Hi I just purchased a used Juki DDL-555. 1) It will not catch the bobbin thread. 2) it will not sew forward and feed the fabric along (it sews in reverse just fine). Can someone please help?

The best source of information is your owner's manual. Perhaps this will help you:

Juki 227 552 553 555 Sewing Machine Threading Diagram


...

go to the Juki website and ask them about a manual and bobbins

Sounds like you've over oiled your machine. Take the bobbin out, strip the thread from it. wipe it down well... and re-wind the bobbin with new thread.

Next time you oil after your day of sewing. Place a piece of absorbent scrap fabric under the presser foot to catch excess drips.

Your needle probably bent and got jammed. clip threads top and bottom of the fabric and remove... then get in the bobbin area and look for issues.

Regular sewing machine needles. Choose the needle type and size according to the type fabric or thread being used.

http://www.euronotions.com/pdf/Schmetz_Sales_Guide.pdf

Hi, if your ddl-555 sewing machine the needle doesn't grab the string from the top and bottom; and it can't sew the fabric. Do you know what to do/

Sounds like as the machine builds up friction from extended use, some vital part is lacking lubrication and is seizing up. A good service person will remove ALL of the covers and thoroughly air clean and oil every moving part. Sometimes these dry points are hard to find and patience is required.

You can get a sewing machine oiler with a long applicator and put a drop of oil on anything that moves, but over oiling can be messy.

im no expert, just been sewing for many years, i use 2 different juki machines, i suggest looking at the needle, are we sure you have the rite size? 135/ 140? did the needle just get changed? it could be the correct one, but if its in backwards, there isn't a dimple to let the hook behind the thread, to catch it, feel free to call me, 239-895-4845, my name is devin, shop is Quality Auto Trim Inc., ill try to help you over the phone if necessary, good luck

What bobbins do I use on a Juki DDL-8300

MAKE SURE YOU HAVE THE RIGHT NEEDLE FOR THE THREAD YOU ARE USING, AND THAT THE SAME THREAD IS ALSO IN THE BOBBIN. CHECK UPPER TENSION, BY PULLING SLIGHTLY, IF IT'S TIGHT, LOOSEN THE UPPER TENSION.YOUR THREAD MAY BE THE WRONG SIZE OR TYPE FOR THE SPEED YOUR SEWING., and the needle your are using( sorry about the caps lock)