This does not sound like an easy problem to fix, since you've wisely tried just about everything already. It sounds like there is too much pressure on the presser foot and too little grip by the feed dogs.
I would check everything in this order:
- feed dogs engaged (up)
- stitch length set; since they've been too small, I would set them at 8 or 10 to the inch
- walking foot properly installed so it lifts as the needle comes up (the little Y bar securely in the bolt that holds the needle in place)
- setting the tension might take some trial and error

If that doesn't work, buy a new machine! :~)) I have 5 machines tho so I'm probably not a good person to give advice about that. "Buy a new machine" ALWAYS seems like a good idea to me.

Kate

Several years back I purchased fabric to try quilting - the idea fascinated me. After struggling with my old machine, I put my project away. A couple of years went by and I was once again inspired to try quilting by a friend who had made such beautiful quilts. I purchased a new machine, in my case, a Janome 6600, and a whole new world opened up to me. Two and a half years later, I'm an avid quilter with thirty projects to my name.

If you can afford it, but a new machine. It will give you a new lease on your quilting life. And if you already do FMQ on your old machines, you will so enjoy your new one. I would suggest one with a harp that is 9 to 11" wide. Let us know what you decide. Good luck.

Have you tried quilting using a regular foot instead of the walking foot? I sometimes have the same problem with the walking foot.

That said, I have 4 machines (trying to keep up with Kate LOL), so I'm not knocking buying a new one, either. There are many on the market that have quilter-specific features.

Donna

Thank you all! You could tell I was leaning towards a new machine, and I think I just wanted some validation, so thanks!
Msmeow-I tried quilting with the regular foot when I first started out and had problems with bunching fabric and also with the tiny stitches. So I tried the generic walking foot with no luck either. While I am shopping for a new machine I might revisit the regular foot though, because I think that I now have a better understanding of feed dogs and pressure (the tension is still mysterious!).
Can you all tell me which of your machines you like best? Loisf has already mentioned her Janome 6600.

Thank you for the suggestions Kate. My walking foot sounds a little different-it just has a straight bar that rests on the needle clamp. Maybe that's why it doesn't work as well. As for tension, if I change it at all I get weird stitches, so I've been leaving it alone.
Loisf-thanks for pointing out the harp measurement. I wasn't aware that machines varied in this way!

Make sure you have completely cleaned and then oiled the machine - with new sewing machine oil - according to the manual's instructions. If the feed dogs are filled with years of lint and fuzz, they will not work properly. Remove the needle plate and make sure it clean. Use the feet that came with the machine to get it stitching properly, before you try to use the walking foot. These old machines are work horses, but they do need to be free of fuzz & old gunky oil, especially if they haven't been used regularly. You may also need to adjust the pressure on the foot. Make sure you are using the correct bobbin (wound properly & inserted correctly) & a new needle.
I also own too many sewing machines from very old to the newest and greatest -- and I seem to prefer the old ones! :~)
I think it is a sickness. So, buy a new one if you want to, so you can enjoy sewing and quilting, but try to get the others working -- a girl needs a few machines for back-up!

I bought my Baby Lock Jane just for free motion and straight quilting. It has a bigger harp than my favorite old Pfaff Tiptronic 6270. I didn't give up my Pfaff though. I piece on it and quilt on the other and I love them both.
LindaB/CA

If you wanted to be enabled, you came to the right place as far as getting a new machine goes!

How are you supporting the bulk of the quilt? If it works OK on small things and not large ones, it could just be that the bulk is pushing against the machine or there is too much drag or pull because of weight and gravity... the only other things I can say are to make sure you go slowly and use a large enough stitch length... and that you aren't alone, it has happened to me too, on all my machines, walking foot or not, and can be frustrating. ..

I only have three machines, 2 computerized and one vintage... but I look and dream about more every day... I am with Kate, getting a new machine is always a good thing! Since you mentioned adjusting the feed dogs, I just want to point out that you may lose that ability in a new machine.... most modern machines don't offer that ability anymore... they are either all the way up or all the way down with nothing in between...

Many modern machines (mostly low end) have also lost the ability to vary presser foot pressure, so be careful when shopping...

However, the new features available are enough to make your head spin:push button thread cutters, knee lifters for the presser foot, needle up down, push button start stop, built in threaders.... A dizzying array to be sure! The push button thread cutter if you get a machine so equipped, will change your life! The only times I use the vintage machine are when I need adjustable feed dogs or when I'm feeling nostalgic!

good luck and let us know what you decide!

Thank you all for the suggestions! I am going to change the needle, clean out the fuzz, and try quilting on my kitchen table to support the weight of the quilt. Even if I do decide to get a new machine it will take me a while to research and think about features and shop and in the meantime I can keep trying with the old ones.
I'll keep you posted.

Hope you get that worked out. I have found a good deal of my stitch length irregularities worked out when I developed a better support for my work in progress. The weight of a batted quilt has a life of its own and will pull the work in progress and when I started waxing the base of my machine, making sure it was not moving of its own accord from gravity, and learnt to pull my work toward me, instead of shoving it away from me the problem resolved itself. I am sold on the heavy, all metal vintage machines since they do not travel around on you as you work. The machines I use do not have a lot of bells and whistles............that is less important to me than a good machine with shafts and gears and no rubber belts to muck up timing, and a heavy foot pedal I don't have to feel around to find when it travels all over the floor. LOL

I have added a link to what you might need. It does sound to me like you need a bigger surface for the bulk to glide across. I had the same problem with my old Kenmore. Check out this extension table, I learned about it on Bonnie Hunter's site and she highly recommends it for people who have old machines that don't have the quilter's extension surfaces. Even with an extension table, on my new machine I have to make sure that the large quilts aren't hanging over the edge of the sewing area, it will cause that bog down that you are getting. Of course a new machine is a wonderful thing, but with the right stuff the old ones can do a great job.

Here is a link that might be useful: Universal Extension Table

A quick-fix for fabric support IF you have sturdy ironing board: Set up the ironing board beside your dining or kitchen table, about 4 inches lower than the tabletop. Set the sewing machine on the board; lower (or raise) the board until the feed dogs are level with or just slightly above the table top. This gives you the full size of the table to support the fabric. I use a second ironing board on my left, sitting above the machine's board (even with the tabletop), and sometimes even a third board on my right to support the rolled quilt as I feed it through the machine. I bought 6-gauge plastic at JoAnne's to slipcover the ironing board tops -- the fabric just glides right over it!

I used the table+ironing board combo back when I sewed clothing; it works just as well for a quilt as it does for a dress. I've looked at the acrylic tables now available, but I prefer the extended area the combo provides -- 2 square feet of acrylic just isn't big enough when you're maneuvering a king-size quilt!

Thank you for the link ritaweeda-that is definitely more affordable than a new machine. Although I have done some research online and the Brother PQ1500 is very tempting!
Meldy_nva your idea is ingenious! I think it might work for the kenmore but the penncrest machine is so heavy I'm sure it would collapse my ironing board.
Thanks again to everyone for the suggestions. Once I get some time to try them out I will be back to let you know what works.

It sounds like you have gotten your money's worth out of your current machines, so it might be nice to check out a newer machine.