Small Engines (Lawn Mowers, etc.): B&S 18.5 hp making knocking noise, crank case, connecting rod

Question
I have a B&S 18.5 hp Intek plus motor that stopped running abruptly. When trying to restart all it does is make a metallic knocking noise inside the motor. I bought books on repair and have found my way into the crankcase but I dont see anything obvious wrong with it. I was thinking it was the connecting rod but I seem to have misdiagnosed the problem. Any suggestions as to what I have overlooked?

Answer
I take it proper maintenance was done on this engine?  When an engine stops abruptly a couple of things can cause it.  If the engine is low on oil it will cease in typically break a connecting rod.  If this is not the case it could be a piece of equipment the engine is operating..  

Another area to look in his book the halls be sure they are operating properly before the engine is put back together sure it timing marks on the camshaft in the crankshaft gear are properly aligned.  Put the crank case cover back on the bolts in and see if you can turn the engine by hand if you can it is not an internal engine problem.

To be able to diagnose this issue I will need more information on what you were doing before the engine stopped.  Please get back to me with the information.