Today, I was gifted (cursed) with a serger that had been sitting in a storage shed for an indeterminate period of time. The above photo does not accurately represent the amount of dirt and insect droppings covering the outside of the machine but the photo below gives you an idea what I saw when I looked at it closely.
The rust was most severe on the exposed components, but the loopers were also rusty and thread needs to slide smoothly over the surfaces of the loopers. The machine was also frozen solid and the wheel would not turn at all. The first thing I did was to give the mechanicals a good soaking of Liquid Wrench. I kept trying to turn the wheel until it finally broke loose the tiniest bit. From there, I kept turning the wheel until I finally got one complete revolution, then used the motor to finish the job of loosening everything up.
The thing is a bear to thread and the lower looper thread broke several times but each time it broke, I would polish the looper and try again. Finally, I got a nice stitch with all four threads.
And here it is now. I still have some cosmetic cleaning to do in the nooks and crannies and testing some of the functions, like differential feed, but I'm pleased with the results so far.
As you can see, I installed threads the same color as the tension wheels so I would know instantly which thread needed tension adjustment.
I would not have taken in a machine in this condition for someone else because I was quite sure it would never sew again. I only did it because there was no pressure to get it done and no penalty if I didn't.