I tipped the mower the wrong way to clean it and oil leaked out of the carburetor. At first I couldn't start it at all. I cleaned up the oil from the intake holes and cleaned the air filter. I checked the spark (good and strong) and there was gas in the tank. Still not firing. By covering the air intake with my hand I was able to get the engine to start and keep running by 'dancing' my hand over the air intake - varying the air entry. As soon as I stop the engine stops. Now, with the air filter and cover back on it may start after being left for a while but stops immediately.
