Small Engines (Lawn Mowers, etc.): poor running kohler, fly wheel, plug gap

Question
Morning Eric here is the additional info you asked for;
Model cv15s
Spec  41567
Family SKH426U1G2RB
S/N    2725120014

I doubled check and its a Champion plug RC12YC and is to be gapped at.040".

When I did my "maintenance" I used my compressor and blew all the grass and dirt off. Any chance something loosened?

How does one pop the fly wheel off? If you think I should check the key. Thanks for answering me, Bob
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Followup To
Question -
I recently did some routine maintenance, oil and filter change, air filter, spark plug, and fuel filter. Now it runs pourly. I tripled checked the gap.040 and even bought another plug. Put fresh gas in still pour running. In the past 2 months I replaced the starter too. When I start the engine, it sputters and dies as the starter cranks. If I keep cranking it does turn over and at high speed doesn't seem to run pourly. If I throttle down it runs pourly and I can hear knocking in the fly wheel housing. When I shut it off there is a slight wooshing sound. I was planning to pull the fly wheel off and check the keys, but I'm really unsure if that is the right thing to do and am not sure of the process.

Answer -
What is you engine model number?  All the engines in the manual call for 0.025 to 0.035 plug gap.

Where did you find 0.040 gap?  Are my manuals out of date?
Let me know.
Eric

Answer
Try gapping the spark plug to .035.

Does the engine oil smell like gasoline?  I recently had a Kohler leak gas into the crankcase.  The inlet needle was leaking causing gas to enter the crankcase.  Overhauled the carb and fixed the problem.

Let me know what the oil smells like.  Also, keep an eye on the fuel level.  If you notice the fuel decreasing without using the mower then the carb inlet needle must be leaking.
Let me know what you find.
Eric