Small Engines (Lawn Mowers, etc.): Murray w/B&S 4.5HP, head gasket, murray mower

Question
I have a Murray mower about 2 years old.  At the end of last year's mowing season it wouldn't start.  I had no previous problems and it typically started on the first try.  I thought the tube from the carb going into the tank was clogged so I removed the carb and spray everything with cleaner.  I put the carb back on and I assumed that fixed the problem.  This year I've noticed that it runs fine and dies now and then.  Lately it has been more and more frequent and I've started to think it's heat related.  I've also found some oil in the carb.  I took most of the motor apart tonight.  I didn't find anything out of the ordinary.  I'm wondering if too much oil is in the compartment with the valve springs and is being sucked into the tube going to the carb, but I'm not sure.  Any ideas?  I'll have to replace the head gasket as it splintered when I removed the head.  It didn't appear to be leaking though. Thanks.

Answer
Make sure you are using SAE-30 oil.  The valve breather you mentioned will sometimes stick.  You can shake the breather and you should hear it rattle a little.  You can spray some parts cleaner through the valve breather to clean it.

Have you replaced the spark plug?  We see plugs fail often when they warm up. Coils will also show this symptom but they rarely fail these days.

How long will the mower run before it dies?  Will it start right up again or do you have to let it cool?
Let me know.
Eric