Did you remove the spark plug(s) and spin the engine to expel residual gas from the cylinder(s)?
If not, that needs to be done. Wrap the spark plug boot in a paper towel soaked in water and lay it somewhere away from the spark plug hole while you give the engine a quick spin with the starter. The wet paper towel wrap is to stifle any chance a stray spark could ignite the gasoline
Do not place yourself in front of a spark plug hole, if gas in in the cylinder, it might be thrown on you.
One valve is usually sufficient to stop fuel drowning, if you remember to shut it off.
3 valves ain't enough if you don't use them :^)

This post was edited by mownie on Tue, Jun 17, 14 at 0:21