It may not self excite from that shunt field but you could excite it from the battery via a series resistor if necessary.

You may have to dive inside and reverse the connections to the series field or possibly bypass it completely if you have enough shunt winding.

I suspect you can do it but without detailed knowledge of what the motor is wound as you are in the realms of experiment.

It will probably need to be driven fast.

I strongly suspect that the field connections that you have access to are a shunt winding and they may look to be lower current connections than the armature terminals.

If the field terminals are very heavy with very thick leads then it is probably a series winding. If it is series only you will have to do some serious tricks to use it.

An interesting demo in electrical engineering "big rotating machinery" lab is the one where they hook one motor-generator pair up as a series-connected generator and the dc side of another as a motor - with the field excited separately.  They make a circiut composed of the series combination of:
 - The armature of the motor
 - The armature of the generator
 - The field of the generator
 - A big resistor (think ten space heaters and switches to connect them in series-parallel connections to get the resistance they want).

The motor starts spinning up, then suddenly WHAM! it "slams on the breaks", the "oven" flashes bright orange, and the motor starts to spin up in the opposite direction.  This repeats every few seconds.

What happens is that initially the generator starts putting out voltage, which drives current, which increases field, which increases voltage, etc.  The voltage ramps up rapidly and starts spinning up the motor.

But eventually the motor starts developing a voltage across its rotor that opposes the current.  The current drops, which reduces the field excitation, which reduces the output voltage, and the whole positive feedback thing happens again, this time driving the field through zero into the reverse voltage in a fraction of a second.  The current is even larger (because the motor is also driving it).  So all the kinetic energy of the motor is dumped into the resistor and the motor starts spinning the opposite way - eventually spinning fast enough to do it all again the other way.