When I sew or embroider on my janome 9700 the top thread loops leaving little bumps on the lower stitching. It doesn`t matter which tension number I use on the wheel - still get the same problem. Should I mess with the bobbin holder? How do I alter the tension on this. Does the tension wheel get stuck at all and would this be a computerised problem? thanks

Question edited for clarity.
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Sewing machine tension is a delicate tug of war between the bottom Bobbin tension and the Upper tension to put the loop between the 2 layers of fabric. You set the Bobbin tension first and the the top tension depends on the fabric and the thread used.

Your Bobbin tension is very very loose to be not tensioning at all or the top tension is too loose.

Adjusting The Tension - Janome Memory Craft 6500 ...

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Janome Memory Craft 6500 Professional Manual Online: balancing thread tension, Adjusting The Tension. Correct Tension: The Ideal Straight Stitch Has Threads ...

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Most likely, the bobbin thread is not in the bobbin tension. Rethread the bobbin and try again.

Loops on top of the fabric almost always mean too little tension on the bobbin thread; loops on the underside almost always mean too little tension on the top thread. Just backwards of most people's first guess. See http://www.picturetrail.com/sfx/album/view/22521551

I think you are saying that there is a loop showing on the bottom of the lower thread stitch. If the lower stitch looks correct and not bunching, you will need to change the tension on the upper stitch. Make sure that your threads are firmly inserted within the discs also before adjusting the tension. It doesn't take much to change the tension so take it slowly.

Little fingers can cause issues, especially if you leave the machine out.

Now, Loosen the top tension.
Take out the bobbin shuttle and locate the little screws. Tighten them 1/8 to 1/4 turn. Do a test seam. Keep working this way until you get LOOPS ON BOTTOM... then tighten the top tension until you get a balanced stitch.

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.

If the loops are forming on the bottom it is the TOP thread tension you need to check. Make sure it isn't too loose. Also is the needle the right type and size for the fabric? Check the stitch out on plain cotton fabric if a tension adjustment doesn't fix it.

The TOP thread effects the UNDERSIDE of the stitch and the BOBBIN thread effects the TOPSIDE of the stitch :)

Usually If the underneath is loose it is the top tension that is the problem. If it is the top stitching that is loose it is the bottom tension. Hope this helps.

Tighten the bobbin thread a little and loosen the top thread tension a little. A correctly tensioned embroidery machine will show a little less than 1/3 of the top thread color and 2/3 of the bobbin thread on the bottom side of the embroidered piece. You may have to play with it some so use scrap material and dark top thread until you get your adjustment made.

#14 needle is way big for cotton napkin scrap. a #10 is good for most lightweight fabric. #14 is for sewing denim or levis, like that.

the tension problems on almost all machines regardless of price usually fall on the upper tension. the lower bobbin tension is factory set and it's rare you should ever need to mess with it.

if you have a drop in bobbin (top loading), tighten the adjustment screw all the way and then back it off 1/4 turn. if your machine uses a shuttle bobbin, tighten the adjustment screw all the way and then back it off in 1/4-turn increments until you can hold it in the air like a yo-yo and cause to bobbin case to fall slightly dipping your hand.

A dull needle and stitch length will also mess up your stitch. The idea is to narrow the problem down to one thing and one thing only -- UPPER THREAD TENSION.

So, if you have the right size needle for the job, with the right thread, and if your stitch length selection is correct (usually between 2 and 3 or 8-to-10 stitches per inch, the problem should be with your upper thread tension.

An easy way to fix this then is to remember: Loops on top, upper tension drop. Loops below, upper tension grow. If you get loops on top of your work, lower (drop) your upper thread tension to a lower number. If you get loops on the bottom, raise the upper thread tension.

Different stitches on the same machine will require different upper thread tension settings. Don't be afraid of it. Just remember the pneumonic: loops on top, tension drop, loops below, tension grow -- referring to upper thread tension.

have fun :)

Sounds like the bobbin tension is loose. Look at this website on their "repair" page where it explains how to adjust the bottom(bobbin) tension.
www.sewusa.com