I havr a kenmore 50! I love it, its my first ever sewing machine. Ive never tried timing from the top part of the machine, ive worked from the bottom. This method seems easier she explains why the bottom thread isnt being picked up. Ive timed a different machine. My model 50 is a dream machine.
https://www.youtube.com/watch?v=LmEtmnkDIS8&feature=youtube_gdata_player