Small Engines (Lawn Mowers, etc.): Kawasaki 14HP on JD lawn tractor, main bearings, head gasket

Question
My JD LX176 lawn tractor has a 14HP Kawasaki (code# FC420V-AS10).  It has run flawlessly for 14 years and I maintain it well.  Recently, it has developed a starting issue after the engine reaches operating temp.  After running a while and then shutting down, it will not start again until the engine has cooled (for at least an hour).  

Operating the starter when the engine is hot often but not always produces a backfire and there is a faint smell of raw gasoline so there must be some flooding.

No problem starting when cold & as long as I keep the engine running I detect no performance problems.

Can you give me some suggestions on what to try before I start taking things apart?


Answer
I think you need a valve job and new head gasket.  Reseat the valves and readjust the clearance.  That is a ball bearing engine so the main bearings are replaceable.  You may look at doing that too.  Other than that it could be the coil breaking down when it gets hot.