A SMALL shot of ether (starting fluid) in the carb will tell you if it's an ignition problem or not. If it fires and dies with the ether, then it's a problem with the fuel system, and not the ignition. If the engine has been sitting unused with fuel in it for and extended period of time, the problem will most likely be in the carb as the crap fuel that we are forced to buy these days with alcohol in it deteriorates quickly and also has a tendency to absorb moisture, which then causes a buildup of deposits in the carb. Once you get it cleaned up and running you need to use a fuel additive if you're going to let it set unused awhile between uses, or run it until it's out of gas. I use Seafoam in all my equipment to keep things clean in the fuel systems.