How long does it take to smoke a chicken?

While cooking low and slow has its advantages, 6 hours is a bit too long. You should be able to complete a 6 pound chicken in 1 1/2 - 2 hours @ 275°F [135°C].

Some things to remember that might help you out:

1. You are going for an internal temp of 160°F [70°C] in the breast meat and 170°F [75°C] at the thigh.
2. Every time you open the smoker you are allowing an ENORMOUS amount of heat to escape, this prolongs the cooking time. (If I were to bet, it would be that you are checking it too often)
3. Almost all the flavor your going to achieve from smoking is reached in the first 30 minutes. You may want to smoke it for 30minute - 1 hour and then transfer it to a 275°F oven if you are having issues maintaining the heat in your smoker.

From experience, I know that the longer you smoke anything, the better smoke flavour you will get.

Personally, I inject my meat first. The next thing is to maintain a temperature between 200°F & 250°F. I always check my wood and baste every half hour. I add coals every hour as needed.

With poultry, I remove it from the smoker while it is still a little undercooked and finish it in a covered roasting pan (with the rest of the marinade I used to baste) in the oven for about 45 minutes. This will keep your chicken or turkey from drying out.

I would smoke a 5 lb. chicken for 3 or 4 hours (130°F), then finish in the at 400°F oven until it reaches 170°F (approximately 45 minutes). It should turn out moist and full of flavour.

I smoked a 6lb chicken the other day... At 250° for 5.5 hours, after the first hour I was spraying it with Chicken broth. It was juicy and tender...smoke flavored all through.

I smoke a 6 lb chicken for 2 hours at 275 degrees but I also brine the bird for 3-4 hours before smoking. The brining keeps the chicken nice and moist. I use two trays of dry wood chips during the smoking period. Cherry wood is my preferred wood choice. I use the master built electric smoker.