This has happened to me where it turned out to be a sticking intake valve on a Briggs engine. Pull the plug(and ground the cable) and do a compression test. If you dont have a tester, afinger over the plug hole will give you an idea if the cylinder is building pressure. If it isn't, disconnect the battery negative lead, Then bend a wire to fish in through the plug hole, feel for the valves. Check operation of the valves with the wire while slowly turning the engine by hand. If a valve isn't moving, work a penetrating oil sprayer straw in to where it will spray the valve stem and give it a small shot. Pull the straw out and turn the engine to where the unstuck valve is open. Now try to push the stuck valve down with the wire. You may have to use a heavier wire for this. Once it is down, turn the engine by hand to see if it goes down on its own on the next revolutions. You may have to push it down and spray it several times until it frees up. To reduce the chance of this I use Marvel Mystery Oil in my gas and park engines on the compression stroke so the valves are closed. Good Luck
Edited by boyscout862, November 18, 2012 - 11:01 AM.