How come mostly every single stihl saw I see has a ton of black (looks burnt) where the bar connects to the sprocket, behind the cover? My old man bought a new 250 maybe 8 years ago, and I was flush cutting a stump that was pretty big, and it was quite black when I was done. Looks like the exhaust exits in the direction, and maybe since it was close to the ground the heat had no where to go? I brought It back the next day, and the guy said the chain was dull, and thats what caused it. I've been cutting for 20 yrs and change out chains immediatly when they get dull. (random saw to show what i'm talking about) .