Non working 1982 GE Gas Fired Forced Air Furnace

The GE furnace is a model BLU055E936.

Problem: The blower motor hums and if I don't turn it off immediately,
it would burn up. I know this because this is the 3rd motor this
winter. The motor will get up to speed if you secure the service door
switch and wait for that moment when it just starts to hum and then
give it a push start with your hand. The blower motor won't come on
even when the fan is selected on the thermostat.

Attempted Fixes:
Everything electrical and mechanical has been replaced, which
includes:
Motor, Capacitor, Relay, Transformer, Limit Switch, Thermal Coupler,
Gas Valve, Fusible Link, Thermostat and all low voltage and hi voltage
wiring. All of the parts were ordered using the information on the
furnace. The wiring was rewired using a schematic for this unit. The
breakers and wiring where the power enters the house has be cleaned up
and new breakers installed.
We have even had an HVAC Technician come over and he was unable to
figure it out.

Is there anyone out there that can shed some light on a possible fix?

Thank you very much in advance.