Small Engines (Lawn Mowers, etc.): Checking Valves on a Briggs and Strantton, crankcase oil, crankcase breather

Question
At what temperature are the valves checked for Clearance?? What is the purpose of a crankcase breather? Can you damage the rod bearing and rods if there is to much crankshaft end play?

Answer
Check the valves when the engine is cold.  The crankcase breather allows crankcase air to exit the crankcase when the piston comes down.  This allows the crankcase to maintain a vaccum preventing the oil and seals from blowing out of the engine.  Too much crankshaft end play could cause premature rod wear but I have never seen this happen.  Briggs sells different crankcase oil sump gaskets so you can obtain the correct end play.

Eric