Put a small amount (tablespoon or so) of gas down the Spark plug hole, reinstall the plug and wire, if it fires then dies, fuel system problem, sometimes fuel lines come apart on the inside and clog things up.
Then spray some gas into the carb via the air intake, if it sputters or backfires, you may have a valve problem.
If it doesn't fire off, there should be a black kill wire going to the coil. un plug it, then try to start it, if starts. The wire is shorting and grounding the coil.