Tons of loops on bottom

Make sure your presser foot is in the up position before you thread the machine. Dull, bent needles will cause stitching problems, can make the machine work harder, or can damage the machine or your fabric so change the needles often; some say after two medium size projects. Dull needles can make a plucking noise so listen to the noise your machine makes right after you put in a new needle. Make it a habit to listen to the needle noise as you sew also. Dull needles make a "plucking" noise. Check to make sure the top thread is engaged between the two tension disks and that there are no fuzzies in the tension disk or bobbin/ throat plate areas. Make sure the thread and needle are compatable. Refer to your sewing machine manual or find an online chart that references your thread to the proper needle type, size and the proper fabric types that work best. Use the same thread in both top and bobbin. Completely remove your thread and try another thread - top and bottom. 100% polyester thread is some times problematic. Some machines won't sew with certain threads. If nothing worked, you will probably need to adjust the top tension knob. There are some good youtube videos. Look for one with a higher number of views. Loops under the fabric means you need to tighten the top tension (turn knob to right) gradually until you get a proper stitch. Most experienced sewers do not like to adjust the bottom tension screw on the bobbin case if it can be avoided. Bad things can happen if the screw pops out :( !!! I have a friend who sewed all her own clothes in 4-H, high school, college, and many of her children's clothes. After about 40 years of sewing and properly maintaining her machine, I received a call from her because nothing she did worked to get her machine to sew a good stitch. She had no idea there is a bottom tension adjustment on the bobbin case. One last time...do not adjust the bobbin case tension unless you know what you are doing. The screw should never be unscrewed so that it pops out. It will often not go back in correctly. Some some sewing machine repairmen/women can rebuild the bobbin case if the screw is still good. A new authentic bobbin case from the manufacturer can be pricey. One of the most common problems are tension problems. Do not let children or inexperienced adults mess with your knobs. There are youtube vides that address just the bottom bobbin case tension adjustments. If you are working on an important project, write down the type of fabric and thread you are using, stitch length and width settings, and the number setting on your tension knob. Or you can take a picture of it on your phone. This is even more important for sergers. I also record this information for appliqu? stitches, top stitches and quilting stitches (etc.) and keep it with the pattern envelop so if I make the project again, I have a starting place and save time and frustration. I hope this helps you.

We all know that proper threading makes for happy sewing machines and happy stitchers. And while we emphasize threading with your presser foot up- there are a few other things to keep in mind while threading your machine to make sure your sewing time is happy time!
Have you ever been sewing along on a project, decided to change threads, and all of a sudden you hear a THUNK CLUNK THUNK when you start sewing again?
If not, good for you. But I know that this has happened to a lot of our customers for sure!
Often, this sound comes from not getting your thread in the take-up lever while threading.
If you have a new needle that is the appropriate size/type and your machine is clean, but you start to hear a clunking sound after rethreading, this is the first thing to check. And it's such an easy fix. In fact, I think some people are so surprised when we tell them to simply rethread, because the sound is so terrible they think something is seriously wrong with their machine.
Now, there could be something really wrong with your machine, but the biggest clue that it's a missed take-up lever is that the problem starts suddenly, most of the time after rethreading. (machine was sewing just fine before that).
How do you make sure to thread your take-up lever?
On some machines, it's very easy to see the take up lever, and on others it's hidden behind the machine casing. Here's what you should do to try and ensure success.
-Raise your presser foot!(Full rant here)
-Put your needle in the highest position (use the needle up down button or line up the notch on your handwheel with the casing of your machine- more info here)
-Clear the thread path. Make sure there's no thread wrapped around a spool cap or trapped under your spool.
-Feel it! If your presser foot is up and your needle in the highest position, hold the thread near the spool with your right hand and thread with your left, you'll be able to feel the thread slide into the take-up lever.
-STOP immediately if you hear a THUNKing sound and re-thread. What's happening is that your top thread is not regulated, and it can ball up undereath the feed dogs and cause issues.
-Clean out your bobbin area and re-thread if you think you missed your take up lever.

have you tried changing the needle?
have you tried adjusting the top thread tension?
it might be the needle and the thread are not compatable,, the needle may be to light for the thread.
if the suggestions don't help, sew on the sewing machine till it makes the loop and then stop the machine and take it to the repair man and let him see the loop and then ask him why it's making the loop.

Loops appear on the surface (top side) of the fabric?
Reduce the tension by turning the upper tension control dial to a lower number. If the loops still appear on the surface of the fabric after you adjust the upper tension, the bobbin thread may be too loose. In this case, turn the screw clockwise, being careful not to over-tighten the screw, approximately 30-45 degrees to increase bobbin tension. After you adjust the bobbin thread, adjust the upper thread to match the bobbin thread.
Make sure you reset before your next project.

here is a link for a manual for the machine
http://ifixmachines.com/index.php?page=shop.product_details&flypage=&product_id=1540&category_id=1575&option=com_virtuemart&Itemid=54&vmcchk=1&Itemid=54

try changing the needle--use one that is correct for the fabric being
sewed
the top tension adjustment for the bottom loops
make sure the bobbin is turned the right way in the bobbin case
make sure the top thread has not come off the thread take up lever

If by "bobbin thread is usually too loose." you mean that you are seeing loopy stuff on top of your seam... then first you need to make sure your bobbin is un-spooling in the correct direction.

Also make sure that the tension spring on your bobbin case is not missing it's screw. Don't mess with the tension there yet... loosen your top tension first... sew on scrap fabric of the same type as your project. Loosen the top tension until you stop seeing loops on top of your seam. If you have loosened it enough to see loops on the bottom... tighten it a bit.

If all else fails make sure you re-thread the top thread with the pressure foot up position so you make sure you are getting the top thread in the tension discs and try test sewing again.

Take it to an authorized dealer for evaluation.
Find the nearest dealer at http://webservices.us.vsmgroup.com/DealerLocator.aspx?Brand=Viking

This is a top tension issue, you need to check two things,

-make sure you thread the machine with the pressure foot up ( this allows the tension discs to open up so you can pull the fabric away from the machine with the foot up and allows the thread to get to bottom of the tension discs)

-make sure your tension settings are set to the medium setting. (Usually 4 or 5)

If this still does not help, then turn the top tension knob up (from 5 to 6,7,8,9....)

-If that still doesn't do it, your probably need the tensions reset, and your local family sewing store will be able to assist you further.

-Chris

FYI---- Loops on the bottom-- problem is in the threading..
Loops on the top--- problem is with the bobbin.

You have no top tension. Rethread the top of the machine. Make shure you raise the presserfoot before threading.