You're overthinking it. A gasoline engine only needs a few things to run. Fuel. Air. Spark. Compression. You need to check all of those first. Fuel won't do any good sitting in the float bowl. If you can't see gas vapor in the intake then you've got clogged jets. Next is the spark. Pull one of the plugs and hold it against the head or rocker box, then crank the motor. No spark, then it's the plug, wire, coil, or trigger mechanism. Do the simple stuff first.