(ET) Motor question

["Rod Hower" <Rod Hower ametek com>]

I have a 13" compound wound 72 volt forklift motor in the garage.
This motor can run (slowly) with a 12V automotive charger connected
directly to the series field (no voltage on the shunt field).
The no load current is about 4 times higher, but it still runs.

Since the ET has a compound motor, I figured I could do the same test.
I jacked up the back wheels and put the charger across the series field,
but the wheels didn't turn.  Has anyone ever tried a similar experiment?
A friend told me it had a weak series field, but I would think it is strong
enough
to turn the wheels when its jacked up.  The motor was definitely drawing
current, you could hear the transformer humming.