CLEANING AND OILING. Remove the upper thread, bottom bobbin or shuttle and needle. With the presser foot up, try to run the machine at full speed for one minute. If you hear a noticeable variation of the speed, your machine may need some oil. If you still have the manual then follow it. If not, proceed like this: try to remove the top cover if your machine has one. If not, you should be able to find holes on top of it. Apply only a drop of SEWING MACHINE OIL (not 3 in 1 oil or any other kind of oil or rust inhibitor). Next, reach the bottom of your machine. If it is equipped with a base cover, try to remove it to gain access to the mechanism. After removing any dust, lint, broken needles debris and straight pins, apply a drop of oil to each moving part. By turning the hand wheel slowly (always towards you for 98% of them), you will see all the moving parts joints that needs to be oiled. Many parts already have a small hole especially for oiling. Remember one small drop of oil in each joint is enough! Please note: If your machine’s handwheel turns towards the back like the old White-Rotary, always turn it the same way!
THE FEED DOGS. With a flat screwdriver, remove the needle plate retained by 2 screws. On some Elna, Pfaff and Bernina models, you will have to remove the bed’s top plate on which the needle plate is fixed. Some of them are snapped in place and no screws are holding them. When removed, clean the feed dogs. Try to pass a rag under them and with an old needle or narrow tool, remove the lint inside the feed channels. Put back the needle plate. If your machine is equipped with a FEED DROP, be sure the feeds are set at UP position. By turning the hand wheel (towards you), check to see if the feeds make their movement. While doing this, you may check also the reverse mechanism to see if the feed dogs moves backward. If the feeds does not move at all, a major problem occurred, do not go further!
THE UPPER TENSION. Most sewing machine problems are related to the thread tension. Learn this basic principle right now: the upper tension determines your UNDER stitch. And the bobbin (bottom) tension determines your UPPER stitch. Unless you are experimented to dismantle the upper tension unit or if it’s explained in your manual, follow this simple technique. Dust, lint and pieces of broken thread often stick between the tension discs. This cause a gap between the tension discs and no pressure is applied to the thread resulting of thread loops underneath. Take an 8" length of thread and make 3 to 4 knots in it (as pictured below). Thread your tension system with this piece of thread a few times in all directions. This will remove any lint residue between the tension discs. Try it for the first time with the presser foot UP and then with the presser foot DOWN. When the presser foot is down and the tension dial set at number 4, you should be able to feel a tension when pulling the thread. If so, the upper tension system is working properly.