[drolston]

What has changed since the engine was last running okay? Any modifications, upgrades, or adjustments to the engine, ignition, fuel system?

If the spark is good any you put a few tablespoons of gas down the carb, it should fire and run for a few seconds, even is the carb is completely bad. Very strange.

Check the spark plugs. If they are wet, oily or sooty, replace them with new plugs, and then crank it with a little gas down the carb. Should fire.