Juki 8500ddl thread pulls out of needle after first stitch

Question edited for clarity.

Back to basics. Unthread the machine. Remove the bobbin and make sure is is correctly located and lock. Re-thread the top end. Make sure the thread is through the eye of the needle and has a long tail.

https://www.google.com/search?q=Juki+Dnu-241h+not+stitching

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Possibly some other things, ie the wrong type of needle for the thread and fabric, using old or bargain bin thread...

Basic Maintenance Tension Skipped Stitches

What to Do If Your Sewing Machine Is Skipping Stitches

Don Ignore Your Sewing Machine Skipping Stitches Simple Solutions

replacing the bobbin carrier has upset the needle/hook timing
readjust or take it to a machine shop to have it adjusted

Make sure you are threaded correctly. Also be sure that your bobbin is sitting in the casing correctly. If the timing is right and the hook is catching, the thread may not be pulling through correctly. Clean your machine as well. Make sure your tension spring is clean and doesn't need to be tuned up.

try adjusting the top thread tension and see if that helps
also try changing the thread.
also change the needle--make sure it's the right needle for the fabric
being sewed.

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.

perhaps you have the wrong needle or its not in the proper position?

How to Thread Juki MO-134 Serger from watching lady at Lyles. Turn upper blade up. Push in first then turn up.It makes threading easier. Blue Thread upper looper first. Pull thread through tension knob. Don'tjust lay it there. (She thought that is what I must have done) Orange Thread lower looper next. Pull thread through tension knob as inthreading upper looper. Adjust lower looper so it is right nextto upper looper so that their points are almost together and directly belowsewing needles. Lower looper will be in front of upper looper (I believe). With tread from upper looper pulledback, slightly lift lower looper above upper looper and thread. I think this isright. Pull thread back with other thread. Tension is the key. Remember that. Yellow: Thread left needle first.Remember tension. Pull thread through curled wire on left side of needle arm. Green: Thread right needle. Rememberabout tension. Pull thread through curled wire on right side of needle arm. b> Note: Before sewing turn the wheel tomake sure the stitches are going together correctly.

Hi. Skipped stitches are usually caused by a mismatch in your thread and needle. Wrong thread type, wrong needle size, or even old thread can cause skipped stitches. If all else fails, change the needle. If that doesn't work, clean the machine. Sometimes just getting rid of all the lint and giving her a good oiling does a world of good.

Let me know if this works.

Robbie

What bobbins do I use on a Juki DDL-8300