Some of you will be horrified by my "fix" to get a perfect scant 1/4". I got out a small quilting ruler, put my 1/4" foot on, and moved the needle to exactly where it needs to be, then took a sharpie permanent marker and drew a line straight to the front edge of my machine AND the extension table. Now I get the same seam every time and I have quit watching the needle, which was probably part of making my original bad seams......

I use Bonnie Hunter's method and it works really great!!! Now I can get a scant 1/4" seam on all my machines.

I have a Janome and love it. I have had 3 of them. On my machine the setting is Mode 2 #39 and two clicks (positions) to the right for a scant 1/4" seam. Save it in the memory. I also use a 2.2 stitch setting. Mode 2 #39 is the Patchwork Piecing Stitch. With this setting I use a 1/4" foot specially made for a Janome.

I found that Piecing stitch just the other day. But I have to move the needle as far right as it will go to the 9. And with the 1/4 inch foot I'm getting a regular 1/4 inch seam allowance. If I use that clear open toe foot and run the cloth along the edge it's scant. But it doesn't seem to feed all that well. Is it possible something is wrong with the machine?
It's good to hear from someone that has a Janome. When you mentioned the Modes, etc. I know what you're talking about.
Also, how do you save in memory?
As you've probably figured out, I haven't had any instruction on the machine. I bought from a place that has no "after the sale customer service".

Using Acufeed, straight stitch plate and the 1/4 foot with the guide on the side, I found that DF95S (8.3) setting gives and accurate 1/4 seam. However, to get a scant 1/4 I move the needle to the right to the 9.0 setting.

On my Bernina 440 I finally discovered a scant 1/4" seam is two clicks right and line the fabric with the edge of the #1 foot (the basic zig zag foot). On my Featherweight, I have to use a seam guide. I got a large plexiglass seam guide from https://www.novamontgomery.com/shop/...ight-Guide.htm. There are other similar guides at different places. It works great. Since I alternate between the two machines, I use a seam from the Bernina as a placement guide for the Featherweight. The adjustable guide is the only way I get seams that are exactly the same size on both machines.

To test the performance of your machine, how about drawing the sewing line you NEED on a scrap piece and sewing the seam on the line, then press the seam. Measure at that point and see what's what.

This would work - I also use the "index" or "graph paper" method to "find" my 1/4 inch seam.