I tipped my lawnmower over completely. I am trying to replace blade and was successful. My lawnmower starts but doesnot stay running. It spits and sputters. My wife took out the spark plug and cleaned it and sanded the end of the plug. What is my problem and can you help me?

You likely have oil in the combustion chamber, never tip over an engine. Also never sand a spark plug. Remove the plug, spray some carb cleaner in the hole and let it sit while you go buy a new plug. If you don't have a feeler gauge ask the store to gap the plug for you.

In general, lawn mowers and the like, are fairly primitive beasts in the engine world. Only two things can really go wrong, Electrics or fuel.

Pretty sure it's not an electrical problem unless it's a trapped or crushed wire and when it heats up it becomes pliable enough to short to the chassis.

I am pretty sure that it's to do with the fuel line. If you turned the mower upside down, I reckon you have an air lock, which explains why it starts and then stops.

How long doe sthe mower stay running?

Hi,
It is certainly an oil contaminated(and/or gas) air filter. Try a 491588 air filter.
Peace,
Clarke