The old Kenmore 2142 is a large and heavy sewing machine, but threading it is very similar to threading any Kenmore machine. The Kenmore 2142 is the common name for the Kenmore 158 and 1750 series of sewing machines. The model number 2142 was for the motor used in several different Kenmore sewing machines at the time. You can thread nearly any machine with a Kenmore 2142 motor the same way.
Place a spool of thread on the thread holder at the top right of the machine. Top with a plastic spool cap, if available.
Rotate the handwheel toward you until the needle is raised to its highest position. This will make threading easier.
Pull three to four inches of thread from the spool and pull it through the silver rear thread guide at the top left of the machine. Pull the thread toward you and down toward the base.
Draw the thread down and around the tension disk or check spring (a round knob on the front of the machine).
Loop the thread back up to the take-up lever (the slotted metal bar that moves up and down with the needle).
Slide the thread back down the front of the machine and thread it through any remaining thread guides near the needle.
Thread the needle from front to back and pull an inch or two of thread to make sure it won't catch on any parts as you sew.