My lowerlooper thread keeps breaking. I can only

increase the needle thread tension up more

Hopefully, it was recently serviced. Take it back and have the technician take another look at it. Do NOT unthread it (just clip the threads below the thread tree) when bringing it in so the technician can verify it is threaded correctly and also see where it may be hanging up.

If the top thread sews a few inches and then breaks, something is catching the top thread and holding it until it breaks. Usually, this will happen when using the old style thread cones with the slit in the edge to keep the thread from raveling off the spool. To prevent the thread from hanging up, turn the thread spool over so the slit is at the top instead of the bottom. Sometimes top thread breaks will happen if the thread becomes looped around the thread spool pin.

Remove the thread, ALWAYS RAISE the presser foot and then rethread the upper thread. Verify that the thread path is correct and that the thread has not looped around a guide.

If the thread is fraying at the needle eye, the needle/thread are not compatible. Also, the tension may be too high.

Check that the upper tension disk is clean--no gunk buildup or thread pieces stuck.

If the thread is actually breaking when it penetrates the needle plate hole, there may be a burr or nick somewhere below that is catching the upper thread. You can wrap your finger with a piece of fine fabric, like an old pair of hosier, fine knit fabric, etc. and running your finger around in the bobbin area, under the needle plate. If you get snags, then you have a burr or nick. If it is small, you can sometimes smooth it with a fine emery board. If it is a large burr, you may need to purchase a replacement part.


Why Does My Top Thread Keep Breaking Sewing Machine

Sewing Machine Problem 1 Thread Breakage

Sewing Machine Thread Keeps Breaking

...

Skipping stitches and thread breaks
Skipping stitches and thread breaks

Sewing Machine Thread Bunching Up? Here's Why!
Sewing Machine Thread Bunching Up Here Why

It may be a tension or a threading problem. There are videos on youtube that may help. Change wording on youtube search to find issues that match your problems. Follow link.
sewing machine problems YouTube

The top thread breaks
1. the needle thread is not threaded properly
2. The needle thread tension is to tight
3. The needle is bent or blunt
4. The needle is incorrectly inserted
5. The needle thread & the bobbin thread are not set under the presser foot when starting to sew
6. the threads were not drawn to the rear after sewing
7. The thread is either to heavy or to fine for the needle

Make sure you are threading the machine correctly. Make sure you are using serger thread that isn't old. Make sure you are undoing all the threads when it breaks and thread it from the beginning.

Make sure you have the right needles in their respective places. My Juki MO has two different size needles.

check to see if there are any burrs in that area

Good day!

please try this simple tips:

Good day!

A sewing machine operator can often help themselves when their machine does not operate properly.
Here are some simple instructions, which if properly used can save time and mechanics service calls.
TROUBLE;UPPER THREAD KEEPS BREAKING;
This could be trouble;================Do this;
1.Top tension to tight================loosen tension 1 turn
2.Machine improperly threaded=========check threading
3.Thread twisted on guide post========"
4.Thread twisted out of tension======="
5.Take up spring bent or broken=======Check action of spring
6.Thread jumped off pull off finger===Check threading
7.Needle bent or burred===============new needle
8.Bad cone of thread==================try another cone
TROUBLE;LOWER THREAD KEEPS BREAKING;
1.Bobbin tensionspring to tight=======Loosen tension slightly
2.Bobbin threaded wrong===============check threading
3.Bobbin wound to tight or uneven=====try new bobbin
4.lint or thread on bobbin case=======clean inside case
5.Lint or thread inside hook==========clean inside hook
6.Bobbin case nicked bent or burred===check/change case
TROUBLE;MACHINE STARTED SKIPPING STITCHES;
1.Needle bent or burred===============change
2.Needle set in crooked===============Check
3.Thread jumped off take up spring====check threading
4.Thread jumped off pull off finger===check threading
TROUBLE STITCHES SHOWING LOOPS;
1.Forming loops on top of cloth=======Tighten bobbin tension
======================================or loosen top tension.
2.forming loops on bottom of cloth====Tighten top tension
3.Bobbin placed in case incorrectly===remove and replace
4.Bobbin thread slipped from under====check threading of
tension===============================bobbin case
5.Lint or thread in top tension=======clean between tension discs


Thank you and good luck.

Refer to the manual for threading and thread the machine with the presser foot up.

Make sure the bobbin is inserted so the bobbin thread is feeding in the correct direction from the bobbin spool and through the proper guides.