The looper door on my new over locker is not closing tight?

As a general rule the left cover needs to have its top aligned with the plate and then tapped shut with your hand until it catches. The front cover that I believe you are asking about, should lay flat when you are threading it, and then you pull it to the right as you are closing it and then it will catch the latch as it slides into place beside the knives. If this is not happening, I would check down in the hinge and see if there is something caught in it, such as a piece of lint or material. Use your vacuum cleaner hose to sweep out the hinge if there is alot of lint or you can use canned air if there is just minor lint. Then use an old toothbrush to brush across the hinge to make positive it is clean and try to close again. Good Luck.

Search the internet. There are web sites and videos that show machine timing, although adjusting a serger may a bit more challenging.

...

Here is your Manual:

JUKI MO 644D Instruction Manual

Go back to the seller. If it was listed as new and does not work, the seller should either repair, replace, or refund. Note--you may need to get eBay involved in case the seller refuses to address the issue. EBay will refund your money and reverse the charge to the seller.

you have to get the door fixed, juki is set up to power off if the door is open for safety reasons

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.

Open the font of the serger and the instructions will be printed on the serger or on the door.

Raise the presser foot and set the tensions to zero when threading.

Turn the hand wheel so the upper looper (curved one) is at it's highest point and thread it first, and then the lower looper.

With some sergers you must thread in a certain sequence. This should be indicated in the instructions on the serger.

Set the tensions back to normal ( 4 - 6), lower the presser foot and run a length of stitching to see if the threads are knitted together as they should before you start serging your project.

Put new needles in it.

Following the colors, thread the upper looper first, then the lower looper. Next thread the needles. Always thread in this order.

Loopers are probably out of time. I'd suggest calling a good mechanic. This takes some skill and experience to do. As long as the looper tips are not broken, it can probably be retimed within an hours time.

Well, you might just need a good oiling. Make sure the machine is not threaded and there are no thread snarls where the loopers interact. It also pays to insert new needles and observe the loopers and needles interact. they should come withn .01-.5mm of touching eachother; there should be no hard positive contact between loopers and needles. So, if its tight to turn over by had, this is usually a cam or bushing that need oiling, or thread that got sucked into the machine and is binding the thing up. What I would do is remove the covers, slip the motor belt off, turn over by hand. If it frees up, the bind is in the motor, if its still tight, then id look for thread, and oil the machine with a light weight oil (sew mach oil, tri-flow... NOT 3in1 oil!). If you have a keen eye, you can wiggle the handwheel and try to observe what parts are moving slightly, and which are not. using that method you may be able to track the bind to a section of the machine or even a specific shaft/cam/component of the machine. Another common bind point in sergers is where the knives mate. Move the top knife to its idle (non cuttin) position and see if this relieves the bind.