Small Engines (Lawn Mowers, etc.): Problem with a Brigs and Stretton engine, rotary hand, brigs

Question
Hi, I have a 4 year old Mountfield rotary hand-propelled mower powered by a Briggs and Stretton HP470 engine. The model number on the engine is 10D902, the type is 0141 81. I cannot get it to start, it was fine before i gave it a little service, so far i have emptied the old fuel and oil and replaced with new, removed the air filter, cleaned and soaked it in engine oil then wrapped it in a cloth and squeezed until no more oil came out, cleaned the spark plug with a wire brush, put it all back together again. It now will not start. When i pull on the cord it recoils back so fiercly it felt like i'd broken my hand. With the spark plug out, when i pull on the cord it feels smooth, with the spark plug in it doesn't. I left the spark plug out pulled on the cord a few times and i've left the spark plug out for over a hour thinking i'd flooded the engine, but still no difference.
Any help appreciated


Answer
Did you tilt the mower on it's side to perform maintenance?  If so, oil is in the cylinder which casues hydrolic lock causing the rope to nearly break your hand.

Remove the spark plug.  Pull the string really fast and see if oil squirts out the spark plug hole.

Let me know what happens.
Eric