Janome MC 500e
 

My embroidery machine leaves loops and matted treads on the back. I have taken it in to the dealer/repair person here 4 times. It works for a day or two and Then starts doing the same thing again. I have changed tension, cleaned, rethreaded, replaced bobbin case and thread both bobbin and top. It was cleaned and oiled by dealer. I’m totally frustrated. Any suggestions?

If you can pull the thread through easily when the foot is down, it's your tension. Lift the foot and re-thread, make sure the thread sets firmly in the tension discs, then test again with the foot down. You cannot thread properly when the foot is down as it closes the discs so thread cannot sit between them. Hope this works for you.

What bobbins are you using in the machine? You might try the pre-wound for your machine. Re-check that you are using the correct size bobbin. I only use the bobbin brand for my machine and not universal ones.

My embroidery machine has two different bobbin cases. I had to change to the other case and no more issues. It had something to do with the set screw being fixed in one bobbin and adjustable in the other bobbin.

What needle size and type are you using? I think there are brand specific needles for your machine. I use Schmetz Micro-tex 80/12 for most of my EMB and sewing projects. Be sure the needle is inserted all the way UP into position.

What type of stabilizer are you using? What type of project? What design?

Does the machine work with other designs or sewing (if a combo machine)?

What thread are you using? Are you hooping the project or floating ITH? Does this happen with different brands of thread?

Here's a fun project for Janome 500e. Flamingos , the fluffy feathers are done in satin stitch really,really long and stitched in circles.There are about 25 circles in this patch.Once its finished turn it over to back and snip the satin stitch in the center of the circle turn around to the face and tease the stitches back out with a knitting needle or something similar.There are other files like this such as Cats dogs other types birds ie;emu's ostrich ect.

I would take the machine to your dealer as soon as it starts doing this....if you can. don't change anything before you go to their store.
I have heard that the Janome 500e is a great machine. Good luck.

ZooAnimals, You really need to post a new thread about these flamingos. They look great and more people need to see them!

I really suspect it is your top tension. Mine does this sometimes…I take cover off…there’s a spring that pushes the tension discs together. I adjust @ test pulling thread with foot down. My Brother is older and this happens frequently.

I think the problems must have been resolved as there hasen't been any follow up. I have a Janome 550e and I usually fix these type of nuisance's, 1 Re thread from #1 through 2 change needle 3 change bobbin.this is usually the main contender .if it happen again x 2, I throw out the bobbin there is a problem with the wound tension or the spool is damaged. 4 clean out the bobbin case fluff or bit of thread can cause havoc. 5 If fraying continues I toss the spool of thread. 6 check bobbin case that its not damaged from needle strike. I think "Kiddynurse" main problem is the bobbin,if they are using the 500e bobbin winder it's the worst bobbin winder Janome has ever put on a machine.They should try brought bobbins to start with and then bobbins wound on a machine that has a separate winder motor..I do wind my bobbins but do it on the 6700P far superior in tension to 550e winder just absolute junk..As far to adjust tension on 500e you cant it automatic.

Janome MC 500e
 

Yes does happen to this machine. I learned that I will go 5 to 6 switches, then stop the machine and pull the loose end of the thread until it's firm to the fabric. Cut off the loose end.
The other times I end up with a ball of thread on the back side of the pattern is when thread has caught in the thread cutting area of the bobbin case. I take the cover off and clean out the bobbin case.
Usually I can hear if the machine is starting to form the mess on the underside of the pattern. I have also found some manufactured embroidery thread is more prone to this than others. I like the machine a lot, and have made many items from cup sleeves to kitchen towels and pillow cases. It's been a wonderful experience. People reaction to an embroidered item is fun to watch.