How do I get a narrower width?

Hello,
Please, make sure the paper is well aligned and there are no gaps between side guides and the paper in the tray. If the paper is correctly positioned in the paper tray, probably your paper width sensor is not working - full with toner, displaced, disconnected or faulty. The paper passes trough the printer, but the sensor does not report the expected width for letter paper and the printer assumes it is A4 or other with less width than letter. The sensor is a plastic flag on a spring passing between optocoupler. Below the toner cartridge there is a rectangular metal paper guide with a narrow cutout on the far right. The flag's arm should be inside the cutout. Check if it's not blocked. It should be rotating freely in paper movement direction and the spring should get it back in vertical position. The optocoupler is right below the flag, but is accessible from below, after removing the High Voltage Power Supply PCB.

They run true to size for length. There are icons on the sole that tell you the width. A filled in icon is medium width snd an outlined foot shows narrow and wide.

There are lots of different wheel sizes on bikes today (20", 24", 26", 700c, etc.), and lot of different tire widths for all those different wheel sizes. Fortunately, tires are marked with their size, so you just need to learn how to read those markings, and they are not complicated.

For the purpose of picking a replacement tube, there are just two numbers you need to know: tire diameter and tire width. These numbers are always written somewhere on the side of each tire. (Sometimes when tires get old the numbers are hard to see. Don't give up, just keep looking.) Here are some examples of what the numbers might say: 26×1.95, 700c x 25. Sometimes the there will be three numbers, something like this: 26×1-1/2×1-3/4. Don't worry about that, just remember the first number (26 in this example), and the larger of the other numbers (1-3/4 in this case). Sometimes there will be letters with the size (such as EA3 or S-6). Sometimes there will be another number or two in parentheses, for example (622) or (559-45). Don't worry about those letters and numbers. They are important for getting a replacement tire that fits, but not important for replacing the tube.

The numbers can be hard to remember. It's a good strategy to write them down somewhere to bring with you.

You have the settinigs on the printer wrong. There are two things you need to do:
1. Open the tray and check that the paper guides are set to 8.5 x 11 (letter). There are both length and width guides in the paper tray, and EXEC size is quite a bit off from letter-it is more than 0.5 inch narrower than letter. It is also shorter than letter.
2. On the printer, use the settings button to navigate to the paper size. (The exact wording may vary; it's been a while since I worked on a 4050. It may be under print settings.) Once you find the paper size menu, configure tray 2-yes, I'm sure-to use letter size, any type. By the way, on HP lasers, tray 1 is the fold down tray on the front, tray 2 is the tray that will hold 500 sheets of paper and is the "drawer" that you load. Don't ask me why they use that numbering system.

there are generally two variable controls .. one adjusts the stitch length (distance between stitches measured in stitches per inch) ... the second is stitch width .. that adjusts how far the zigzag moves left and right .. thats usually just a number from 0 to 10 or so .. 10 would be maximum width .. 0 would be used for straight stitch ..
so you need to adjust the stitch width control to make the stitching narrower .. the controls are called different things on different brand sewing machines .. if you have the brand and model number then there may be instruction booklets available ...

8 or Smaller Board Width 24cm or less (Narrow) 8.5 - 10.5 Board Width 24 - 26cm (Regular) 10.5 or Larger Board Width 26cm or More (Wide)