What model is the Kenmore? A lot of people swear by them, and I have several (6 sort of counts as several) and they all sew quite well, and they are usually easy to work on. The ones I have are on my give-away list, as most were given to me by people who said, "This machine just won't sew." With a little cleaning and oiling, and adjusting the tension, the machine will produce a little lap quilt for me, so I can show the person who I gift it to that it sews. I think the bottom tensions must tighten themselves up, because that is usually a first place to adjust.
Also, Charlee, I used your idea of the o-rings for a sewing machine belt for a White 1099 Jeans Machine. My OSMG said it was a good machine, but would have to order a belt. I said let me see what I can work up first. I had gotten it at a yard sale for $5. It has all the accessories, including a hopping quilting foot that is different than the one I have. The White one has a bigger opening than the one that was with my Pfaff 230 and is easier to see what you are doing. It is a pretty cool machine. Also on the "williing to let someone borrow" list, but I may keep the hopping foot. The man at the farm supply where I got the o-ring was amazed, to say the least, when I told him what it was for. Then he said, I have worked here for 40 years, and never thought of doing that, and my own mama needs a belt for hers and was going to bring her old one in to measure. I gave credit to a QB friend from the PNW.