Yo SRS,

Change the oil. If its a walk behind, just get out a pan, take off the cap at the lower front part of the engine that says "Oil" and turn the mower on its side. It will take about a minute fir the old oil to drain out. Then right the mower and use a funnel to put new oil in the same hole. If there isn't a dip stick then fill until its just below the loest threads in the casting.

Now, take thre air filter cover off and clean the filter. You can clean it with water but be sure it dries before putting it back.

Lastly, if after you've done all those things, sharpened the blade and it won't start, you may have to turn the mower on its side again and drain the old gas into the pan with the oil in it and fill the tank with fresh gas....

If that don't work then your ignitor is bad and you'll have to PM fir directions on replacing it...

Bobert