I have a 12.5 hp Briggs 289707 which had not run for a couple of years. After replacing the starter I put a small amount of gas in the tank and the engine started right up and ran at full engine speed for a few seconds and I then shut it off. I started it again and it ran for a 10 seconds or so and if I recall it stalled. My suspicion was that the gas ran out so I put in a quart or so this time. Now the engine barely idles (very slow and it seems it is missing more than firing). I am also getting what seems to me to be a lot of back pressure through the carb and I also get a bit of a backfire when it dies. Engine speed does not change if the throttle is wide open or when I close the throttle with my finger on the governor (just the sound changes a bit).

I pulled the carb off and cleaned it up as best I could and I also adjusted the intake valve lash (it was a bit tight so I filed it down). Valves were working fine and were moving freely.

Still no change; barely idles with throttle wide open.

I gave it a spray of starter fluid while it was running and nothing happened (actually it stalled out when I sprayed a big dose), no increase in engine speed.

Does the fact that the engine doesn't run any faster with the starter fluid rule out carburetor?

I am thinking ignition, either bad coil or timing is off (flywheel key).

Thing is it ran just fine for the first 20 seconds or so and I did not even try to go anywhere; could the flywheel have jumped???

My bet is coil, anybody seen this before?

Thanks.