Mower starts up great and then dies

If it's a briggs engine, sounds like you have water / debris in your carb fuel bowl. Using spray carb cleaner will only work if you remove the bowl and clean the carb jets. Also, you could have water in the gas tank as well. First, remove your air filter, then remove the 3 screws that attach your filter bracket to your carburator and mower. Take off your fuel line at the carb and drain all your gas into a clear jar. If it looks very yellow, cloudy, or see water in the bottom of the jug, change your gas. Using a half inch socket wrench, after gas line is disconnected, remove the fuel bowl and clean with carb cleaner. Also, examine the bolt you just removed. There are 2 jets in the side and one at the end. Using the carb cleaner, make sure they are clean as well. Use the carb cleaner extension tube to spray up inside the bottom center of the carb, where the bolt threads, to clean that area as well. After all this make sure ur float assembly is intact and reassemblt the bowl to the carb and reattach the the fuel line. finish bt reattaching the air filter support bracket makinf sure the gasket between the carb and the bracket isn't damaged.

Your carb is either out of adjustment or it needs to be cleaned. The points or air holes are clogged. Spray some carb cleaner into the carb and let it sit it should solve your problem without having to take it apart

This is likely to be a fuel starvation problem.
Fuel is fed from a reservoir called the float bowl. This works pretty much like a toilet cistern with a float to cut off flow once it fills. Once the bowl empties and doesn't refill due to a blockage, the engine will cut out.
Clamp off the fuel line or turn off the fuel tap. Remove the bowl, and check fuel flows freely. If it doesn't, there is a blockage in the fuel line which you need to trace.


Another scenario is that the main fuel jet is blocked or semi-blocked. This can cause the engine to run ok when idling (since the idle jet is ok and not much fuel is required), but cut out as you throttle up. This is because more air is sucked in, but not enough fuel is drawn from the main jet due to the blockage. So the mixture is too weak and the engine stalls. The jet can be cleaned with compressed air or ideally a carburetor cleaning aerosol.

Smaller engines such as Briggs & Stratton 3.5 HP types have a diaphragm type carburetor. The tank is mounted below the carbuetor and a flexible section of the diaphragm is pulsed by suction from the air intake manifold. This sucks up fuel from the tank. Check valves prevent fuel travelling backwards. These are just flaps of plastic forming part of the diaphragm. Over winter, the check valves can get gummed to the carburetor body, preventing proper operation.

See my comprehensive guide for getting stubborn lawn mower or other small engines to start. This also covers issues with the ignition system:

http://hubpages.com/hub/Why-Wont-That-Lawnmower-Start

It is best to rebuild carb save money in the long term thats what us red neck do so should you