You mean by adjusting the draft right?

We purchased a "lightly used" St Croix SCF 050 corn furnace from a dealer and have had unending problems. After two visits from the repairman we still have the problem of pellets pouring through so quickly that the pot overflows, the pellets that have overflowed continue burning and the house gets flooded with smoke. The repairman has reset it twice now after thoroughly cleaning the furnace and it runs okay for a few hours then begins overflowing again. Last time he was here he removed the motor and found remnants of some kind of creature (possibly a bat) clogging it up. He cleaned it out, reset the board and same problem. After calling to report the problem again they want us to buy a new motor (an additional $300 w/labor). That makes a grand total of almost $1000 just to try to get it running right. Any suggestions?