Bacon slicer advice needed

[Tony Press]

Highly likely the motor has been tampered with in 90 years-  it looks very new - I expect you have cleaned it within an inch of its life but possibly when last overhauled some time back  it was incorrectly assembled and when it didn't work properly  it was put to one side.

The commutator cover is not correct, it should have a 'clip on' cover with the body clips held under the terminal from memory. as shown in R's pictures

I suspect you will have to strip and check  the internal connections.