Does it have a fuel pump or is it gravity fed? If it's gravity, pull the line off the filter and see if fuel runs out. If it has a pump, you can do the same thing by turning on the key to see if it pumps. WARNING: if you turn on the key to try this, make sure the gas is flowing into a safe container and BE SURE TO HAVE A FIRE EXTINGUISHER IN YOUR HAND. A spark can make things lively real fast.
Oh, and whatever you do, don't pull the spark plug and then crank it. The piston will spray gas all over the engine and the spark will ignite it.