check the guage of the lead truck - it may be off slightly, causing the wheels to bund in the track and jump off. Also, you will want to make sure that the lead truck pivots freely, and that it doesn't have too much vertical play. One last thing to do may be to check if it is missing any springs that are/were used to keep that truck against the railhead.
Builder of Bowser steam! Railimages Site
Lionel collector, stuck in an N scaler's modelling space.
NO, don't take it over there. They have little to no experience with Lionels. This type of thing would be better posted on the Classic Toy Train forum.
Have you checked it out statically - jacking it up with Lego bricks or something so it will still run? I did this with mine because it made funny noises and lurched. Turned out that there was too much play on the rods and the traction tyre stuck out too much. Fixed that by shaving it down and thereafter it ran much better and derailed less.
However I think its the pilot thats the problem, mine can be turned around so its sort of running backwards and tilted up, well it only happened once after a crash. Some folks swear by wrapping solder around an axle to weight it down more and some have claimed that the pivot is in the wrong place and needs repositioning.
Just some ideas
my trucks where stuck or kept derailing.i took out the the spring and now the trucks arent stuck and dont derail anymore.