[steve s]

If it ran fine the last time, and gas if dripping, the simplest possibility is that you've flooded the engine. The fix is to hold the gas pedal tight to the floor (or do this with the hand throttle ALL the way down) and crank the motor longer than you'd think--don't be pulling on the choke rod during this process! If it's flooded, this will clear out the fumes until enough air gets in to support combustion, at which point it will start to sputter, at which time you might have to choke it a bit to keep it going, BUT NOT TOO MUCH.

Make sure that no one has spun the gas adjustment valve too far open--turn the choke rod clockwise until it stops, then open it back up (counter clockwise) about 3/4 turn for cold start.

Once it starts, be sure to run it long enough to get the motor good and warm to drive off the gasoline that has seeped by the rings into the oil--a thermostat helps here, but them's fighting words for some folks.

Steve