Operating by hand is first in assessing new used machines. If there is no needle to bobbin problems I proceed. if there is a timing problem, it is contended with. If it is fixable, I fix it, if not it's set aside as a parts machine. The top is removed and all metal to metal parts oiled. I am using up a quantity of Zoom Spout oil and will switch to TriFlo eventually (by all recommendations from posters). Then the metal to metal parts of the nose are oiled. I proceed to the under carriage and oil and verify intact properly adjusted rods, feed dogs, etc. If there is a lint and/or thread buildup, I take it outside and air pressure the begeesees out of it. This also will remove most excess oil. Only then do I attempt sewing. Upper thread tension is left alone for the time being. If it sews within normal parameters I tinker with the tensions with opposite colored threads in upper and lower tensions. The different colored threads show up improper adjustments more readily. If the tensions need work, I start with the upper. If in range I leave the bobbin case alone. To get a tight stitch I will adjust the bobbin case tension along with upper tension, but rarely have to do this for normal thread usage.
Once the machine is sewing properly, I clean the outer case with flannel and oil. For sticky stuff I use alcohol on non-Japaned machines. The Japaned machines I clean only with oil. Silvered decals ruin the machine for me. No volatile solvent is used on the Japaned machines.
My original intentions were to recondition and resell machines. So far I've sold one, my mothers Riccar ZZ. I offered a recondition Elna Supermatic in pristine condition on eBay for what I had in it and never got a bid. So, this has become a collecting hobby for me and history predicts I will eventually move on to another hobby and have a bunch of nice machines adorning shelves. Anyone want to see my gun collection, camera collection, or watch collection? My dear wife made me dispose of my car collection - took up too much room. She may have input into my sewing machine collection soon😀.
