Good diagram showing how to thread a 4 thread Juki 644d serger we do not have a manual machine is not clear

You can download a free threading guide here - http://www.sewusa.com/Threading_Diagrams/Threading_Pages/Juki_Sewing_machine_threading/Juki_MO_644_Threading_Diagram.htm

The same site also sells manuals.

Threading Tips:

Have the thread antenna at it's highest position.

Set the tensions to zero.

Have the presser foot up while threading.

When you thread a serger for the first time, or if you are having a threading problem, use a different color thread for each guide. This can quickly indicate where the problem lies.

Once the stitch is satisfactory, change to the color you prefer - but this way is the easiest - cut the thread near the thread cone and tie off with the new thread. With the tensions at zero, slowing run the serger until the new thread appears. You will need to stop as the knots approach the needles and thread them by hand.

Do the tie-off before running out of thread and this will save a lot of time and stress.

Should the needle on the right be slightly longer than the one on the left after inserted?

I'm having great difficulty THREADING the juki mo103n serger. It's driving me nuts. Please help on line. thx