Small Engines (Lawn Mowers, etc.): still chain saw, carburetor body, carb settings

Question
I thoroughly cleaned my stihl chain saw including the carburetor.  I adjusted the
carb settings as instructed.  The idles run smoothly.  When I attempt to cut and
the saw is under strain it dies out.  I am at the end of my expertise.  Any
suggestions?
Thanks, Jim

Answer
There are two circuits in the carburetor and idle circuit and a run circuit.  It sounds like to run circuit is still plugged or has a small piece of debris in it.  I would start with the fuel tank remove the fuel cap and clean the vent.  Next flush the fuel tank being sure to back flush where the fuel comes out.  Install a new fuel filter install new fuel and primer lines.  At this point I would try it and if it still is doing it remove the carburetor disassemble it and cleaned every fuel and air passage you can find with a wire from a wire tie blowout air and fuel passages with carburetor cleaner or compressed air.  On some carburetor's there is an internal screen that will need to be removed and cleaned or replaced.  If there is a Welch plug in the carburetor body remove it and clean the passage behind it.  Purchase a carburetor kit from your dealer and install it remount the carburetor using new mounting gaskets.  Make initial adjustments on adjustments screws start the engine and make your final adjustments.  I think that somewhere along this troubleshooting path you will find your issue.

The other thing you could do before starting this process would be to check your compression with the compression tester.  I think steel chainsaws run at about 90 PSI but check the website or your owners manual to be sure.  If this saw has many hours on a it may need rings crankshaft seals and cylinder gasket.  I hope this information helps good luck on your project.