http://forums2.gardenweb.com/forums/load/lmower/msg061726346162.html

See this link. It's a place to start.

For your engine to start--you must have compression, fuel, and spark! If you know what those terms mean-then check to see if they are present. If any one, or more are not there, then some more checking is a must do.
First: Check the fuel tank, and the cap. Make sure there is no dirt, or old gasoline in it, including scaly rust, etc.
Second: Check air filter, look for caked on dirt on the sponge type filter.
Check gas cap breather hole. Little bugs like to make their nests in that hole, which plugs it up and fuel won't flow out of tank!
Third: Check oil level, either by the dip-stick, or remove filler plug, look to see if oil is level with top of hole. Note: If you get engine to run well, then change the oil: SAE 30 will do.
Note: If you do get the engine to run,, it might be wise to change the oil.
A new spark plug is a must. Set gap to .030
Also, if it runs well, then install a fuel shut-off valve, for when it is sitting idle. The carburetor should be given a thoro cleaning. Sometimes the carb. float will stick open, and fill the crankcase with raw gasoline, witch usually ruins the engine when you try to start it. After some work, if the engine hasn't been ruined by running with low oil, or a flooded with gasoline condition, It may be ok to use. RJ