I accidentally put 2 stroke gas in my lawnmower. My neighbor cleaned it out but it still will not start. Any suggestions? Thanks.

Uh oh... I would take it to a professional.

No need for a pro.. 2 cycle oil/gas mix isn't harmful to the engine at all... (its how I get rid of my old mix, so I know)... Change the spark plug out for a new one (preferably a autolite or ngk, dump the champion if it has one) you might have fouled the plug.