I have a three year old John Deere JS46 walk behind mower with a Briggs Engine. The mower has had very little use. Lately, it has gotten harder and harder to start. Fresh fuel, clean air filter, new spark plug... It takes several hard pulls on the cord, and it usually just makes a ffffft ffffft ffffft sound, and it sometimes backfires. After a few pulls, it'll hit a time or two, then finally catch, miss some, slowly build up to speed, and then finally start running fine. If I shut it off hot, it is just as hard to start as it was cold. I'm not sure if this is related, but when it is running, the engine will often surge and run fast briefly when under load.
This engine seems to have an easy start feature that floats the valves to reduce compression when the cord is pulled??? If so, it almost seems as if the valve isn't closing so the engine can start. Sometimes, it acts as if it is flooded. I just can't any obvious problem.
Does anyone have any ideas?