Chainsaw Repair

 Hi, this is my 1st post. I have an old 041 Farm Boss (non AV) with a Tillotson carb. In the 70s my boss gave it to me when I left his tree company and headed to university. In the past twenty years I've run it about once a year, usually for a good workout of a few hours of falling or bucking or trimming -- and its always run like a trooper, only occasional trouble with a plugged oiler.
However, today I had a tough time starting it, and when it got going it would only run with the choke mostly out.  It ran pathetically for about an hour or so, (trying to buck up an old cedar stump which my wife rightfully thinks is an eyesore in the corner of our yard... she arrives home tomorrow from an 8 day trip, and I wanted to impress her with my diligence...sigh) Even when it was all warmed up from cutting in it's feeble condition, I couldn't move the choke in - it had to be almost all the way out. When I pushed the choke in, the engine would rev high momentarily, and then die -- and if I quickly moved the choke out again, the engine would catch and keep running.
But it has no power, none of that old dogged torque and strength that would chew thru a log... I have to nurse it along at low rpm and it easily bogs down so I can't even use the full edge of my 18" bar. Pitiful...pathetic... embarrassing for such a noble saw... it took ages to make a few cuts...
   I'm on a tight budget so don't want to take it to the shop. I'm a backyard DIY guy and pulled lots of engines and carbs apart, but never my 041.
I looked on the web but can't see any video/forum that actually talks about doing carb adjustments, or even a diagram  of this carb and what/where adjustable screws it has, and how many turns out after you've screwed them in all the way.

I've appreciated the detailed, knowledgeable responses I've seen in this forum to other questions -- I'm looking forward to hearing your wisdom.  Thanks in advance for taking time to help me.

Start with the cheaper things first like a fuel filter and fuel line.

I've back flushed bad fuel filters and made them work a while longer.

You can inspect the fuel line for cracks

Check the the carb is tight etc.