2 Answers

If it has sat awhile the gas may have gone bad . Also the rings will stick causeing some low compression . Pull the plug and spray some lube into the spark plug hole . Find the hose connection from tank to carb and remove and drain the fuel . Get some fresh fuel and replace hose re fill tank . Clean plug gap and replace  clean filter and wash  and dry . Use alittle starting fluid on filter. Crank it over and see . Rember that a engine  is nothing but suck squeeze bang  blow. Every thing has to work if not the problem is one of those . Good Luck                 Bill

Adding to what bluesman said, if you are stuck with the gas that uses the additive for emission control, that additive is known to damage the carburetors on small engines. I've had to replace 2 carburetors on my snow blower due to the additive in gas.