Because there is water in the fuel line. Drain the gas tank, fuel line and the carcuretor bowl. Then put new gas in it.
There could be many reasons why your Sears riding lawn mower won' shut off. The key could be jammed for example.
When you turn it off the igniton (spark) to the plug stops as the engine rolls to a stop unburnt fuel collects in the muffler and is ignited by glowing bits of deposits.
Let go of the "deadman" handle.
It can fall of your mower if you haven't screwed it on tight enough for it to stay
The kill switch wire is broken or has come loose. If it is a push mower, look at the end of the throttle cable where it touches ground when the lever is in the OFF position. If it is a riding lawn mower, follow the wires from the ignition switch, you will find a disconnection someplace near ground (by the throttle cable bracket on my rider).
Most new mowers have a cut off switch inside the oil filler tube that shuts it off when the oil gets to low.Seeing it is a new mower the oil will burn a little causing the shut off to activate,put some more oil in it and it should be ok.
with a kohler regulator tester
how does the power take off system work on 1200 Massey Ferguson lawn mower
It is possible but not very common. Usually a bad carb will cause a non-start issue or it will shut off within minute or two if it has a stuck float valve causing it not to get gas.
If the fuel filter isn't clogged, the carburetor main needle valve may need to be adjusted.
floor or bumper jack
because it is out of petrol and broken