Specifically the cg754? Seriously, what is up with this thing? When it works, it works fine. When it doesn't...holy heck!
I received mine for Christmas last year and we've had our share of problems...snapping needles, tension issues, and it takes about a day to thread the thing...my husband has spent many a night sitting there behind the thing trying to figure out what's wrong. As of most recent, the problem is, big loops on the bottom of the fabric and something is hitting inside, something is banging when you try to serge....so these two problems are most likely related and husband said he has to take it all apart and possibly order new parts....I never did this, but after doing a search last night, I realized many people gave the same reviews as I did about this machine...people who have been sewing all their lives. I am so frustrated. Because I use the serger to make things that I sell. And we cannot afford another one. Unless I use this year's Christmas present. again. To ask for another serger. Blech. I mean....this thing was NOT cheap. Singer does not answer when you try to contact them for help. So....don't know whether it's worth fixing or not if we're just going to have problem after problem....and it could cost us my sanity!
I have that serger (I think it is the same one). I have not had problems to the extent that you have, but I have never been able to get it to sew a good solid seam. The stitches are always loose enough that the fabric pulls apart to show the thread. I don't know if it's my own incompetence or the machine itself. I've fiddled and fiddled with the tension.
I do not use mine heavily, though. At first I used it more, as I had an Etsy shop, but now I don't have that, so it's just used to finish the seams of an occasional item of clothing. I sew the seams on my sewing machine and then serge them to finish the edges.
Where was it bought? If it was bought from a dealer, you should get operating lessons with it--how to rethread it, how to tie on the new thread and pull through, how to do different stitches, change/adjust the tension, etc. If it was bought from a discount store (JoAnn's, Walmart, online, etc.) you will have to search out serger classes to learn how to operate it. Do you have a sewing machine repair place that you can take it to? They might be able to give you some tips in case you are doing something wrong. There are also several good books about sergers you could try. Singer Reference Library Sewing with an Overlock http://www.amazon.com/Sewing-Overloc.../dp/0865732485
would be a good one as your serger is a Singer. ABCs of Serging is another good one. http://www.amazon.com/ABCs-Serging-C.../dp/0801981956
The Ultimate Serger Answer Guide is a great book to troubleshoot serger problems http://www.amazon.com/Ultimate-Serge.../dp/0801986451
For example, when threading a serger, make sure that you thread the loopers first and the needles last. Because the needle threads loop around the lower looper, if you thread that looper after the needles when the thread breaks, the lower looper thread will break when you start to stitch again. That's because the lower looper thread has no where to go because it's trapped by the needle threads.
Your serger could be out of time. If that's the case, you need a trip to a sewing machine repair man. First though, check and make sure that your needles are as far up as they go and they are not even. The left needles is usually up higher than the right needle. Do you have the correct needles in the serger? Some serger require special serger needles. And even if it does take universal sewing needles, some brands might not work. My serger has to have Schmetz needles in it; other brands of needles won't form a seam. And make sure that it is threaded correctly. There is usually a color coded threading guide somewhere on the machine, usually inside the door to the loopers. Also make sure that the threads are inside the tension discs. If they are only laying on the outside of the discs instead of between them, there is no tension on the thread, causing large loops of thread in the stitch.
For tension problems, which tension to change depends on what it happening in the stitch. If the needle threads show loops on the back side of the stitch, they are too loose. Tighten them until they are just dots. If the loopers meet on the back side of the stitch, the upper looper could be loose or the lower looper could be too tight. You will need to experiment to decide which is true. Thread the serger with 4 differenct colors of thread (using the color scheme from the threading guide is a good idea). Start with a long strip of fabric. Fold in half the short width and start stitching. Every couple of inches, change one of the tension dials until that thread looks like the picture in the manual. Change fabric strips and go to the next tension dial. By the time you are done with the 4th strip of fabric, your tensions should be correct. For a stitch used as a seam, the looper threads should meet at the edge of the fabric and the needle threads should just show as dots on the back side of the stitch. When you change the stitches, always start with the recommended tension settings and adjust to your fabric.
After you have exhausted all other avenues, you just might have a lemon of a serger. Then your recourse is to take it back to where you bought it and complain. Start with the manager of the store where it was bought and go up the chain of command from there.
Did you replace both needles?
I've always heard to stay far, far, far away from Singer sergers! They're just no good
If you're able to get another Kenmore has a decent form for just over $200, and brother's cheapest model (under $200) is supposed to be a great machine.
I have a singer, it's an older model. I had a lot of the problems you are describing, I tried fixing it myself and wound up snapping the lower looper. ordered a replacement, problem was still there...
I finally took it to a shop and they made it SING like it's supposed to. basically the loopers had come out of alignment, and I didn't have the manual or specs to know how to align them properly.
All my problems were solved for $40.