Is there a spark at the plug.
Did the flywheel key shear and throw the timing off.
Try some fuel down the plug hole and see if there is
a kick of some sorts.
When did the saw last run, did it die and refuse to start,
has the saw lay up for a period with fuel in it, have you
tried replacing the fuel with new fuel.
Have you looked at the fuel filter to see if it is clogged,
how about the fuel lines, the vacuum line, is it on off
or cracked, same with fuel lines, are all the linkages on
the carb connected up.