lakekids,
Let me tell you about a recent tension problem I had with my newly acquired Commodore 15 clone. When I got it there were two parts broken. The spring holding the slide plate on, and the thread check spring on the top tension.
I got a replacement slide plate and spring from Sew-Classic and put them in. The check spring required a bit of reforming due to it being more for Singer 15s than the clones, but nothing I couldn't do. After it was installed and all the tension parts set as per the instructions on TSFR. It wouldn't sew worth a hoot. Top tension problems. Too much tension. The bottom tension was fine, but top just wouldn't loosen up. I had the adjuster run out till it was about to fall off the stem but it was still too tight.
Prior to this I had cleaned the bobbin case, the hook and the rest of the lower assembly and had been sewing with the machine using a face plate from my Edison while waiting for the parts to come in. With the faceplate which also has the top tension on it from the other machine it was sewing beautifully. So I knew the problem was not with the bobbin.
I took the top tension apart several times. It was together correctly. It was clean. And it wasn't working right.
I took it apart one last time and laid all the pieces out in order. And looked at them closer. There was an amber looking coating in the center of the tension disks. Old oil that had varnished. So I tried cleaning that in oil and the oil wouldn't touch it. Then I got the Hoppe's #9 Solvent out and cleaned off the old oil I could not see. Scrubbed all the parts and reassembled the tension again. I set it back were it was, set the bobbin tension where it had been and started to sew.
So far I've used several different types of thread and it's working very good. It was the old varnished oil that I couldn't see that was putting a heavy drag on the thread.
I have had to do this to several machines. Oil gets on the tension parts and over the years turns hard and varnishes then grabs the thread when you try to use the machine. I've tried several cleaners including sewing machine oil, Tri-Flow, and others. Some work but the Hoppe's #9 works the best because that is exactly what it is made to do.
My suggestion is to take the tension unit out of the machine, disassemble it, and clean it in Hoppe's #9 with a toothbrush. Then wipe it off, do not oil it (Hoppe's #9 is mostly kerosene), put it back together and try it.
Joe