I have a Lawn Boy 1683 mower. Its performance has been superb since I purchased it in 2005. The last time I used it was about three weeks ago, when it worked fine. Now it won't start. It has fresh gasoline, a clean air filter, and the spark plug appears to be in good condition, but I cleaned it anyway.

I sprayed a shot of Chemtool cleaner into the air intake and the mower started up right away, so I assume the ignition system is working fine. The engine ran for maybe 10 to 15 seconds, and then it quit. A fuel problem?

So I drained the gas tank, removed the carburetor, and cleaned it with Chemtool. There was a tiny bit of gooey, yellowish gunk at the bottom of the float chamber, underneath the float, but otherwise everything looked fine.

I reassembled everything, and the problem was unchanged; the mower won't start. Another quick shot of Chemtool to the air intake and it started again, ran for 10 to 20 seconds (kind of pulsing...not at even speed), and then it quit.

I opened the drain plug at the bottom of the float chamber and gasoline streamed out, so the fuel is definitely getting into that part of the carburetor.

I would greatly appreciate any suggestions.

Thanks!