Chainsaw Repair

Let's see.
You can pull the muffler and check the piston and cylinder.
Pull the plug and check it.
While you have the muffler off check the spark arrestor and make sure it is clean.
Check the fuel lines and fuel filter.
Check the air filter.
You can also try adjusting the carb.  Richen it up a bit and see if it makes a difference.
It could be the carb is bad.
You could have an air leak and so check the crank seals and intake boot.
Check tank vent for fuel.   Loosen the cap and try starting it.

With the H and L screws lightly seated( all the way in). one full turn out. Counter clockwise is stock setting. Should get you close