Stihl MS440 Magnum won't stay running

[Skillet]

So the fuel tank vent was it.  Fired it up last night, instantly idled down to correct speed and had instantaneous throttle response.

Thanks again all -

[Woodchuck]

good news man 

[BigGoonTuna]

pull your carb off and put a dab of grease on the impulse line.  give the rope a couple yanks - if it spits it out, you're good, but if nothing happens, it's probably got a crack in it or pulled off the nipple on the crankcase(fairly common).

[dbor]

Feul filter in the tank? Diafram, or maybe the sparke arester in the muffler.... it is a screen in the front of the muffler?? Just take it out and clean it.... don't use fuel... Good luck