When I get a good wood fire going in the wood stove, then close the draft and set the flue damper,why then do?

the fire puff and roar as if it were about to blow? The puzzle is that I know when you open the draft and open the flue wide, the fire will pick up and roar as you expect it to do, why then does it roar ( just for a few seconds) when you close everything? It must have something to do with the heated ges given off? I should also mention that this is a hand made stove, converted from a thick walled old propane tank (cut and welded)