows, check the gap marked 1. It should be 12-14 thousandths of an inch (thou). If it's not in that range, go on to check 2, the vertical clearance between the hook and the spring, 16-18 thou. These are both adjusted at the same time, by loosening the two screws marked by thick white arrows and moving it until the clearance is right, then re-tighten the screws.
Once you've done this, check 3, the distance between the bobbin case and the spring. If this is not between 12 and 14 thou, adjust it. The adjustment is easy, but you first need to remove the machine's plastic base (two screws), exposing the locking screw (see picture below).
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| lock screw for adjusting bobbin case clearance |
Once you've loosened it, you can turn the screw to the right of the bobbin spring (see below) which is eccentric and will increase or decrease the gap.
Once this clearance is right, perform a test sew. My machine was made to sew at full speed with a very narrow stitch length and making a pattern, the ultimate test. It didn't skip any stitches or even hint of bunching up. Machines like this that do everything are a lot more complex than, say, a 15 or 201 so they need more attention and are harder to get to, but with the right resources (mostly just knowledge) you can keep them in top condition.
Another problem was varying speed during sewing. This means that the foot controller's carbon pile needs a clean. This is a horrible job, so I replaced the controller. Later on I pulled out a Japanese electronic controller I've had for a few years and that was even better, because apparently you can leave these plugged in without any heating (the 411's controller was also quite hot when I changed it). The electronic replacement required a little soldering.
It's now almost perfect. The last job is to see why the motor is noisy. A drop of tri-flow was suggested on another blog, but it hasn't quietened it, so I'm thinking I'll have to remove and disassemble. Not a job I'm looking forward to, since it's completely enclosed, but I'll do it and let you know of any obstacles.
