Gentlemen... Newbie question After having used this saw for about 2 cords I managed to smoke the bar (plugged oil ports & didn't catch it in really dirty wood). I have been on the Oregon site and they recommend D72 bar & chain combo. The local Poulan (service?) center says D70. Who's right??? I want to get a bar & chain combo that will allow me to use the original chain as a second chain.