Ricarr Sewing machine model 555SU. It's not

This video may help. Probably not your model, but machines tend to thread and operate similarly.

How to Thread Janome Sewing Machine

here's my suggestions
change the needle-make sure the needle is inserted correctly
into the needle holder & also turned the right way
make sure when sewing on the machine that the top thread does
not come off the thread take up lever
check the top thread tension it may be too tight,, usually 4 is good
or if the machine has automatic tension set it there
make sure it's the right needle for the machine & make sure it's the
right needle for the fabric & thread.
some thread is knotty ,,, make sure the thread is good quality

Grab some scrap fabric of the same type you'll be sewing. Tighten your top tension and test sew until you see until you see the top thread of a seam go like a straight line and the bobbin thread loops on top of the seam. Then back off of the top tension until those loops disappear.

If you never see it the top thread go like a straight line... your top tension needs to be cleaned... and make sure you have the pressure foot UP when you thread the upper thread.

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.

Things to check: 1) is the needle bent? Replace needle. 2) Do you have any lint/dirt in the bobbin case or the race (where the thread catches)? Clean the bobbin case. 3) Make sure that you are using the correct bobbin for your machine and that it is installed correctly. 4) Check that the bobbin case tension is correctly set. (For some machines this is easy. If the bobbin case can be easily removed, hold onto the bobbin thread and dangle the bobbin and bobbin case assembly. Additional thread should not pull through.)

The bobbin case or race may be damaged. Depending on the brand and model, you may find a replacement at your sewing machine dealer or online. If you add a comment with the your machine brand and model, I may be able to provide additional assistance.

Cindy Wells
(make sure you hold onto the top thread and have the presser foot down.)

Hello,

You can take the slide plate off, that your needle goes through and watch to see if the arm grabs the bobbin thread, if you can get it to pick up, than slide scissors or something flat under your needle and manually pull both threads through, replace the plate.

Your bobbin thread could be wound to tight or spliced threads on it, and your tension needs to be adjusted. If your using a pedal, try setting to a slower speed.

I would try a different bobbin and thread it manually as in the step I mentioned, if you can't see the arm grabbing it, you will need to check to see if you have loose threading jammed in youir machine, if this isn't the case and adjusting the tension dosen't help...than you will need to replace the bobbin casing.

Kind regards!

Hello

Set the tension on the sewing machine for the weight of the material you want to sew. The tension setting shows in the stitch on the material. Use the chart on the machine that matches types of stitches with suggested material tensions. An example of this is, the stitch to sew jean material is different than the stitch to sew silk.

Take the bobbin and wind the thread around it. Make sure the bobbin is empty and don't fill it too full of thread. A bobbin filled too full won't stay tightly spun.

Thread the string evenly on the bobbin. Move the thread back and forth evenly and in layers that are level. Many Singer sewing machines have a bobbin winder on the top of the sewing machine, and the consistency of how it threads can save you frustration later.

Find the hole on the bobbin that is located near the inside spindle of the bobbin. Take the thread sitting on the sewing machines spool and insert the thread in the hole from inside the bobbin to the outside. Set the threaded bobbin on the spool designated for spinning on the top of the sewing machine for some Singers.

Turn the side drive wheel slowly until the threaded bobbin has a layer or two of thread on it. Push down on the drive peddle and fill the bobbin, but don't thread it to the very edge. If the bobbin is too full the thread will release erratically. Cut the thread from the spool.

Drop the bobbin into the bobbin case under the area where the needle sews the material. Close the case and turn by hand the side wheel drive until the bobbin threads into the sewing machine. You can tell when the bobbin is threaded by the tiny piece of thread that juts out of the bobbin case where the needle goes up and down.

Grab the thread with your fingers and pull it out approximately 4 inches. Your bobbin is now spun and threaded.

Hello

Load your Kenmore sewing machine with the right thread and bobbin thread for your project. If you use the wrong weight thread for your fabric or severely uneven weights of thread, this can cause the appearance of a tension problem when it is, in fact, a thread weight problem or a problem with your sewing speed. If you go too fast, you will break the thread. If you go too slow, you can cause loops. Uneven pressure can cause stitches to vary greatly.

Test your Kenmore sewing machine's tension by sewing on a piece of scrap fabric. If your tension is way off, then test on some basic cotton or a firm blend simply to get your tension right. Do not try to start adjusting your tension on silk or leather. Get a base adjustment on a more standard fabric first.

Look at the top threads and bottoms threads. If the tension is off on one side, it will usually affect the other side slightly. So select the side that looks more maladjusted to start adjusting the tension.

If the top thread is too loose or too tight, you will need to adjust the tension dial. This dial is usually located a few inches above the needle on the Kenmore machine body. Usually, your machine will have markings to indicate which direction tightens the tension. If these have worn off over the years, watch the dial as you turn it. If it appears to move toward the machine body, then it is tightening.

If the bottom thread is too loose or too tight, then you will need to open the door to the bobbin case. On some Kenmore models, there is a little screw near the bobbin case that can be adjusted slightly to adjust the tension. On other Kenmore models, there is a screw on the bobbin case itself--not on the bobbin, but on the bobbin's casing. This will also adjust the bottom thread tension. Adjust the bobbin thread tension to make slight changes.

If the thread is looping severely on one side, the thread weights might be off. For instance, look to see if you have a lightweight thread on the bobbin and a heavyweight one on the top. If the thread keeps breaking, the top tension or bottom tension could be too tight or the thread is too lightweight for the material you have selected. Check your combination of threads and material. Also make sure you are using the right weight needle and the right foot for the sewing step or project you are working on.

If your Kenmore sewing machine's tension is off severely or if you have not used your Kenmore in a long time, then you might need to take your machine in to be serviced. Sometimes, the inner parts need to be oiled or the entire machine might need to be cleaned and calibrated by a professional. If you sew a great deal or if your machine sits idle a lot, both situations will usually require some servicing to keep your Kenmore sewing machine and its tension in perfect working condition.

check that the bobbin thread is pulled thru 'the tongue' of the bobbin case: that is what controls general tension of the lower thread. also make sure the upper thread is threaded thru the tension disk and the disk is 'grabbing it'.

Make sure your bobbin thread is turning clockwise as it sits in the bobbin case. There is a screw on the outside of the bobbin case you can turn with your thumb slightly to adjust tension. If you dangle the case from the thread and give it a light ****, it should move down slightly when doing so-an indicator of good bobbin tension.