Lionel 2343 Motor Question

this is a new one, these things are usually bullet-proof.  Run a resistance check on the coil  after making sure wire is not connected to frame when yo do so.... resistance should be nil;  check resistance between wire and frame, again with no obvious connections between wire and frame..  this should be very high resistance or no conductivity at all... if there is low resistance you have a shorted coil; when you reassemble the thing, run an extra ground from the motor frame to the chassis... make sure to polish and clean contact spots... no grease, corrosion or paint... just shiny metal. If there is  no short from the coil wire to the motor frame, the thing should still work. A dremel tool with wire brush will help clean contact areas.

One more thing,  when you reassemble the thing , one end of the coil does go to ground, typically either soldered to motor frame or to a ground terminal screwed done under one of the the motor screws. Make sure all connections are super clean and shiny, the one in the picture has a lot of stuff that needs cleaned if you want good electrical contacts.

I have had a fair number of Lionel fields with melted coil forms on my bench. In most cases the coil was fine.
Your coil looks clean, and the insulation on what is visible looks healthy. As John recommended, check the coil with an ohmmeter. The resistance should be between 0.8 and 0.9 ohms.

One time I decided it would be a good idea to use a low oven to dry out a 736 field that I had just carefully washed. Didn't turn out to be such a good idea. The coil form melted.
Fortunately the coil still worked fine, the operation of the engine was unaffected.

I wonder if that is what happened to your field. Or maybe a chemical reaction from some cleaner.
That does not really look like heat damage from a hot coil to me.

In my experience, when a coil gets hot enough to melt the coil form, the insulation on the windings is usually discolored or burnt.

Thank you for the advice and tips. I'll get to work. Jim