This is why putting your thumb over the carby inlet helps work out if it is an airflow problem through a gasket failure, always try the simple things first
This why I use block offs and a pressure/vacuum tester. If tester indicates a pressurization and vacuum is just a negative pressure then I positive pressurize and use soapy water to find the leakage. This does however loosening the carburetor and muffler to insert the block offs and re-tightening them to seal. Some seals leak only if a vacuum is pull or if only positive pressure is applied.
But if you work on these enough you get a set initial test procedures that work for you. Things like will it fire fuel prime. It usually takes me about 15 minutes using none invasive tests to determine what is most likely wrong with a two cycle engine. It take more time of course as you got to get the test and hand tools out and back up. None invasion tests save a lot unnecessary tear downs.
