You say it has has good fuel, good spark, compression if that is the case then it might be getting spark at the wrong time. Often fly wheel has a keyway that holds flywheel in set position, key may have broken hence timing out.
If spark plug dry after many attempts to start then no fuel getting to combustion chamber. Carb may need setting up.
Why did you change carb, if it was running before with old carb go back to the carb that worked
Maurice
January 2011