Small Engines (Lawn Mowers, etc.): mower shut off, crankcase pressure, oil seals

Question
i have a 20 hp gravely rider. i can start it then it will sputter then smoothe out then when i stat to mow it will run bout 5 min the cut off. then when i try to restart it will do nothing no noise nothing. then after 10 min  it will start then cut off again i going nuts do i have to slit my wrist?

Answer
Check the fuel system first.  It sounds like it may run-on only the fuel in the carburetor bowl and then quit until the bowl refills.

In most riders like yours there is a delay switch the delay switch is there so the electrical system will not cut out on bumpy ground.  You could have a delay switch that is bad some places will also call ita relay.

If it is electrical I don't think the trigger ring is breaking down but it would be nice to know if you have spark when you're trying to restart the engine.  If you turn the PTO on and off or move around in the seat or use the break or clutch will it start easier, or quicker?  My thought they are being that you have a bad ground or a loose wire someplace that is coming apart when you are operating the machine and then reconnects when you engage safety switches to restart the engine.

The most inexpensive way to do this would be to try cleaning the entire fuel system first clean the fuel cap vent, tank filter at the outlet and fuel lines.  I am confident this engine has fuel pump.  Most likely it is a pulse pump meaning that it has a diaphragm and receives pulses from the crankcase to operate.  Be sure the system is clean and operational.  Is there oil inside the air cleaner on the engine side of the element?  If there is you are blowing oil out of the breather and directly into the engine this is caused by positive crankcase pressure.  Positive crankcase pressure is caused by an air leak.  The most likely places are the oil fuel to O-ring, the dipstick O-rings, crankshaft oil seals, crankcase gasket or the breather.  Lastly start checking electrical cause.  Start with the ignition system are you losing spark once the engine begins running?  This could be a bad trigger ring if you have a Kohler engine or bad coils on a Briggs or Kawasaki.  I know this is a lot of information I hope I helped.

Good luck in your project.