Small Engines (Lawn Mowers, etc.): John Deere LX279, fuel pressure, gas cap

Question
i have a john deere lx279 - had it for several years. i mow alot of grass and have run it very hard.  it has always been great especially for the hard load i put it under.  lately, after 20min or so of mowing - it cuts off.  i can keep it cranked if i push the choke up - but it will cut off if i don't choke it.  if i let it cool down it will run again for about 20 minutes and then the same thing.  i have read lots of posts about kinda the same thing - but not about the choke keeping it cranked.  do i just need to clean the carb. or what?  please give a detailed answer as i am not good at fixing this kinda thing.  thank you.

Answer
Hello Adam:

Usually when the Choke has to be Used to Run an Engine when the Engine is Hot; this is Due to the Rings Being Worn and are Unable to Expand as Much as the Cylinder has Expanded. This Causes a Loss of Compression (and Suction) and then the Engine Does Not Draw the Gas through the Carburetor Unless the Choke is Applied. However, it May Also be; 1- The Gas Cap is Not Venting the Tank Properly and Causing a Vacuum in the Tank. 2- The Fuel Pump May be Heating Up and Loosing Fuel Pressure to the Carburetor. Check the Fuel Pressure when you are having to Use the Choke to Run the Engine. 3- Check the Compression when the Engine is Cold and Again when the Engine Quits. What are the Compression Readings? If you Hit a Snag or this Does Not Correct the Problem,  I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Thanks.

Good Luck

Respectfully

John

PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 8pm EST (US). My New Day Starts then. Thanks.

Respectfully

John