I am sewing a knit fabric on my Lily 540 and it is skipping stitches like crazy. I have tried adjusting the tension and the stitch length with no success. seem to always have a hard time with getting even stitches on knits... any solution?

When sewing from thick to thin layers, it is common for industrial sewing machines to skip stitches or produce uneven stitches. Here are some things you can try to prevent this issue:

1. Use the right needle: A needle that is too small or too large for the fabric can cause skipped stitches. Make sure you are using the correct needle size and type for the fabric you are working with.
2. Adjust the presser foot pressure: The pressure of the presser foot can be adjusted on most industrial sewing machines. Decrease the pressure of the presser foot when sewing over thinner layers to help prevent skipped stitches.
3. Use a walking foot: A walking foot can help prevent skipped stitches when sewing over multiple layers of fabric. The walking foot will help feed the fabric through the machine evenly, preventing skipped stitches.
4. Adjust the tension: If the tension is too loose or too tight, it can cause skipped stitches. Adjust the tension according to the fabric you are working with.
5. Use a stabilizer: When sewing over thin fabrics, use a stabilizer to prevent the fabric from puckering and causing skipped stitches.

If none of these solutions work, you may need to take the machine to a professional for further inspection and adjustment.

Are you using a brand new ball-point needle?

Basic Maintenance Tension Skipped Stitches

here is a link for a free manual for the machine, it should have the information you need in it,, always use a scrap piece of fabric your sewing to adjust the tension, when adjusting the top thread tension do it one number or letter at a time and then sew on the scrap fabric, until you get the desired stitch you want.

http://www.singerco.com/uploads/download/617_7258-instruction-manual.pdf

Needle types
There are three main types of needles that are used for the majority of sewing, as well as many specialty needles.
Universal needles have a slightly rounded tip, and this general purpose needle should be used on wovens as well as some sturdy knits.
Jersey needles have a medium ballpoint tip designed especially for knit fabrics because it slips between the knit fibers and does not break or damage them while sewing.
Stretch needles, often confused with Jersey needles, are also a medium ballpoint tip, but these have a special eye and scarf that are designed for extremely stretchy fabrics and elastic. Swimwear is an ideal application for this type of needle.

Most likely the timing needs to be adjusted. Try to do straight stitches on the left and then on the right. Does one skip but not the other? If so; get it timed.

Most sewing machines will sew well on sturdy woven fabrics without being perfectly adjusted. However, because knit fabrics have more stretch, and have a tendency to pull the needle in one direction or another, a sewing machine has to be very well adjusted to sew on them well. You needle clearance or timing could be slightly off, and would cause the machine to skip on knits. Unless you have a reasonable amount of experience with adjusting sewing machines, it would probably be best to take your machine to a repair shop to get it adjusted. Make sure you tell them what kind of thread and material you are working with. Take some samples if you can.

Skipped stitches
1. A bent or dull needle
2. The wrong needle for your fabric
knit fabrics require a jersey or ballpoint tip. Most wovens do well with a universal tip, and specialty fibers, like leather or metallic, usually require specific needles.
3. Incorrect machine threading
4. Unbalanced needle thread tension
Start by making relatively small changes and run a test stitch to evaluate the impact. If you need to adjust the tension dial using woven cotton fabric with good quality all-purpose thread and a new needle
5.check the needle is inserted correctly. The needle needs to be pushed as far up the needle shaft as possible. It's easy to insert the needle half way, clamp it down and think it is inserted correctly.
the flat part of the needle should be positioned towards the back. If the needle is not inserted correctly, it will not be able to pull up the bobbin thread and will cause skipped stitches.
6. If the suggestions don't help then it is time for a tune-up.

Lower the pressure on the feed dogs, use a stretch stitch, and longer stitch length. Be sure to use a good quality thread, and maybe go lighter weight thread.

Not sure if I can help, but it may have to do with the heavy thread as well as the fabric and needle combination. If the fabric is thick or tightly woven, be sure to use a brand new sharp needle. (If the fabric is tightly woven (like Batik), a thicker thread may present a problem.) In your case, if using a heavier thread, perhaps a top-stitch needle would be beneficial since it has a bigger scarf to protect the thread. With the heavier thread in the top, the top tension will need to loosened. BUT, if you loaded the heavier thread in the bobbin, the bobbin tension will need to be adjusted to accommodate the thread thickness. However, remember that if you adjust the bobbin tension for this project, you will most likely need to readjust it for the next project using different materials.

FWIW, if the machine still works fine with regular fabric and thread, then you'll know that the issues revolve around the current project.

Understanding Thread Tension Threads

How to Achieve Ideal Sewing Machine Thread Tension Threads

Sewing Lesson 10 How to Fix Tension on Your Sewing Machine

Never mess with the bobin tension, just make an adjustment to your stitch length, I suspect the stitch length is set for small stitch, try it on #3

You can adjust the pressure foot(not footpedal)which puts the prsure on the foot by the needle. Also try altering the stitch length. If the stitches are skipping on silky fabric or knitted fabrics try using tissue and sewing onto that directly then tearing it off afterwards.