Small Engines (Lawn Mowers, etc.): B&S 286707, valve tappets, magnatron

Question
Hello Eric,

First, Thank you Very much for providing this service. It is very much appreciated, plus it looks like you are pretty popular.

Replaced a piston in my craftsman rider. Ensured gears were lined up dot-dot. Everything internal was fairly straightforward. Only confusion was how the governor slinger should be installed. I installed it with the retractable pin right against (Not on either side) the gauge extending inside the housing. Other side over the Cam, no spring clip or anything. Oil pan housing resting on top of that.

Buttoned everything up. New starter, new magnatron and battery and plug. Sucker spins like a top, but will not start. Got gas, spark and air. When choked, it will backfire through the air cleaner, but no joy. Not sure where to start next. Carb maybe get gunked while getting spun around or do you think I screwed something up internally? Man, I hate to screw up a new set of gaskets...

Much Appreciated  

Answer
Just to confirm the governor system.  When you re-assemlbed the engine, the oil slinger/governor should have sat on top of the camshaft.  The end of the oil slinger/governor should have been resting on the governor arm paddle inside the engine block.

Did you remove the valves or valve tappets when replacing the piston?  Did you rotate the engine by hand before buttonening up the engine and follow the engine strokes to ensure the mechanical timing was correct?  Did you remove the flywheel or crankshaft when replacing the piston?  Is the piston connected to the connecting rod correctly?  What are the valve stem to valve tappet clearances?

A dirty carb can cause the problem but it sounds more like a timing issue.  A sheared flywheel key will cause ignition timing errors and incorrect valve gap can cause mechanical timing errors.

Let me know so we can narrow down the problem.
Eric