Did you check the spark arrestor?

Also check the fuel line, it may be cracked.

Thanks for the replies.
buttlint,
The spark arrestor is clean.
canguy,
I have not checked the fuel line. Could that be checked by unhooking it from the carb & blocking one end & blowing air into it?
As I stated in my original post, I need to get a new valve, (part # 1110 353 1600), which I hope to have tonight. I'm hoping that will fix it but if it doesn't, I'm looking for other causes in advance.

How about the impulse line from the crankcase too the carb manifold? They have been known too slip off of their connections and cause similar symptoms.

buttlint,
I put a new fuel line and tank vent in last night and it is still the same. I saw the impulse line mentioned in the sevice manual and was wondering about that. The manual is vague about what the line does. I did notice that if I loosened the gas cap it would run maybe a little bit better.

flh,
The impulse line operates the fuel pump in the carb. As the engine turns the crankcase pressure fluctuates opening and closing the fuel pump flaps (and other things) with vacuum or pressure pulses.

How does it respond when you open and close the low speed adjuster? If no responce carb still has a little dirt in it. If it still has the epa tabs on the adjusters you might have to take them off to adjust it right. Steve

Thanks everyone. buttlint was right. The impulse line had come unhooked. I hooked it back up and BINGO! It runs like a top.
Thanks again. I was just about ready to take it to a shop.
Who knows what that would have cost.

I have a Stihl 020T with a broken chain-side cover (sprocket cover). Any idea where to find a used one?

ebay would be about your best bet, even then I don't think you will have much luck. Those climbing saws end up with alot of broken and smashed parts :). I know my 020T has, lol.

I suggest getting rid of it, I have a 020t also and I find they are rather hard to keep running good. I prefer Husqvarna but if you don't have the money or don't need it for more then the odd job as a homeowner... arbouist chainsaws arn't worth it. If you wish to fix this problem you'll need to let it sit for a few hours because you might of flodded the engine, arbourist chainsaws are very delicate when starting up. After letting the gas flow go even, full choke it till it "cracks" or "pops"(sound)then half choke it and it should start right up. If this doesn't work only thing wrong with it I can think of is the gas hose lines. If they suck more air then gas it will blow apart your piston. Also make sure the gas/oil ratio is right and such. If this doesn't work let me know how this reacts and I'll help more.