spray a little Starter Fluid into the carb intake or spark plug hole.. try to start. If it fires up you've got a fuel delivery problem. If so, check/clean the carb and entire fuel pathway.
if it doesn't fire up either you've either got no spark or not enough compression (need about 80psi to start.. about 120psi to have a healthy engine) Check wiring and switches for no-spark .. use a new plug..
It's rare to have no compresion but since this engine was run without oil for a while, it could be. Use a compression tester. If rings are ok, check for a warped head or some other major leak above the rings.