Kenmore 1941 sewing machine irregular stitches

What is the stitch length for a basting stitch?

Basting a Seam for Fitting:

At the sewing machine, set the stitch length to 5mm. This will make it easy to remove any unwanted stitches. Sew the seam at the desired seam allowance. After fitting and the adjustments have been made, sew the seam with a normal stitch length of 2.4mm.

Sewing Basics - Basting - Janome

and also related to Brother

https://www.google.com/search?q=Brother+XL+3500+Basting+Stitches

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Try this:
Remove the top thread completely from the machine.
ALWAYS RAISE the presser foot and rethread from the beginning.
Verify the thread is following the correct threadpath.

FWIW, stitch length 7 is pretty long. Are you running a basting stitch?

Unable to locate a manual for the machine you listed. However, you can usually make your own basting stitch by setting the stitch length as long as possible, stitch width to zero, and loosen the top tension.

A baste stitch is basically setting the machine to a straight stitch with the longest stitch length available. Loosen the top tension slightly if you want to remove the basting later.

Here's a manual for your machine:

ELNA eXcellence 730 Instruction Manual

If your machine does not have a "basting" stitch selection, you make your own basting stitch by:

* Setting the stitch length to the maximum
* Loosen the upper tension so the bobbin thread lies flat under the fabric

Then to gather or remove the basting stitch, it is easy to pull on the bobbin thread.

To baste, set the stitch length as high as possible (zero is a non-stitch length, probably 4 or 5 on your machine is the largest stitch length). Set the stitch width to zero so there is no zig-zag.

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the stitch length is governed by the cam action connected to the walking foot
that means that the stitch length is governed by the amount of material that is pulled through in the period of time that the needle comes up and goes down
normally the cam action is set by the stitch length lever/ reverse lever
if there is a necessity for a longer stitch, the cam would have to be changed on the drive shaft underneath
That will require a discussion with a sewing machine mechanic to determine if there are cams or other linkages that can be fitted to alter the stitch length for the manufactured maximum

if the machine can do a basting stitch the information should be in the sewing machine manual, if you don't have a manual, add a comment with the name and model number of the machine and someone should be able to help you find one.

or you can also try youtube for a video

Some machines have a built-in basting stitch. If yours doesn't have it, the closest you can get is setting the stitch length to as long as possible. To make the basting stitch easy to remove, loosen the upper tension. Then to remove the thread, just grab the bobbin thread and pull.

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Basting is simply using a long stitch that can be pulled out after you put the main stitch in. It holds fabric in the right place till it is sewn.