Hello, I recently bought a Bachmann spectrum k4 and upon testing it the train does move but when it's in motion it seems to be kicking up and down in motion with the driving rod. Any idea what this might be? I have no experience with steamers as this is my first, any help would be greatly appreciated!
Some of the older K-4's had drivers with what I call a plastic 'hubcap'. The plastic expands over time and bulges out; rubbing on the side rods.
Pop the hubcaps out of the wheel and cut them off/out with a X-acto knife. You can then paint the metal drivers black or leave them shiny. They look kind of neat that way.
Before;
(https://i.imgur.com/FUeMiuL.jpg)
After;
(https://i.imgur.com/z6mzUCb.jpg)
Check to make sure that the main rods and the cross heads aren't hitting each other. Sometimes the crosshead guides can get bent inward a little bit, causing the driver screw to snag on it.