Is it o.k. to use heavy duty thread on the top and regular thread in the bobbin? Also, I went to the address you reccomended for a manual but the url could not be located?

Be sure the bobbin winding spindle is full to the left.

You may need to clean/oil the machine.

http://www.menwhosew.com/how-to-clean-and-oil-the-singer-heavy-duty-sewing-machines/

Do you mean the Singer 4411 Heavy Duty sewing machine? If so,
first place the spool on the spool pin with an appropriate sized spool holder, if you are starting the project. Snap the thread into the thread guide to the left of the of the spool pin. Wrap the thread clockwise around the bobbin winder tension discs (slightly to the left and forward of the thread guide). Bring thread towards the bobbin spindle. Thread the bobbin (put the thread through the hole in the bobbin). Place the bobbin on the spindle with the hole up. Move the bobbin spindle to the right. Hold onto the thread above the bobbin and step on the foot control pedal. When the bobbin finishes winding the thread, cut the thread at the top of the bobbin and the incoming thread from the spool. Move the bobbin spindle to the left and remove the bobbin. If you have already threaded the machine for sewing, you will need to remove it from the various guides and tension discs that are used in sewing. Then after winding the bobbin, re-thread the top thread.

The directions to wind the bobbin are in the manual on page 12 (page 19 of the PDF). You can find many Singer manuals at the Singer support page: https://www.singer.com/support . The 4411 support page is https://www.singer.com/search/support?lp=support&title=4411 . The current link to the manual is https://www.singer.com/sites/default/files/product_manual/SINGER%204411%20Heavy%20Duty%20Sewing%20Machine.pdf .

I hope this helps.

Cindy Wells

Here's a link to the manual for the machine. You should find your answer there.
Singer Sewing Machine User Manual ManualsOnline com

If you've threaded the bobbin per instructions... then make sure your needle isn't damaged, bent, or dull. Also make sure the needle is seated fully and correctly oriented into the needle bar.

Put a felt spool pin holder (an extra one comes with machine and it's either red or white felt with a circle cut out of it in the center)...remove bobbin, set felt circle in bobbin case to keep bobbin from wiggling. The back and forth motion is knocking the thread out causing it to lay flat against top of the bobbin when you start machine, but felt puts bobbin in correct position! Make sure thread falls into tension slots and carefully pull thread back to left of silver piece (stitch finger). Pull up your bobbin thread. Put in new needle since "bird nesting" or jam may have bent the one previously used. Now it should purr like a kitten...smooth sailing! This is how I fixed my Singer Heavy Duty 4423 when I realized the problem is that the bobbin case is a bit wide and felt takes up slack, raising bobbin also to keep bobbin thread moving smoothly through so it doesn't jump out of tension and rest on top of bobbin!!! Works now!
Jimmy

As a general rule, domestic machines don't like buttonhole twist, that heavy yellow thread you see on the RTW jeans. Sometimes you can put it through the bobbin but use a regular weight thread on top but this means sewing upside down as you'll want the yellow on top. And lots of machines dont like different weight thread top and bottom so it just makes for awful stitching anyway.

Best solution to top stitch jeans is use a regular weight thread, large size jeans needle but thread up two spools of thread on the top with both threads going through the same needle eye. It still may not solve the problem though.

To your machine, firstly change the needle as it may be bent. Then unthread the machine and manually turn the flywheel through a stitch cycle and listen carefully, if you still hear a noise as the needle touches the rotary hook, you've knocked the timing out. Service man visit time.

Probably if you check the manual, it will say 50 weight thread, and you'll need to stick with that in the future.

Those big industrial sewing machines that they top sew jeans on are very different to a domestic SM, many make a chain stitch or fell the jeans seams and are very heavy duty.

Why are you using #16 needle, that is very heavy duty? Did your machine pick up the bobbin thread correctly? Try a different needle, #11, (inserted facing away from you) is usually good. Make sure that you have decent thread and that it is the same weight top and bottom. Now rethread, with the presser foot up and when you have that done, with the presser foot stiil up, pull top & bottom thread, it should feed smoothly, now with the presser foot down, pull the thread, it should barely move. This usually seats the thread in the tension discs. Put your top tension at 3 and see if that makes a difference.

Ensure the bobbin thread is mounted on correctly and using your right hand turn the gear that makes the needle go up and down until it catches the thread.

I answered this a couple days ago but don't know if it went through. I can sew through 6 or more layers of denim with my 226, no problems at all. In my 30 years in the upholstery business I never had a problem sewing leather, vinyl, canvas or multi-layers of fabric. The 226 Consew, the 111W and 211w Singers I had presented zero problems with heavy fabrics - and I don't consider vinyl "heavy".

You need to first of all check threading. If the machine's threaded wrong you're break thread. Also you need to oil under the bobbin case and the bobbin hook and the rest of the parts as well.
Then, loosen thread tension on top by turning the knurled knob that's on the spring that's holding the tension discs. Also loosen bottom tension on the bobbin case by turning the small, left-most screw on the outside of the bobbin case counter-clockwise. Do both with the presser foot down. Pull the thread(s) out and feel the tension. You should be able to pull the threads out with some little effort. Tighten both a little at a time until you get some tension. Run a couple seams and check where the threads meet in the fabric. They should meet in the center. Also check stitch length. If you're using 92 thread (is should be left twist), you should run the machine at about 6 - 7 stitches/inch. I'm running my machine at 5 - 5 1/2 with #69 nylon bonded, and 6 - 6 1/2 with #11 mono.
One more thing; if tension's too loose at the bobbin or top, the machine will jam in the bobbin and thread will break.
Go to www.consew.com and download a pdf owner's manual for free. You need to click on the 224. That machine, the 225 and 226 are the same.

Sometimes when I need to use heavy thread for top stitching to reinforce a seam that has come undone, I will use the heavy thread on the top and regular thread on the bottom. I haven't tried it the other way around for hemming but I would think it would work. I do not currently have a Bernina.