This engine is on a lawn tractor and suddenly it starts fine, runs for anywhere from 3 to 5 minutes and then suddenly shuts down with a huge cloud of smoke from the exhaust. I restart it and get the same results. Oil level is fine. I removed the OHV cover and a lot of oil mixed with gasoline came out. There are no broken parts visible and the rocker arms, valve springs, etc. appear intact. Any ideas will be appreciated. Thanks

Oil breather.

Thanks but please help me out with the term oil breather and where is it?

How to test a safety switche on a small engine

I can't quite help you out. Go to Briggs and Stratton Lawn Mower Engines - Small Engines & Outboard Motors - Briggs & Stratton (http://www.briggsandstratton.com) and get the diagram from your engine. Look for the oil breather.

In a car the PCV valve helps the crankcase breathe. When it's stuck open, you get rough idle. When it gets stuck closed, gas gets sucked into the oil.

Small engines have something that serves the same purpose. I don't know where it s on your engine.

You'll probably find your air filter full of oil too.

Here is one: http://thumbs.ebaystatic.com/pict/1400019856304040_2.jpg

But, it's probably no where near like the one on your engine.

The breather is easy to find if you follow the black tube that is about 3/8" in diameter from the air filter housing to the crankcase. The breather assembly will be located on the carb. Side of the engine.

I had a engine do the same thing.What mine was,the engine has a luminum push rod on the intake valve and if You log (low gas) these engines they get hot and the bush rod bends enough that the engine will not run.
CHECK THE PUSH RODS!

If the aluminum one was on the intake , it's on the wrong one .