While the consequences of just hitting this thing with 5 amps of Dc (or for that matter, AC) are not truly catastrophic (motors are cheap) i would recommend disassembly, degreasing, re-lubrication, and hand- operation before going another futher.
Try the motor by hand as well, then lubricate it and run it without hookup for a minute or two.
Only then, clean the wheels and track test.
My hand-built and carefully lubricated models seem to freeze up in a decade.
