I wonder why that seems to be a common feature among Baker engines. All the Baker engines I've been near or seen videos of are rolling coal pretty hard. Case Frick and Port Huron engines will usually clean up when pulling a load because they finally get enough draft when working.

Miniature engines fire very difficultly. It's not as easy as larger engines. They always smoke more since they aren't designed as well as their larger counterparts. Another thing. If you notice, as soon as the load is hit the smoke cleans up a bit. Which means the fire is correct. If it didn't smoke under no load, the fire would be way to light causing damage to the tubes, and loss of pressure. The guy on the Baker is firing a little heavy, but not by very much. The fact of the matter is, those miniatures don't draft for nothing so he's probably just barely keeping steam up. A little blower would probably be all he needs.

Besides that, they are running a sawmill so they shouldn't be firing with coal anyway! May as well burn the slabs they are making..