I did a complete teardown on an F-3 for headlight improvement. Does anyone know what position the "key tab" on the worm gear bushing goes between the chassis halves? I took a guess and placed it straight down. The engine runs, but it's a bit wobbly and hesitant at times. Looks like I may have to tear it down again and do some tinkering with the internals.
In case you're curious, I cut the headlight circuit off an old N-scale decoder and placed it at the rear of the chassis. Ran wires forward to a tiny square LED and installed it up front, right behind the shortened headlight tube. Works great - really bright now.