Small Engines (Lawn Mowers, etc.): cub cadet lt1018, engine turns over but will not start., engine model type, tic marks

Question
B&S 18.5 hp engine, threw a rod, the rest of the engine was good, put in a new rod, engine will not start,.  I cleaned the carb, check to see that I have good fuel flow, I have a good spark, checked the valve clearance, .005.  Removed the bottom plate to see if the tic marks were lined up, they were.  put small amt of gas in carb throat, did not fire. have a new battery

Answer
Is the flywheel key sheared?  Did follow the strokes before you put the heads on and bolted on the oil sump?  I always do this just to check the valve overlap so I know the engine is properly timed.

What is the engine model, type and code number?  Most of the L head twins have different clearance for the exhaust and intake.

Let me know the engine numbers so I can look up the valve specs.
Eric