I received this Japanese Singer 128 clone back here:
https://www.quiltingboard.com/vbulle...e-t316702.html
And when I first looked at it I was shocked at how clean it was, almost as though it had not been used. I started clean up, and there was only the smallest bit of lint under the needle plate. Clean up was quick, including the motor (curiously though I did find a wooden toothpick inside the motor casing).
Time for testing and it sewed great stitches...at slower speeds. If I stepped on the gas it skipped stitches terribly. I had a similar problem on a different machine back here:
https://www.quiltingboard.com/vbulle...s-t312722.html
And so I followed all those tips. I found some oily lint under the shuttle leaf spring and assumed that was the problem, until I ran it again with the same results. After scratching my head for awhile, walking away and coming back 5 or 6 times, I looked at the shuttle while in the machine and realized it was extremely loose in the carrier, flopping around loose. I tried bending up a small, flat piece of metal on the carrier positioned on the underside of the shuttle...and promptly broke it off. It turns out there is a screw on the underside of the machine that holds the shuttle carrier, and which allows the carrier to be adjusted. I snugged up the shuttle and tested again. Success! Even at full throttle (although the machine itself and the case were vibrating all over the place)!
I am guessing the shuttle was this way from the factory, which if so might explain why the machine looked unused, even though it’s probably from the 1950s or so.
There is a paddle lever over under the hand wheel which controls stitch length, and the machine back tacks as well. I wish there where some markings. There’s a knob right there locked in place with the set screw visible in the picture. I am not sure yet what adjustment can be made here.
I learned two things: 1. Shuttle carriers can be adjusted on some vibrating shuttle machines, and 2. Look for screws to loosen things before bending metal.