When I get the fire going good I close the bypass and the stove exhaust through the combustor. When I do this it chokes the fire down and there are no flames. My question is.... is this normal or is the combustor junk... I bought the stove second handed. I have around 5 feet of single wall pipe connected to 6 feet of double wall insulated class a pipe. When the stove is in baypass mode it runs good but when I close the paypass it seems to choke down the flames and heat output. Any idea...