For whatever reason top loading sewing machines can jam, most of the time you can simply find a tangle of thread and remove it, and start stitching again. However, if yo are unlucky and had a large jam up, which sometimes happens if the machine is not threaded correctly, or the user is pulling the fabric through. When this happens the bobbin case can be forced past its stopper spring and will need to be reset. This can be done by following the pointers below or checking the machines user guide.
1 Remove the needle plate on the machine, usually held down by two screws.
2 Now, you can now see the plastic bobbin case. The outer edge should be very smooth with no burs or needle marks, the edge is not a full circle, it has a small V shaped indentation, with a bulbous stubby protrusion, called a Butt, and this comes up against the bobbin case stopper spring. The bobbin case spring stopper is located at the 5 o'clock position as viewed from the front of the machine. If jammed the Butt will now have jumped past the stopper spring clip.
3 Remove the jammed bobbin case and check for any damage, light damage can be smoothed by using fine emery paper, heavy damage and the case will need to be replaced.
4 Re-seat the bobbin case in the correct position so that the V shaped butt comes up against the bobbin stopper spring when it is resting on the metal hook. There should be a small amount of movement in the bobbin case as it lets the thread whip round it a speed, the rotation clearence should be no more than 1 mm
5 Re-attach the needle plate, check your threading and try again.