I was mowing a lawn and the neibor ask me to fix the lawn mower I said I dont normaly fix lawn mowers (I was planing to) but I would do it. heres my problem I did an oil change and it had old gas in it so I drained that out and put new gas in. it would not start I checked the spark plug and airfilter they both apeared to be fine, what else should I Do/Check?
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Did you see if the spark plug was sparking? If you unscrew the plug from the engine and keep it plugged into the wire, when you pull the start cord, if the plug is touching the engine block, you should see it spark and if you don't that would lead to another problem.