Objective: Identify and correct the three most common sewing faults on the Janome MC6650 and safely unpick a flawed seam so your sellable items stay professional.
Most stitch problems come from thread path or needle issues, not a broken machine. Read the fabric to locate the fault. Loose loops on the BOTTOM of the fabric mean the TOP thread is at fault — the top thread isn't seated in the tension discs, so re-thread with the presser foot UP (discs open) and make sure the thread snaps into the take-up lever. Loose loops on the TOP mean the BOBBIN is at fault — remove it, re-seat it so it turns the correct direction (on the MC6650 the drop-in bobbin should feed counter-clockwise so thread pulls to the right), and check it's threaded through the bobbin-case slot. Skipped stitches almost always mean a bent, dull, or wrong needle: replace it, flat side of the shank facing the back, pushed fully up. Puckered seams mean tension too tight, stitch length too short for the fabric, or a dull needle — lower the top tension dial a number, lengthen the stitch, and use the right needle for the fabric weight. When a seam is wrong, don't yank it; unpick it with a seam ripper. Slide the pointed tip under every third or fourth stitch on one side, cut, flip, and pull the single thread on the other side; it lifts out cleanly without stretching the fabric. Always test fixes on a scrap of the same fabric before returning to your project.