Milly La Nordica cookstove primary air

[Morso1bo]

Hi, I am in my second season of using this cookstove and still have a few questions after re-reading the manual. I have been starting the stove with both secondary and primary air controls wide open, than comp closing the primary after 20 minutes. I than operate stove with secondary control wide open. The flu temperature drops to below 300F when the oven function is engaged, leading to some creosote build up. The owners manual states that the primary should be opened a little to ensure combustion, and at other times it says it should be closed when stove is fully burning. Thanks for any advice!