When a mechanical sewing machine sits unused for a long time, the old oil turns into glue. In the top of the machine, everything needs to move freely to get the zig-zag or other stitches working. At the shop, I remove the old oil with WD-40. Just spray it in, then work all of the mechanisms by running the machine, or by moving the parts by hand. Set the zig-zag at it's widest, then work the needle bar side to side. Then see what the needle bar moves, and work that mechanism. Keep working and moving everything until it's moving freely. Then it's important to remove the WD-40. I use an air compressor and flannel rags. After the WD-40 is removed, re-oil.
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