Hey everyone, I have a Kenmore sewing machine (385.12714090) that was passed to me from my grandmother. I used it to make some gear a few years ago, life got busy, and I just pulled it from the basement. It ran OK, but the thread tension was off and the stitch selector wasn't producing the correct stitches. I can't afford a service for it right now, so I opened it up. I was able to fix the stitch selector, which now works perfectly. Put a tiny bit of light oil everywhere the manual said to, blew out the fuzz and threads, and put it back together.
I did find a small, bent spring lying inside the case. I couldn't find where it was missing from. I don't think the engineers typically put in extra destroyed springs for fun, so.. I'm guessing something was damaged when I broke a needle trying to sew webbing straps a couple of years ago. I have not found what the spring went to, and I can't see any operational problems other than the issues I describe here.
Now everything runs smoothly, but I am having tension issues.
The problem: When the bobbin tension is set at a good starting point based on what I've read here and elsewhere (tick-tock motion of the bobbin case held by thread makes it move a little with every swing) and the top tension is set to mid range (4 on a 0-9 scale), I get massive loops/bird nesting on the bottom. When top tension is maxed, I still get loops on the bottom but they don't tangle.
As the bobbin tension is decreased, the problem decreases slightly. However, when bobbin tension is decreased completely (IE the screw is about to fall out) and top tension is maxed out, I still get symptoms of too-tight bobbin tension and too loose top tension - knot shows on the bottom of fabric, and the bottom thread is loose and just lays on the fabric on the bottom.
What I've done to troubleshoot:
-Rethreaded the machine 1000 times
-Changed thread both top and bottom (was using gutterman polyester, ran out, now using a cotton thread for testing purposes only)
-Carefully made sure the bobbin was loaded properly
-Checked top tension discs to make sure they're reinstalled correctly - when I put the top thread in and set it to 0, it takes much less force to pull the thread out than when I set the top tension to 9, so I know that the top tension discs are engaging the thread and the adjuster is producing a range of tension.
-Checked for burrs, dislodged or improperly installed parts around the bobbin case and surrounding area.
-Changed to brand new needles
-When I get a new spool of Gutterman thread, I will wind a brand new bobbin and try again (probably tomorrow)
-Using kenmore bobbins that came with the machine as well as third-party generic bobbins
-Problem occurs when using the motor and when turning manually
-all lines of stitches start with 3-4, then back to lock them in, then forwards.
-using straight stitch, setting of 2-3 for stitch length.
Manual/parts/model number here: http://www.searspartsdirect.com/part...d=&documentId=
So, for those of you experienced in troubleshooting sewing machines, what else would you check here? Are there any other problems that would present with symptoms of bobbin tension that is too high?
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