Thread tension won't adjust properly. Top thread is ok, bottom ,

Check bottom thread (bobbin) tension.
Pinch bottom thread (bobbin) between finger and thumb and make a low steady pull. The thread should come off smoothly with moderate tension. If it snags or catches, check the bobbin is load per instructions.

If this model has a transparent bobbin cover, when the bobbin has properly loaded its tensioner, you should see the bobbin thread over and across the top of the bobbin. If you don't, likely the thread has escaped the bobbin tensioner and you'll need to reload the bobbin.

Check top thread tension.
To check top thread tension, move presser foot up, then make slow steady pull of the top thread. The thread should advance smoothly without hesitation since raising the foot releases the top thread tensioner.

Next, rotate the tension selector to 4, lower the foot, and again make a slow steady pull. You should feel the difference in tension and thread should advance smoothly. If you adjust the tensioner while pulling top thread you should feel the change in tension.

If you find there is no top thread tension, then you need to rethread top thread and set tension per instructions.

indications of a bobbin tension incorrect is the bottom thread lies flat under the bottom material
it seldom needs adjusting but if you have to the spring plate that you pull the thread under as you put the bobbin back in the holder is where you adjust it
there is a small screw that holds that plate on so the slightest movement of the screw makes a lot of difference of the thread tension
all thread tension problems relate to the needle thread tension and if you have it set to 0 then the thread will be bunching up under the material
you don't say what the issues are but pounds to peanuts , it will be the top tension that is the problem
It will be correct when you are threading the needle , you pull the thread out first before threading and there is a resistance to pulling the thread

When your bottom thread is messy it is the top thread needing adjustment. Your machine may not be threaded properly and the thread may not be sitting correctly between the tension discs.
Check to make sure your machine is threaded correctly.
Check thread between the tension discs.
After checking, adjust the tension (tighter) and do a test. If it is still messy add some more tension and do another test.

Adjust your tension knob.

If the thread problem appears under the fabric, it is a top thread issue.

If the thread problem appears on the top of the fabric, the bobbin thread is the issue.

Perhaps the upper thread is not seated completely in the tension disk. Remove the upper thread from the machine, ALWAYS RAISE the presser foot, then rethread from the beginning. Make sure the thread path is correct. Test your stitch.

If the thread is still looping under the fabric, the upper tension is too loose. Set the upper tension to the midway point. Test and adjust the tension until it is where you want it. Preferred tension is when both threads meet in the middle of the fabric.

sewing machine tension Google Search


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The bobbin also has tension adjustment. Take bobbin out and try making it tighter. Also make sure thread is threaded properly on bobbin.

THE BOTTOM AND TOP THREADS ARE IN A TUG OF WAR. WHEN THE TOP IS TOO LOOSE THE BOBBIN WILL BE PULLING HARDER THAN THE TOP THREAD SO A GREAT DEAL MORE THREAD WILL END UP ON THE BOTTOM. TO CORRECT THIS YOU INCREASE THE TOP THREAD TENSION. IF THE TOP THREAD IS PULLING HARDER THAN THE BOTTOM THEN A GREAT DEAL MORE BOBBIN THREAD WILL END UP ON THE TOP. TO CORRECT THIS YOU WOULD LOWER THE TENSION ON TOP.

Hello

Adjust the tension

Load your sewing machine with one color on top, threaded through the needle. Load the second color thread into the bobbin and thread.


Fold the scrap fabric in half, and sew a straight stitch at least 2 inches long. Look closely at the seam. If you see loops of the bottom color thread on top of the fabric, proceed to Step 3. If you see loops of the top color thread on the bottom of the fabric, proceed to step 4.


Loosen the top tension. Since the top tension is so tight, it is pulling the bottom thread up through the fabric. Loosen the top tension by turning the numbered knob on the front of the sewing machine counterclockwise by one number.


Tighten the top tension. Since the top tension is too loose, the bottom thread is pulling the top thread down through the fabric. Tighten the top tension by turning the numbered knob on the front of the sewing machine clockwise by one number.


Sew a straight stitch 3 inches in length. Check the stitching. It is perfect if the threads meet in the middle, and you can only see the top thread on top and the bottom thread on bottom. If it still needs adjusting, go back to step 2 to repeat the needed steps.


Using two different colored threads makes it easier for you to see which thread is being pulled.

Always use proper precautions when working with electrical machines.

You can find a visual guide on the proper threading of your machine at http://www.sewusa.com/Threading_Diagrams/Threading_Pages/Consew_Sewing_Machine_Threading/consew_210_220_threading_diagram.htm. What other adjustments are you thinking of? If you have loose thread on the top or bottom, you would need to adjust the tension. The best way to do that is to start by having a different color thread in the top and in the bobbin. Then this little lesson on tension works the same with any machine.
Thread your machine with the presser foot UP. The disks that control the tension (threadgoes through them) are tightened up if the foot is down. Change the machine tension with the presser foot DOWN.Because the disks won't be engaged (see above) if the foot is up, the diskswon't move. Start at the middle setting, 3. Go up to tighten, decrease toloosen. Each machine is different, even 2 different machines of the same model.The best thing to do is start at 3 and use a different color in the top andbobbin thread so you can easily see what changes to the tension do to yourstitches. Now use a straight stitch a sew 3 or so inches. Take a lookat the top and bottom of the fabric. You don't want to see any (or at least notmuch) of the other color showing from the other side. Loops on the bottom of the fabric means you need to tighten(increase) your top tension. If you're stitches on the bottom are causingpuckering, then you need to loosen you're top tension. For the most part, youreally don't want to touch your bobbin tension-leave that to a repairtechnician. The factory setting shouldn't be touched except by someone whoreally knows what they're doing. Keep sewing a few inches at a time until you have the resultsyou want. Now you're tension is where you need it!

one screw should stay tightned .. the other is the adjustment ... you will notice that the correct screw is adjusting the force on a flat spring .. that spring is what provides the bottom tension .. when the thread is properly positioned then it will be pulled under that spring .. you should be able to pull the thread with just a small amount of drag .. the top tensioner should have about the same amount of drag when set to about 2 of its adjustment range .. usually the foot has to be down to engage the top tension ... you normally dont need oil on the bobbin case .. the screw you want is about in the center of the flat spring ... if you cant adjust the bottom tension then take the flat spring all the way off and see if there is thread or debree keeping it from operating properly .. make sure there are no sharp edges or burrs in the thread path ...