Janome 9000 top tread breaking changed needle, checked feed through several times

Make sure the correct length of needle is used and installed correctly. Sometimes it moves slightly out of the holder without falling out but just enough to affect the needle eye position which can cause this kind of problem. For thicker materials use either ball point or denim needles. As last resort the top thread tension might be too tight. Adjust the top thread tension.

Could be the result of several things. There could be some gunk or threads stuck in the tension disk. Be sure to remove the thread and rethread from the beginning in the order specified. ALWAYS RAISE the presser foot when threading!!!! If you haven't tried a brand new needle, do so, and make sure it is pushed all the way up and installed with the flat side facing the correct direction. Some machines recommend #90 as the largest needle to use. Also, perhaps the needle eye is too small to accommodate the thread. Watch where the thread is breaking to give you an idea of where the problem may originate. Try a different brand of thread. Sometimes black thread causes issues because the heavy dye affects the thread. Set the tensions at the midway point and then loosen the tension on that one needle. There could also be a burr or rough spot somewhere along the threadpath that is catching the thread. Last idea--could be a timing issue.

Serger needle thread breaking sewing discussion topic PatternReview com

http://www.amitymama.com/threads/anyone-have-an-idea-why-my-serger-needle-thread-keeps-breaking.280524

Make It Handmade Threading Your Serger or Overlocker

Help please Serger needle thread breaking

Sewing Machine Thread Keeps Breaking

There are several common reasons for upper thread breakage.

Check that the needle/thread/fabric are compatible.
All About Needles

Remove the upper thread from the machine, install a brand new needle, ALWAYS RAISE the presser foot, and rethread from the beginning. Verify the thread path is correct. Set the upper tension to the midway point.

NMSU Checklist of Common Machine Troubles

Sewing Machine Problem 1 Thread Breakage

Sewing Machine Thread Keeps Breaking

Why Does My Thread Keep Breaking While Sew

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change the needle--
Correct needle insertion is mandatory for proper use of your sewing machine.
Raise the needle bar to the highest point, then loosen the needle clamp screw to remove the old needle.
Place the new needle in the needle clamp with the flat side of the needle facing the back, (round needle, the groove in the needle should face away from the shaft).
Push the needle all the way up as far as it will go. Then tighten the needle clamp screw.

rethread the top thread--top & bobbin
check the bobbin to make sure the bobbin is not damaged
reinsert the bobbin in the case correctly

If the thread breaks at the needle and is feeding smoothly from the spool, you may have the tension too high. It is impossible to say what the setting should be because the knob rotates all the way around several times. Loosen it off until you see needle thread pull to the back of the quilt, then tighten until it just balances the interlocking of the stitch in the fabric. Test with little swirls, that's most likely to pull needle thread to back.Also, check that the needle is properly installed and that the hook to needle timing and clearance are good.Nesting of thread underneath usually happens if the foot lifter is left up or the tread is not fully in the disks of the tension unit.

rethread the machine getting every thread guide
check the thread tension 3 or 4 is usually good
Change needle--make sure the flat side is toward the back of the machine & that it's insert as high as it will go--make sure the needle bar is raised to it's highest position
Clean under needle plate where feed dogs are for lint
Clean bobbin area for lint or loose threads
Rethread machine top thread make sure to get every thread guide
& bobbin that the bobbin is wound correctly & put into the bobbin case or shuttle correctly

here a tip about needle & thread compatability
Cut 6-8 inch piece of thread of the spool you are going to use for your project
Take the needle you are going to use for the project
& insert the thread thru the eye of the needle
& lift one end of the thread to a 45 degree angle
& if the needle is the right size for the thread it will slide down the thread
But if the needle hangs on the thread you need one size larger needle for the thread

I had a similar problem and then realized that the thread on the top had a **** on the spool it was catching on.

Several possibilities
1. The needle thread is not threaded properly.
2. The needle thread tension is too tight.
3. The needle is bent or blunt.
4. The needle is incorrectly inserted.
5. The fabric is not being drawn to the back when sewing is finished.
6. The thread is either too heavy or too fine for the needle.
7. Old perished thread. Use quality thread for best results. 8. Needleplate burred near hole, from needlestrikes 9. Hook is burred (Feel the tip of the hook under bobbincase with your finger....polish with 1600 emery paper carefully)

your needle needs to be replaced and make sure it is in correctly..if this does not work you will need to make sure your thread is not old. then adjust you bobbin tension...there are 2 tensions on machine top and bobbin

I think you may have to use some sort of tear away paper on top of the loops so the needle doesn't get caught, as well as stabiliser underneath. I just checked the manual for my janome and that's what it says for towelling.