General Question on Coal Feeder

That’s interesting that the design is for the combustion blower to shut off. Well I learned something new today! I would think that on and off cuts down on efficiency, but may not be worth your effort depending on how much you want to get into this project. Do a under grate cleaning and clean the grate holes first. Oil the motor too. See if it makes a difference. Might eliminate those unburnt pieces. Sounds like you are already getting a lot out of one bag.