Small Engines (Lawn Mowers, etc.): B & S V-twin 20hp, john deere l111, valve job

Question
I have a john deere l111 lawn tractor.  Whenever it is used for a couple of hours for mowing, tilling or snow blowing it likes to spit and sputter and loose power and finally quit.  It you choke it it will re-start, but you can't take the choke off.  I have replaced the fuel pump, coils, numerous spark plugs,and most recently did a valve job.  The valves have also been rechecked for proper setting and they are ok.The fuel filter get changed twice a year and the problem doesn't depend upon the outside temperature If you leave it sit for 15-30 minutes it re-starts and runs like a charm.  Is it a carb problem or something else?  I have run out of ideas and don't really want to spend any more money on this problem.  

p.s. the unit currently has 140 hours on it.

Thanks
Bob

Answer
Hello Bob:

You can View a Breakdown/IPL of the Engine and Mower at this Site Addy, http://jdpc.deere.com/jdpc/servlet/com.deere.u90490.partscatalog.view.servlets.H... and Enter the Model Numbers L111 and Click Find. Then Select your Model from the Search Results Area. Then Select the Sectional File. Then Select the Section of the Mower you Wish to View Online. 1- Check the Carburetor Solenoid and Make Sure it is Not Heating Up and Shutting Off the Gas Flow to the Carburetor Jet. The Following is a Basic Instruction File I made for Checking the Carburetor Solenoid. Any Input is Appreciated. **Check for Current/Voltage (10.5 VDC Minimum) to the Carburetor Shut Off Solenoid. If the Carburetor Shut Off Solenoid has Current, then On Some Solenoids you can Remove the Needle and Replace the Solenoid to Test them. ****PLEASE DO NOT OPERATE THE MOWER WITH THE SOLENOID BYPASSED IN THIS MANNER. THIS IS "ONLY" FOR TESTING.**** For Others, Remove the Carburetor Solenoid and Go to the Hardware Store. Purchase a Bolt of the Same Diameter and Threads. It Needs to be 1/2" to 3/4" Long for the Horizontal Mount Solenoids and 1/4" Long for the Vertical Mount Solenoids. Put this Bolt in Place of the Solenoid. If this Corrects the Engine Problem, then Replace the Solenoid. ***NOTE: THIS IS FOR CHECKING THE SOLENOID ONLY I NEVER SUGGEST YOU OPERATE THE ENGINE WITH THE SOLENOID OUT OF THE CARBURETOR EXCEPT FOR TESTING PURPOSES*** Sometimes the Plunger is Moving, Just Not Far Enough to Allow the Gas to Enter the Jet.**  2- What is the Engines Compression when the Engine Quits? 3- Have you Cleaned the Tank? 4- Have you Checked the Gas Tank Cap and made Sure it is Venting the Tank Properly? 5- Have you Checked the Pickup Tube in the Gas Tank? Some JD Mowers have a Problem with the Pick up Tubes and they have to be Replaced when this Problem Starts Occurring. 6- Have the Spring Style Hose Clamps been Replaced with Screw Style Hose Clamps? If the Spring Style Hose Clamps Get Old, they Tend to Weaken and as the Engine Heats Up the Hose Clamps will Not Seal Properly and you will Lose Fuel Pressure to the Carburetor. 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. Have a Happy Holiday Season and May the All Mighty Bless You and Yours. Be Safe and Happy. 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. Comments and Ratings are Greatly Appreciated. Thanks.

Respectfully

John