Small Engines (Lawn Mowers, etc.): Craftsman Riding Lawnmower Wont Start, spark plug gap, lawn mower wont start

Question
Hi,
Okay, our neighbor moved and gave us a riding lawnmower since he knew my husband is good with fixing things and we sure can use it for our large backyard. It took awhile to start the first time but when it finally did, it was because I used a screwdriver to turn a small screw with a spring on it by the carb. It did not sound good at all but it was running. It has not started again since that day.

My husband is so determined to get it running so I suggested we start simple. We replaced the spark plug and set the gap to .030 and then he removed the carb and cleaned it out. He cleaned the fuel line and put on a new fuel filter.

It turns slowly and then backfires loudly. (I think it is the flywheel) but it spins one direction and then kicks back the other direction. Dont know if thats normal or not so I thought I'd mention that. My husband also says its a weak spark. The spark is a light yellow in color.

It is a Kohler Command 1 and is a 17 HP OHV Craftsman.
Model Number: CV490S (Extended Carb)
Spec No: 27508
Serial No: 3304401363

Any help would be so appreciated!!
Thanks!

Answer
Deena
Thank you for giving me enough information most people just tell me "Uh my lawn mower wont start. whats wrong with it."
Anyway this sounds like the engine is out of timing.
The RC12YC Spark Plug Gap CV490-495 1.02 mm (0.040 in.)is the correct gap.

Check the Ignition Module Air Gap 0.200/0.300 mm (0.0078/0.0118 in.).
Also look at the Flywheel key to see if it has been sheared or is not inline,The old owner may have hit something and sheared the key way.