I FMQ on a Juki TL98QE, I have it in a table. FMQ on it almost all the time. Beautiful stitch and as good as I am. If the Kenmore does a better job, that is what I would use.

No worries! That doesn't sound like a tantrum. It's frustrating when your equipment doesn't work the way you want it to / it should.

Is the Janome recessed into its own table, or do you have it on a table and things built up around it? Trying to think of a way to make the Kenmore more convenient.

I found thread makes the difference. I do find that I have the best luck with Gutterman when FMQ'ing. I think if I was better about knowing more about tension I could use other threads with same results. I also found the gene white washer works really well.

machines can be very picky about what thread / needle combos they like and do not like. We have 4 different machines in our house ( I am not the only one that uses them LOL ) and each and every one of them have different preferences for needles and thread. Try a bunch of different thread / needle combos to see what works for yours ! It does not have to be expensive to find out, you only need a small spool of each brand to test with on some small scrap sandwiches until you find what works best, it saves on buying a large cone of thread only to find out your machine hates it. Also, I know this goes against most of what has been heard, my Brother PQ-1500s has NO problems with different threads from top to bobbin. On alot of projects I use surger thread in the bobbin and Essential Threads from Connecting Threads on top. Just play around with your machine and try the unheard of !

Switched to an 80/12 needle and at first though it was a little improved, but no, not really. So I moved my thread and bobbin over to the Kenmore. My top stitches are beautiful. Took a little jiggering with the top tension. I went from 4 down to 1 1/2 on that and no more bottom thread dots on top. Absolutely no eye lashing on the bottom regardless of the top tension. I may try to finish this quilt on the Kenmore. I'll have to move things around and get some tables situated to support the weight of the quilt but that can be done. I'm just so tired of fighting with the Janome and so disappointed. Guess I thought it would be a dream come true. More like a nightmare! May call the dealer in the morning & talk to them; maybe they can help me sort things out with the Janome.

https://www.superiorthreads.com/medi...guide-home.pdf
This is the best reference for Superior threads especially, but even a great starting point for most thread / needle / tension combinations.

I'm not familiar with the Janome, which way is the bobbin oriented? Horizontally or Vertically? Horizontal (according to SM shop I talked with) requires higher tension for FMQ than the Vertical, but it shouldn't be astronomically higher... it should be possible to balance the tensions. 98.9% of my FMQ to date has been on vertical bobbins

If it was me I would take my machine to the dealer and let them adjust it.
Then you will know what tension, needle, thread combination works best
on your machine. Sewing machines can be so temperamental sometimes.
Hope you can solve this problem soon. I feel your pain.

I have the very same "top thread showing on bottom" with my Janome. Mine is a very inexpensive Janome 415 model that I bought to carry around. The tension on the stitches has been an issue forever. had the darn thing in the dealer numerous times. Just got it back, did about 50 inches x12 inches free motion on a quilt and the bottom thread was already getting loose. I have changed threads, slowed down, used different stitch lengths, and no better results. I'LL NEVER BUY ANOTHER JANOME, nor will I ever recommend one either. My old 1967 Singer is a consistent machine. BUT the feed dogs don't drop. I'm working on figuring out a way to do my FMQ on that machine. The tension is good even if I don't get it serviced but every 10 yrs.. literally.... Keep taking your machine in with examples and see if they can fix it. OR replace the machine as a lemon....

Your dogs don't need to drop. Set the stitch length to 0 and quilt. What model? Leah Day doesn't drop her dogs.

What happens on the Janomes if you tighten the bobbin tension a smidge? Like 1/16th of a turn to maybe an 1/8th?

I haven't touched the bobbin tension. The "blue dot" bobbin case is a separate case allegedly designed just for fmq. Supposedly you wouldn't have to adjust it. The bobbin is a horizontal drop-in bobbin. On the Kenmore it's vertical & think I've read somewhere that's supposed to be better for fmq.

Tuckyquilter, my Kenmore came with a little plastic darning plate to cover the feed dogs. I think I've read that you can cover them with a card or something too.