I have a Janome 6500. To make sure I have a proper 1/4" seam. I used one of my rulers and green/blue painters tape (masking). Put the needle down, slide ruler under the foot against the needle, put foot back down. Then put the tape down right next to the ruler. This will be the stitching line. Pull out the ruler, now draw a 1/4" line on the tape. Plus I double check that this line lines up with the little dashes on the on the bobbin plastic plate (but do not put it on the plate). The reason I do it this way and not put the tape as my 1/4" seam area, is 1) it is easier to see the black line, 2) it also doubles when I have to sew HST (I do not have to draw line on each piece) I just line up the point of the HST and sew.
Another thing that I did was just tweaked (bent ever so slightly) the guard on my 1/4 foot. Plus when sewing, my fabric just feather touches the guard, not hard against it.