Thank you richg and Doneldon,

The wheels that tend to not stay on the track are the front four wheels on the engine that move together. The whole wheel mount is spring loaded to the engine. Adding weight to the tender (coal car) will likely keep the contact good to the track. But how do I add weight to that car? Disassemble it?

I will clean the track and the wheels and see if I get some improvement.

I have this Buchmann engine, the 119. the front set of 4 wheels do not stay on the track very well. Also the rear coal car that is the power connection to the track does not seem to have enough weight for the engine looses power.

Any suggestions on how I can fix these?

Thank you.