Answer to: Mower turns over, but will not startShort answer to my fix. To much gas in the fuel tank, gas cap vent clogged. I had the same problem, motor would crank but would not start. Before having the problem I installed: a new spark plug; new air filter; new gas filter and changed the oil. I was low on gas so I poured what gas i had left from previous week in tank. Not much, may a 1/4 gallon. Mower started like a champ. 2 weeks later I filled the tank and mower would crank but would not start. I assumed I fouled something up with the new parts. After hours of reading and researching. Trying this and that I asked a neighbor if he new of a good small engine mechanic. Neighbor ask if he could take a look. He removed gas cap and the engine started with no problem.