@Richie C. The pic you posted is the '48-'49 model, there are differences. Did you look at the Lionel Service Manual hosted in Olsen's Toy Train library? http://pictures.olsenstoy.com/2026-51.htm You might be able to find photos of one disassembled on a popular auction site, or elsewhere on the internet. (You can also search for the 2018 because mechanically it's the same.)
From my own imperfect memory, the smoke lever is wedged between the steam chest and the chassis. There were no "bearings" for it to ride in, as such. As it says in the service notes, it would occasionally bind up in operation. Hope this helps!
