Burning Fir For Firewood

[Toepopper]

This year I decided to cut up and burn some Douglas Fir saw logs I took down 2 years ago. Couldn't sell them as fir prices are in the toilet due to no new construction. I had split up about 3 cords of fir and have been burning it along with madrone all winter. Last week the woodstove started blowing smoke everytime I opened the door to put more firewood in it. I climbed up on the roof and the chimney cap was coated in a black tar like substance that was dripping and oozing down the outside of the chimney. This tar is caused from burning fir and is created by the resin and sap inside the wood, which turns into tar when burned. I scraped off as much tar as possible from the chimney cap and surrounding area but how am I going to remove it from the inside of the chimney? What a mess. I've still got 3 fir trees about 130 feet long laying down on the ground but will cut them into dimensional lumber rather than use it for firewood next season to prevent this from happening again.