Small Engines (Lawn Mowers, etc.): Riding mower will not start, sears craftsman lawn tractor, craftsman lawn tractor

Question
QUESTION: Sears Craftsman Lawn Tractor 17hp Kohler
Model No. 917.272084
SN  032802C001767
Hi, The engine in my almost 6 year old mower will not start. It will turn over, but not catch. I've changed the gas, fuel filter, oil, air filter and spark plug. I pulled the carb and cleaned it with Gumout. There is spark, the soleniod on the carb moves when the ignition is turned to on, yet the motor won't catch. I think the final two bits of information are that for about the last year the engine sputters a lot of gas thru the muffler when starting but has always run fine. The final bit is that after the last time I used the mower I washed it. I probably only let it cool for 10 minutes or so, but 30 minutes after washing it I started it up and drove it for 5 more minutes. I appreciate you help with this,
Thanks, Ken



ANSWER: Hello Ken:

Will the Engine Start and Quit if you Use Starter Fluid or Pour a Small Amount (1oz) of Gas Into the Carburetor Throat. If Yes, then the carburetor Needs to be Cleaned.  Remove, Disassemble and Soak the Carburetor Overnight in Carburetor Cleaner (I Use Gunk). I have Found that Most People can Use a Breakdown/IPL and Disassemble the Carburetor Enough for Proper Cleaning. You Only have to Remove the Bowl, Float Pin, Float and Needle Valve and Any Adjustment Screws that Go Into the Carburetor Body. The Welch Plugs Do Not have to be Removed. Then Soak the Carburetor Body and Parts in a 1 Gallon Can of Gunk Carburetor Cleaner Overnight. The Can has a Parts Tray Inside it for the Small Parts. Once the Carburetor and Parts are in the Cleaner, you can Replace the Lid for Safety and to Prevent Accidental Spillage. Then Blow Out the Passages with Compressed Air. Install New Parts if Required. What is the Cylinder Compression? Check the Flywheel Key. If the Flywheel Key is Damaged, then the ENgine will have Compression, Gas and Fire, but Still will Not Start and Run. The Flywheel Key Times the Plug Firing to the Piston Location During Compression Stroke. You can View a Breakdown/IPL of this Engine at this Site Addy, http://www.smallenginepartswarehouse.com/parts.asp and Select the Shop Online Parts Look Up. Then Select the Model Tab. Then Select the OEM and Enter the Model Numbers CV490S-27508. Then Double Click on the Model in the Results Area. Now you can Select the Section of the Engine you Wish to View. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. 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 9pm EST (US). My New Day Starts then. Thanks.

Respectfully

John

---------- FOLLOW-UP ----------

QUESTION: Hi John,
I tried spraying starter fluid into the carb - no luck. Because I only sprayed the carb w/ a can of Gumout, I got a gallon can of cleaner and recleaned. Reassembled it will not start - engine turns over with an occasional backfire. Is there any chance there is some valve problem? I guess I'm looking for another answer as I'm unclear how the flywheel key can be damaged. Do these break or can they partially shear?  I spun the engine by hand and can feel the compression (and lack of compression when I removed the spark plug) so I'm unclear why the key could be the culprit. Is it possible that it is some ignition module or the coil is just not strong enough?
Thanks in advance for the help,
Ken

Answer
Hello Again Ken:

The Flywheel Key can Partially Shear. This Throws the Spark Plug Timing Off. The Flywheel Keys Purpose is to Time the Plug Firing with the Position of the Piston in the Cylinder During the Power (compression) Stroke. The Crankshaft and Ca Timing Marks Set the Valve Timing for the Engine. The Flywheel Key Does Not Hold the Flywheel to the Crankshaft. The Torque on the Flywheel Nut Holds the Flywheel. The Key is For Timing the Plug ONLY. If the Key is Damaged it will Cause the Backfire you Described Due to the Plug Firing at the Improper Time. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.

Good Luck

Respectfully

John