The threading on the machine is improper.

Remedy

Make sure that the threads are passed into the machine properly.
Rethread the threads to the machine in an appropriate procedure.

Refer to the detailed instructions to learn the threading procedure.

Instructions for threading the machine.

You can also see the instructions for threading on movie.

Video instructions for threading.

Thread is tangled.

Remedy

Check the spool pin, thread holders, etc., and remove the tangled thread.

The needle is bent, or the tip of needle is blunt or broken.

Remedy

Replace with a new needle.

Thread tension is too tight.

Remedy

Adjust the thread tension properly.

Position "4" on the tension dial is the standard of thread tension. Start the adjustment with "4" when adjusting thread tension. When adjusting the thread tension, change the tension dial position little by little and then check the sewing result with trial sewing.

Refer to the instructions to learn the adjustment of thread tension.

Instructions for adjustment of thread tension.

Needle is installed incorrectly.

Remedy

Reinstall needles correctly.
Make sure that the needle is installed until it touches the needle stopper.

Wrong needle is used.

Remedy

Use a standard home sewing machine needle. The recommended needle is 130/705H (#90).