Lower looper air threader will not thread on baby lock imagine serger

http://www.sewingpartsonline.com/generic-threader-looper-for-brass-overlocks.aspx

These machines have to have the threader tubes engaged. Do you have them set for threading? If it still doesn't thread you have to use the wire threader that was provided with the machine when you bought it. It might be in the storage compartment under the lower looper spool pin.

I "THINK" I have my machine threaded properly but it will not make a chain stitch. I followed the thread guide for the narrow three spool set up with the right needle setting.
why would the machine not catch the chain ????

Apparently either you have no needle threaded to lock the stitch or both loopers aren't correctly threaded. You must thread your UPPER looper first (don't know what color yours is), LOWER looper next, RIGHT needle next and last the LEFT needle if you are using the 4 thread overlock stitch. It sounds like you are having trouble with your lower looper. Look for the lower looper threader to help you thread it. Your manual should show you a picture.

This is the lever on the air-jet threader?

You might try the sew4less website, but may have to go to the BL dealer for this.

There is a wire threader that came with the serger that you can insert into the thread port to make sure the entry is not clogged with a broken thread.

I lost mine and use a length of fishing line.

Open the front cover and raise presser foot to release all threads. Depress the machine lock button firmly with your left index finger. At the same time manually rotate the machine hand wheel slowly forward until he button "snaps" into the locked position and the lock button release lever moves to the far left.

You have to get the replacement wires from a Babylock dealer, I did too then after sticker shock at the price of that wire I learned to make a thread cradle and use that to thread difficult threads no. Take about 24 inches of regular sewing thread and fold it in half, put the open ends (together, same legnth) into the jet air port and hold onto the loop end, press the jet air threader and it will thread the machine, insert the thread you want to use into the loop you have in your hand and pull it thru the machine using the ends of the thread you put thru the machine, sounds harder than it is and works all the time. No more spending $8 on replacement wires. You can use this method for all the jet air sergers.

The part number is B8200-01a and you can get it from any authorized babylock dealer.
Give them this number and they can order it.

On rare occasions lint can clog the yubes on these sergers. One of the first things I do is thread the wire through in the opposite direction. It will sometimes push the blockage out. The other option is to use an air compressor and again blow the lint out from the opposite side. If this does not work take it to a service man.