Brother serger slows down

Don't expect a quilt to be as accurate from a serger as from a sewing machine. First, you probably want to focus a strip quilt where rows of strips are stitched together. If you do strips, you won't have to worry so much about maintaining an exact 1/4" seam. You can also vary the widths of strips in order to camouflage any seam variations. Avoid a pattern that requires points being aligned! Any seam width variances will not as obvious as an error (it is intensive getting an accurate 1/4" on a sewing machine--so-o-o-o much more difficult on a serger). There are usually seam width marks on a serger that you can follow as a guide, but straight line serging is very difficult to accomplish. You can always try marking a line on your serger using painter's tape.

FWIW, making a strip quilt on a serger is a fast way of finishing a quilt. I divide my quilt into 3 or 4 sections, like making it in thirds or fourths. That way, when the quilt begins to grow, you are not constantly grappling with flipping or turning the heavy and bulky fabric. Instead, do each section separately, then stitch the sections together to make the whole quilt.

Also, be sure to press all the seams of a strip quilt in the same direction.

Strip Quilt Patterns

4 Free Strip Quilt Patterns That Standout from the Crowd Fons Porter

How To Sew An Easy Strip Quilt

https://www.quiltinaday.com/community/topic.asp?forum=2&topic=5481

Make FAST Serger Strip Quilt with 1 4 square Triangles

If machine speed is not controllable with your foot controller, you probably need a new controller. These items should be covered by a 2 year warranty from Janome.

maybe knife is too big for the serger.

Call your local service shop. Baby Locks in closets for years usually have this problem The manual recommends annual maintenance by a pro, and they will oil the internal lobes of the feed dog apparatus. It cannot be oiled from the outside, nor with covers off, but must be taken apart. If those lobes lose the oil and heat up you will feel "surging" then slowing repeatedly -- fast then slow then fast etc -- until the lobes over heat and sort of weld themselves to that small barrel looking case. So a Baby Lock can sew, then temporarily be sluggish then later slow till sluggish; and at worst, seem to be doing everything right BUT not advancing the cloth -- that's when the worst damage is done and professional repair is needed. In PA might cost $150 to fix. $70 in parts; $80 in labor (2012 prices)
Been there, done that.

may need cleaning. you should have it serviced

Perhaps was same as my problem.

Call your local service shop. Baby Locks in closets for years often have this problem The manual recommends annual maintenance by a pro, and they will oil the internal lobes of the feed dog apparatus. It cannot be oiled from the outside, nor with covers off, but must be taken apart. If those lobes lose the oil and heat up you will feel "surging" then slowing repeatedly -- fast then slow then fast etc -- until the lobes over heat and sort of weld themselves to that small barrel looking case. So a Baby Lock can sew, then temporarily be sluggish then later slow till sluggish; and at worst, seem to be doing everything right BUT not advancing the cloth -- that's when the worst damage is done and professional repair is needed. In PA might cost $150 to fix. $70 in parts; $80 in labor (2012 prices)
Been there, done that.

You can download a free manual at the Brother website http://www.brother-usa.com/ModelDocuments/Consumer/Users%20Manual/UM_1034D_ENES_178.PDF

Your problem is probably the stitch length adjustment cam (located on the left side of the machine) To fix this problem you will need to remove the small plastic cap (with red arrow) covering the screw securing the cam. It is usually also necessary to remove the connecting rod/sleeve that the cam rides in. Once both of these parts have been removed, you will need to carefully separate them and resurface the inside of the sleeve. This can be done with a very fine (500grit or higher) emery paper. Once the cam fits inside the sleeve without binding, reassemble using sewing machine oil or lithium grease and adjust feed dog timing.

If you go on YouTube and key in Brother serger 1034d threading they show you all kinds of good stuff. How to thread it, how to use different feet and the different stitches you can make.

Find a sew & vac shop near your house they usually have sewing machine parts